AuxXxilium/linux_dsm_epyc7002
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kill struct filename.separate

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just make const char iname[] the last member and compare name->name with
name->iname instead of checking name->separate

We need to make sure that out-of-line name doesn't end up allocated adjacent
to struct filename refering to it; fortunately, it's easy to achieve - just
allocate that struct filename with one byte in ->iname[], so that ->iname[0]
will be inside the same object and thus have an address different from that
of out-of-line name [spotted by Boqun Feng <boqun.feng@gmail.com>]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2015-02-22 20:07:13 -05:00
parent 6e8a1f8741
commit fd2f7cb5bc
2 changed files with 17 additions and 14 deletions
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29
fs/namei.c
View File

@ -119,7 +119,7 @@
* PATH_MAX includes the nul terminator --RR.
*/
#define EMBEDDED_NAME_MAX (PATH_MAX - sizeof(struct filename))
#define EMBEDDED_NAME_MAX (PATH_MAX - offsetof(struct filename, iname))
struct filename *
getname_flags(const char __user *filename, int flags, int *empty)
@ -140,9 +140,8 @@ getname_flags(const char __user *filename, int flags, int *empty)
* First, try to embed the struct filename inside the names_cache
* allocation
*/
kname = (char *)result + sizeof(*result);
kname = (char *)result->iname;
result->name = kname;
result->separate = false;
len = strncpy_from_user(kname, filename, EMBEDDED_NAME_MAX);
if (unlikely(len < 0)) {
@ -157,15 +156,20 @@ getname_flags(const char __user *filename, int flags, int *empty)
* userland.
*/
if (unlikely(len == EMBEDDED_NAME_MAX)) {
const size_t size = offsetof(struct filename, iname[1]);
kname = (char *)result;
result = kzalloc(sizeof(*result), GFP_KERNEL);
/*
* size is chosen that way we to guarantee that
* result->iname[0] is within the same object and that
* kname can't be equal to result->iname, no matter what.
*/
result = kzalloc(size, GFP_KERNEL);
if (unlikely(!result)) {
__putname(kname);
return ERR_PTR(-ENOMEM);
}
result->name = kname;
result->separate = true;
len = strncpy_from_user(kname, filename, PATH_MAX);
if (unlikely(len < 0)) {
__putname(kname);
@ -213,8 +217,7 @@ getname_kernel(const char * filename)
return ERR_PTR(-ENOMEM);
if (len <= EMBEDDED_NAME_MAX) {
result->name = (char *)(result) + sizeof(*result);
result->separate = false;
result->name = (char *)result->iname;
} else if (len <= PATH_MAX) {
struct filename *tmp;
@ -224,7 +227,6 @@ getname_kernel(const char * filename)
return ERR_PTR(-ENOMEM);
}
tmp->name = (char *)result;
tmp->separate = true;
result = tmp;
} else {
__putname(result);
@ -246,7 +248,7 @@ void putname(struct filename *name)
if (--name->refcnt > 0)
return;
if (name->separate) {
if (name->name != name->iname) {
__putname(name->name);
kfree(name);
} else
@ -1852,6 +1854,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
struct nameidata *nd)
{
int retval = 0;
const char *s = name->name;
nd->last_type = LAST_ROOT; /* if there are only slashes... */
nd->flags = flags | LOOKUP_JUMPED | LOOKUP_PARENT;
@ -1860,7 +1863,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
if (flags & LOOKUP_ROOT) {
struct dentry *root = nd->root.dentry;
struct inode *inode = root->d_inode;
if (name->name[0]) {
if (*s) {
if (!d_can_lookup(root))
return -ENOTDIR;
retval = inode_permission(inode, MAY_EXEC);
@ -1882,7 +1885,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
nd->root.mnt = NULL;
nd->m_seq = read_seqbegin(&mount_lock);
if (name->name[0] == '/') {
if (*s == '/') {
if (flags & LOOKUP_RCU) {
rcu_read_lock();
nd->seq = set_root_rcu(nd);
@ -1916,7 +1919,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
dentry = f.file->f_path.dentry;
if (name->name[0]) {
if (*s) {
if (!d_can_lookup(dentry)) {
fdput(f);
return -ENOTDIR;
@ -1946,7 +1949,7 @@ static int path_init(int dfd, const struct filename *name, unsigned int flags,
return -ECHILD;
done:
current->total_link_count = 0;
return link_path_walk(name->name, nd);
return link_path_walk(s, nd);
}
static void path_cleanup(struct nameidata *nd)

2
include/linux/fs.h
View File

@ -2144,7 +2144,7 @@ struct filename {
const __user char *uptr; /* original userland pointer */
struct audit_names *aname;
int refcnt;
bool separate; /* should "name" be freed? */
const char iname[];
};
extern long vfs_truncate(struct path *, loff_t);