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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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7f78e03513
Modify the request_module to prefix the file system type with "fs-" and add aliases to all of the filesystems that can be built as modules to match. A common practice is to build all of the kernel code and leave code that is not commonly needed as modules, with the result that many users are exposed to any bug anywhere in the kernel. Looking for filesystems with a fs- prefix limits the pool of possible modules that can be loaded by mount to just filesystems trivially making things safer with no real cost. Using aliases means user space can control the policy of which filesystem modules are auto-loaded by editing /etc/modprobe.d/*.conf with blacklist and alias directives. Allowing simple, safe, well understood work-arounds to known problematic software. This also addresses a rare but unfortunate problem where the filesystem name is not the same as it's module name and module auto-loading would not work. While writing this patch I saw a handful of such cases. The most significant being autofs that lives in the module autofs4. This is relevant to user namespaces because we can reach the request module in get_fs_type() without having any special permissions, and people get uncomfortable when a user specified string (in this case the filesystem type) goes all of the way to request_module. After having looked at this issue I don't think there is any particular reason to perform any filtering or permission checks beyond making it clear in the module request that we want a filesystem module. The common pattern in the kernel is to call request_module() without regards to the users permissions. In general all a filesystem module does once loaded is call register_filesystem() and go to sleep. Which means there is not much attack surface exposed by loading a filesytem module unless the filesystem is mounted. In a user namespace filesystems are not mounted unless .fs_flags = FS_USERNS_MOUNT, which most filesystems do not set today. Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Acked-by: Kees Cook <keescook@chromium.org> Reported-by: Kees Cook <keescook@google.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
742 lines
15 KiB
C
742 lines
15 KiB
C
/*
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* binfmt_misc.c
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*
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* Copyright (C) 1997 Richard Günther
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*
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* binfmt_misc detects binaries via a magic or filename extension and invokes
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* a specified wrapper. This should obsolete binfmt_java, binfmt_em86 and
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* binfmt_mz.
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*
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* 1997-04-25 first version
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* [...]
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* 1997-05-19 cleanup
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* 1997-06-26 hpa: pass the real filename rather than argv[0]
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* 1997-06-30 minor cleanup
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* 1997-08-09 removed extension stripping, locking cleanup
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* 2001-02-28 AV: rewritten into something that resembles C. Original didn't.
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*/
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/sched.h>
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#include <linux/magic.h>
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#include <linux/binfmts.h>
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#include <linux/slab.h>
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#include <linux/ctype.h>
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#include <linux/file.h>
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#include <linux/pagemap.h>
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#include <linux/namei.h>
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#include <linux/mount.h>
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#include <linux/syscalls.h>
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#include <linux/fs.h>
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#include <asm/uaccess.h>
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enum {
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VERBOSE_STATUS = 1 /* make it zero to save 400 bytes kernel memory */
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};
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static LIST_HEAD(entries);
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static int enabled = 1;
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enum {Enabled, Magic};
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#define MISC_FMT_PRESERVE_ARGV0 (1<<31)
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#define MISC_FMT_OPEN_BINARY (1<<30)
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#define MISC_FMT_CREDENTIALS (1<<29)
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typedef struct {
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struct list_head list;
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unsigned long flags; /* type, status, etc. */
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int offset; /* offset of magic */
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int size; /* size of magic/mask */
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char *magic; /* magic or filename extension */
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char *mask; /* mask, NULL for exact match */
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char *interpreter; /* filename of interpreter */
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char *name;
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struct dentry *dentry;
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} Node;
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static DEFINE_RWLOCK(entries_lock);
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static struct file_system_type bm_fs_type;
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static struct vfsmount *bm_mnt;
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static int entry_count;
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/*
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* Check if we support the binfmt
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* if we do, return the node, else NULL
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* locking is done in load_misc_binary
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*/
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static Node *check_file(struct linux_binprm *bprm)
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{
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char *p = strrchr(bprm->interp, '.');
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struct list_head *l;
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list_for_each(l, &entries) {
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Node *e = list_entry(l, Node, list);
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char *s;
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int j;
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if (!test_bit(Enabled, &e->flags))
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continue;
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if (!test_bit(Magic, &e->flags)) {
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if (p && !strcmp(e->magic, p + 1))
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return e;
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continue;
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}
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s = bprm->buf + e->offset;
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if (e->mask) {
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for (j = 0; j < e->size; j++)
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if ((*s++ ^ e->magic[j]) & e->mask[j])
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break;
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} else {
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for (j = 0; j < e->size; j++)
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if ((*s++ ^ e->magic[j]))
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break;
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}
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if (j == e->size)
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return e;
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}
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return NULL;
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}
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/*
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* the loader itself
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*/
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static int load_misc_binary(struct linux_binprm *bprm)
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{
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Node *fmt;
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struct file * interp_file = NULL;
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char iname[BINPRM_BUF_SIZE];
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const char *iname_addr = iname;
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int retval;
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int fd_binary = -1;
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retval = -ENOEXEC;
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if (!enabled)
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goto _ret;
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/* to keep locking time low, we copy the interpreter string */
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read_lock(&entries_lock);
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fmt = check_file(bprm);
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if (fmt)
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strlcpy(iname, fmt->interpreter, BINPRM_BUF_SIZE);
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read_unlock(&entries_lock);
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if (!fmt)
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goto _ret;
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if (!(fmt->flags & MISC_FMT_PRESERVE_ARGV0)) {
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retval = remove_arg_zero(bprm);
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if (retval)
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goto _ret;
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}
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if (fmt->flags & MISC_FMT_OPEN_BINARY) {
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/* if the binary should be opened on behalf of the
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* interpreter than keep it open and assign descriptor
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* to it */
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fd_binary = get_unused_fd();
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if (fd_binary < 0) {
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retval = fd_binary;
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goto _ret;
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}
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fd_install(fd_binary, bprm->file);
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/* if the binary is not readable than enforce mm->dumpable=0
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regardless of the interpreter's permissions */
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would_dump(bprm, bprm->file);
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allow_write_access(bprm->file);
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bprm->file = NULL;
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/* mark the bprm that fd should be passed to interp */
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bprm->interp_flags |= BINPRM_FLAGS_EXECFD;
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bprm->interp_data = fd_binary;
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} else {
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allow_write_access(bprm->file);
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fput(bprm->file);
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bprm->file = NULL;
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}
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/* make argv[1] be the path to the binary */
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retval = copy_strings_kernel (1, &bprm->interp, bprm);
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if (retval < 0)
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goto _error;
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bprm->argc++;
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/* add the interp as argv[0] */
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retval = copy_strings_kernel (1, &iname_addr, bprm);
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if (retval < 0)
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goto _error;
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bprm->argc ++;
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/* Update interp in case binfmt_script needs it. */
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retval = bprm_change_interp(iname, bprm);
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if (retval < 0)
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goto _error;
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interp_file = open_exec (iname);
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retval = PTR_ERR (interp_file);
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if (IS_ERR (interp_file))
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goto _error;
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bprm->file = interp_file;
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if (fmt->flags & MISC_FMT_CREDENTIALS) {
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/*
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* No need to call prepare_binprm(), it's already been
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* done. bprm->buf is stale, update from interp_file.
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*/
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memset(bprm->buf, 0, BINPRM_BUF_SIZE);
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retval = kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
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} else
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retval = prepare_binprm (bprm);
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if (retval < 0)
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goto _error;
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retval = search_binary_handler(bprm);
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if (retval < 0)
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goto _error;
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_ret:
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return retval;
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_error:
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if (fd_binary > 0)
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sys_close(fd_binary);
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bprm->interp_flags = 0;
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bprm->interp_data = 0;
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goto _ret;
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}
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/* Command parsers */
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/*
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* parses and copies one argument enclosed in del from *sp to *dp,
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* recognising the \x special.
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* returns pointer to the copied argument or NULL in case of an
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* error (and sets err) or null argument length.
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*/
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static char *scanarg(char *s, char del)
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{
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char c;
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while ((c = *s++) != del) {
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if (c == '\\' && *s == 'x') {
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s++;
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if (!isxdigit(*s++))
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return NULL;
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if (!isxdigit(*s++))
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return NULL;
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}
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}
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return s;
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}
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static int unquote(char *from)
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{
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char c = 0, *s = from, *p = from;
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while ((c = *s++) != '\0') {
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if (c == '\\' && *s == 'x') {
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s++;
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c = toupper(*s++);
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*p = (c - (isdigit(c) ? '0' : 'A' - 10)) << 4;
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c = toupper(*s++);
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*p++ |= c - (isdigit(c) ? '0' : 'A' - 10);
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continue;
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}
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*p++ = c;
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}
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return p - from;
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}
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static char * check_special_flags (char * sfs, Node * e)
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{
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char * p = sfs;
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int cont = 1;
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/* special flags */
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while (cont) {
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switch (*p) {
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case 'P':
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p++;
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e->flags |= MISC_FMT_PRESERVE_ARGV0;
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break;
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case 'O':
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p++;
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e->flags |= MISC_FMT_OPEN_BINARY;
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break;
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case 'C':
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p++;
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/* this flags also implies the
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open-binary flag */
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e->flags |= (MISC_FMT_CREDENTIALS |
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MISC_FMT_OPEN_BINARY);
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break;
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default:
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cont = 0;
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}
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}
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return p;
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}
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/*
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* This registers a new binary format, it recognises the syntax
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* ':name:type:offset:magic:mask:interpreter:flags'
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* where the ':' is the IFS, that can be chosen with the first char
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*/
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static Node *create_entry(const char __user *buffer, size_t count)
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{
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Node *e;
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int memsize, err;
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char *buf, *p;
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char del;
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/* some sanity checks */
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err = -EINVAL;
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if ((count < 11) || (count > 256))
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goto out;
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err = -ENOMEM;
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memsize = sizeof(Node) + count + 8;
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e = kmalloc(memsize, GFP_USER);
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if (!e)
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goto out;
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p = buf = (char *)e + sizeof(Node);
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memset(e, 0, sizeof(Node));
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if (copy_from_user(buf, buffer, count))
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goto Efault;
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del = *p++; /* delimeter */
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memset(buf+count, del, 8);
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e->name = p;
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p = strchr(p, del);
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if (!p)
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goto Einval;
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*p++ = '\0';
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if (!e->name[0] ||
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!strcmp(e->name, ".") ||
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!strcmp(e->name, "..") ||
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strchr(e->name, '/'))
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goto Einval;
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switch (*p++) {
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case 'E': e->flags = 1<<Enabled; break;
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case 'M': e->flags = (1<<Enabled) | (1<<Magic); break;
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default: goto Einval;
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}
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if (*p++ != del)
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goto Einval;
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if (test_bit(Magic, &e->flags)) {
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char *s = strchr(p, del);
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if (!s)
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goto Einval;
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*s++ = '\0';
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e->offset = simple_strtoul(p, &p, 10);
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if (*p++)
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goto Einval;
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e->magic = p;
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p = scanarg(p, del);
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if (!p)
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goto Einval;
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p[-1] = '\0';
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if (!e->magic[0])
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goto Einval;
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e->mask = p;
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p = scanarg(p, del);
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if (!p)
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goto Einval;
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p[-1] = '\0';
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if (!e->mask[0])
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e->mask = NULL;
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e->size = unquote(e->magic);
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if (e->mask && unquote(e->mask) != e->size)
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goto Einval;
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if (e->size + e->offset > BINPRM_BUF_SIZE)
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goto Einval;
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} else {
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p = strchr(p, del);
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if (!p)
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goto Einval;
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*p++ = '\0';
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e->magic = p;
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p = strchr(p, del);
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if (!p)
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goto Einval;
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|
*p++ = '\0';
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if (!e->magic[0] || strchr(e->magic, '/'))
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goto Einval;
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p = strchr(p, del);
|
|
if (!p)
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|
goto Einval;
|
|
*p++ = '\0';
|
|
}
|
|
e->interpreter = p;
|
|
p = strchr(p, del);
|
|
if (!p)
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|
goto Einval;
|
|
*p++ = '\0';
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|
if (!e->interpreter[0])
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|
goto Einval;
|
|
|
|
|
|
p = check_special_flags (p, e);
|
|
|
|
if (*p == '\n')
|
|
p++;
|
|
if (p != buf + count)
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|
goto Einval;
|
|
return e;
|
|
|
|
out:
|
|
return ERR_PTR(err);
|
|
|
|
Efault:
|
|
kfree(e);
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|
return ERR_PTR(-EFAULT);
|
|
Einval:
|
|
kfree(e);
|
|
return ERR_PTR(-EINVAL);
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|
}
|
|
|
|
/*
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|
* Set status of entry/binfmt_misc:
|
|
* '1' enables, '0' disables and '-1' clears entry/binfmt_misc
|
|
*/
|
|
static int parse_command(const char __user *buffer, size_t count)
|
|
{
|
|
char s[4];
|
|
|
|
if (!count)
|
|
return 0;
|
|
if (count > 3)
|
|
return -EINVAL;
|
|
if (copy_from_user(s, buffer, count))
|
|
return -EFAULT;
|
|
if (s[count-1] == '\n')
|
|
count--;
|
|
if (count == 1 && s[0] == '0')
|
|
return 1;
|
|
if (count == 1 && s[0] == '1')
|
|
return 2;
|
|
if (count == 2 && s[0] == '-' && s[1] == '1')
|
|
return 3;
|
|
return -EINVAL;
|
|
}
|
|
|
|
/* generic stuff */
|
|
|
|
static void entry_status(Node *e, char *page)
|
|
{
|
|
char *dp;
|
|
char *status = "disabled";
|
|
const char * flags = "flags: ";
|
|
|
|
if (test_bit(Enabled, &e->flags))
|
|
status = "enabled";
|
|
|
|
if (!VERBOSE_STATUS) {
|
|
sprintf(page, "%s\n", status);
|
|
return;
|
|
}
|
|
|
|
sprintf(page, "%s\ninterpreter %s\n", status, e->interpreter);
|
|
dp = page + strlen(page);
|
|
|
|
/* print the special flags */
|
|
sprintf (dp, "%s", flags);
|
|
dp += strlen (flags);
|
|
if (e->flags & MISC_FMT_PRESERVE_ARGV0) {
|
|
*dp ++ = 'P';
|
|
}
|
|
if (e->flags & MISC_FMT_OPEN_BINARY) {
|
|
*dp ++ = 'O';
|
|
}
|
|
if (e->flags & MISC_FMT_CREDENTIALS) {
|
|
*dp ++ = 'C';
|
|
}
|
|
*dp ++ = '\n';
|
|
|
|
|
|
if (!test_bit(Magic, &e->flags)) {
|
|
sprintf(dp, "extension .%s\n", e->magic);
|
|
} else {
|
|
int i;
|
|
|
|
sprintf(dp, "offset %i\nmagic ", e->offset);
|
|
dp = page + strlen(page);
|
|
for (i = 0; i < e->size; i++) {
|
|
sprintf(dp, "%02x", 0xff & (int) (e->magic[i]));
|
|
dp += 2;
|
|
}
|
|
if (e->mask) {
|
|
sprintf(dp, "\nmask ");
|
|
dp += 6;
|
|
for (i = 0; i < e->size; i++) {
|
|
sprintf(dp, "%02x", 0xff & (int) (e->mask[i]));
|
|
dp += 2;
|
|
}
|
|
}
|
|
*dp++ = '\n';
|
|
*dp = '\0';
|
|
}
|
|
}
|
|
|
|
static struct inode *bm_get_inode(struct super_block *sb, int mode)
|
|
{
|
|
struct inode * inode = new_inode(sb);
|
|
|
|
if (inode) {
|
|
inode->i_ino = get_next_ino();
|
|
inode->i_mode = mode;
|
|
inode->i_atime = inode->i_mtime = inode->i_ctime =
|
|
current_fs_time(inode->i_sb);
|
|
}
|
|
return inode;
|
|
}
|
|
|
|
static void bm_evict_inode(struct inode *inode)
|
|
{
|
|
clear_inode(inode);
|
|
kfree(inode->i_private);
|
|
}
|
|
|
|
static void kill_node(Node *e)
|
|
{
|
|
struct dentry *dentry;
|
|
|
|
write_lock(&entries_lock);
|
|
dentry = e->dentry;
|
|
if (dentry) {
|
|
list_del_init(&e->list);
|
|
e->dentry = NULL;
|
|
}
|
|
write_unlock(&entries_lock);
|
|
|
|
if (dentry) {
|
|
drop_nlink(dentry->d_inode);
|
|
d_drop(dentry);
|
|
dput(dentry);
|
|
simple_release_fs(&bm_mnt, &entry_count);
|
|
}
|
|
}
|
|
|
|
/* /<entry> */
|
|
|
|
static ssize_t
|
|
bm_entry_read(struct file * file, char __user * buf, size_t nbytes, loff_t *ppos)
|
|
{
|
|
Node *e = file_inode(file)->i_private;
|
|
ssize_t res;
|
|
char *page;
|
|
|
|
if (!(page = (char*) __get_free_page(GFP_KERNEL)))
|
|
return -ENOMEM;
|
|
|
|
entry_status(e, page);
|
|
|
|
res = simple_read_from_buffer(buf, nbytes, ppos, page, strlen(page));
|
|
|
|
free_page((unsigned long) page);
|
|
return res;
|
|
}
|
|
|
|
static ssize_t bm_entry_write(struct file *file, const char __user *buffer,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
struct dentry *root;
|
|
Node *e = file_inode(file)->i_private;
|
|
int res = parse_command(buffer, count);
|
|
|
|
switch (res) {
|
|
case 1: clear_bit(Enabled, &e->flags);
|
|
break;
|
|
case 2: set_bit(Enabled, &e->flags);
|
|
break;
|
|
case 3: root = dget(file->f_path.dentry->d_sb->s_root);
|
|
mutex_lock(&root->d_inode->i_mutex);
|
|
|
|
kill_node(e);
|
|
|
|
mutex_unlock(&root->d_inode->i_mutex);
|
|
dput(root);
|
|
break;
|
|
default: return res;
|
|
}
|
|
return count;
|
|
}
|
|
|
|
static const struct file_operations bm_entry_operations = {
|
|
.read = bm_entry_read,
|
|
.write = bm_entry_write,
|
|
.llseek = default_llseek,
|
|
};
|
|
|
|
/* /register */
|
|
|
|
static ssize_t bm_register_write(struct file *file, const char __user *buffer,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
Node *e;
|
|
struct inode *inode;
|
|
struct dentry *root, *dentry;
|
|
struct super_block *sb = file->f_path.dentry->d_sb;
|
|
int err = 0;
|
|
|
|
e = create_entry(buffer, count);
|
|
|
|
if (IS_ERR(e))
|
|
return PTR_ERR(e);
|
|
|
|
root = dget(sb->s_root);
|
|
mutex_lock(&root->d_inode->i_mutex);
|
|
dentry = lookup_one_len(e->name, root, strlen(e->name));
|
|
err = PTR_ERR(dentry);
|
|
if (IS_ERR(dentry))
|
|
goto out;
|
|
|
|
err = -EEXIST;
|
|
if (dentry->d_inode)
|
|
goto out2;
|
|
|
|
inode = bm_get_inode(sb, S_IFREG | 0644);
|
|
|
|
err = -ENOMEM;
|
|
if (!inode)
|
|
goto out2;
|
|
|
|
err = simple_pin_fs(&bm_fs_type, &bm_mnt, &entry_count);
|
|
if (err) {
|
|
iput(inode);
|
|
inode = NULL;
|
|
goto out2;
|
|
}
|
|
|
|
e->dentry = dget(dentry);
|
|
inode->i_private = e;
|
|
inode->i_fop = &bm_entry_operations;
|
|
|
|
d_instantiate(dentry, inode);
|
|
write_lock(&entries_lock);
|
|
list_add(&e->list, &entries);
|
|
write_unlock(&entries_lock);
|
|
|
|
err = 0;
|
|
out2:
|
|
dput(dentry);
|
|
out:
|
|
mutex_unlock(&root->d_inode->i_mutex);
|
|
dput(root);
|
|
|
|
if (err) {
|
|
kfree(e);
|
|
return -EINVAL;
|
|
}
|
|
return count;
|
|
}
|
|
|
|
static const struct file_operations bm_register_operations = {
|
|
.write = bm_register_write,
|
|
.llseek = noop_llseek,
|
|
};
|
|
|
|
/* /status */
|
|
|
|
static ssize_t
|
|
bm_status_read(struct file *file, char __user *buf, size_t nbytes, loff_t *ppos)
|
|
{
|
|
char *s = enabled ? "enabled\n" : "disabled\n";
|
|
|
|
return simple_read_from_buffer(buf, nbytes, ppos, s, strlen(s));
|
|
}
|
|
|
|
static ssize_t bm_status_write(struct file * file, const char __user * buffer,
|
|
size_t count, loff_t *ppos)
|
|
{
|
|
int res = parse_command(buffer, count);
|
|
struct dentry *root;
|
|
|
|
switch (res) {
|
|
case 1: enabled = 0; break;
|
|
case 2: enabled = 1; break;
|
|
case 3: root = dget(file->f_path.dentry->d_sb->s_root);
|
|
mutex_lock(&root->d_inode->i_mutex);
|
|
|
|
while (!list_empty(&entries))
|
|
kill_node(list_entry(entries.next, Node, list));
|
|
|
|
mutex_unlock(&root->d_inode->i_mutex);
|
|
dput(root);
|
|
default: return res;
|
|
}
|
|
return count;
|
|
}
|
|
|
|
static const struct file_operations bm_status_operations = {
|
|
.read = bm_status_read,
|
|
.write = bm_status_write,
|
|
.llseek = default_llseek,
|
|
};
|
|
|
|
/* Superblock handling */
|
|
|
|
static const struct super_operations s_ops = {
|
|
.statfs = simple_statfs,
|
|
.evict_inode = bm_evict_inode,
|
|
};
|
|
|
|
static int bm_fill_super(struct super_block * sb, void * data, int silent)
|
|
{
|
|
static struct tree_descr bm_files[] = {
|
|
[2] = {"status", &bm_status_operations, S_IWUSR|S_IRUGO},
|
|
[3] = {"register", &bm_register_operations, S_IWUSR},
|
|
/* last one */ {""}
|
|
};
|
|
int err = simple_fill_super(sb, BINFMTFS_MAGIC, bm_files);
|
|
if (!err)
|
|
sb->s_op = &s_ops;
|
|
return err;
|
|
}
|
|
|
|
static struct dentry *bm_mount(struct file_system_type *fs_type,
|
|
int flags, const char *dev_name, void *data)
|
|
{
|
|
return mount_single(fs_type, flags, data, bm_fill_super);
|
|
}
|
|
|
|
static struct linux_binfmt misc_format = {
|
|
.module = THIS_MODULE,
|
|
.load_binary = load_misc_binary,
|
|
};
|
|
|
|
static struct file_system_type bm_fs_type = {
|
|
.owner = THIS_MODULE,
|
|
.name = "binfmt_misc",
|
|
.mount = bm_mount,
|
|
.kill_sb = kill_litter_super,
|
|
};
|
|
MODULE_ALIAS_FS("binfmt_misc");
|
|
|
|
static int __init init_misc_binfmt(void)
|
|
{
|
|
int err = register_filesystem(&bm_fs_type);
|
|
if (!err)
|
|
insert_binfmt(&misc_format);
|
|
return err;
|
|
}
|
|
|
|
static void __exit exit_misc_binfmt(void)
|
|
{
|
|
unregister_binfmt(&misc_format);
|
|
unregister_filesystem(&bm_fs_type);
|
|
}
|
|
|
|
core_initcall(init_misc_binfmt);
|
|
module_exit(exit_misc_binfmt);
|
|
MODULE_LICENSE("GPL");
|