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proc_lookupfd_common(): don't bother with instantiate unless the file is open

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... and take the "check if file is open, pick ->f_mode" into a helper;
tid_fd_revalidate() can use it.

The next patch will get rid of tid_fd_revalidate() calls in instantiate
callbacks.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2018-05-02 22:42:22 -04:00
parent 1bbc55131e
commit 1ae9bd8b7e
1 changed files with 33 additions and 28 deletions
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61
fs/proc/fd.c
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@ -81,12 +81,29 @@ static const struct file_operations proc_fdinfo_file_operations = {
.release = single_release,
};
static bool tid_fd_mode(struct task_struct *task, unsigned fd, fmode_t *mode)
{
struct files_struct *files = get_files_struct(task);
struct file *file;
if (!files)
return false;
rcu_read_lock();
file = fcheck_files(files, fd);
if (file)
*mode = file->f_mode;
rcu_read_unlock();
put_files_struct(files);
return !!file;
}
static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
{
struct files_struct *files;
struct task_struct *task;
struct inode *inode;
unsigned int fd;
fmode_t f_mode;
if (flags & LOOKUP_RCU)
return -ECHILD;
@ -96,35 +113,20 @@ static int tid_fd_revalidate(struct dentry *dentry, unsigned int flags)
fd = proc_fd(inode);
if (task) {
files = get_files_struct(task);
if (files) {
struct file *file;
if (tid_fd_mode(task, fd, &f_mode)) {
task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
rcu_read_lock();
file = fcheck_files(files, fd);
if (file) {
unsigned f_mode = file->f_mode;
rcu_read_unlock();
put_files_struct(files);
task_dump_owner(task, 0, &inode->i_uid, &inode->i_gid);
if (S_ISLNK(inode->i_mode)) {
unsigned i_mode = S_IFLNK;
if (f_mode & FMODE_READ)
i_mode |= S_IRUSR | S_IXUSR;
if (f_mode & FMODE_WRITE)
i_mode |= S_IWUSR | S_IXUSR;
inode->i_mode = i_mode;
}
security_task_to_inode(task, inode);
put_task_struct(task);
return 1;
if (S_ISLNK(inode->i_mode)) {
unsigned i_mode = S_IFLNK;
if (f_mode & FMODE_READ)
i_mode |= S_IRUSR | S_IXUSR;
if (f_mode & FMODE_WRITE)
i_mode |= S_IWUSR | S_IXUSR;
inode->i_mode = i_mode;
}
rcu_read_unlock();
put_files_struct(files);
security_task_to_inode(task, inode);
put_task_struct(task);
return 1;
}
put_task_struct(task);
}
@ -203,11 +205,14 @@ static struct dentry *proc_lookupfd_common(struct inode *dir,
struct task_struct *task = get_proc_task(dir);
int result = -ENOENT;
unsigned fd = name_to_int(&dentry->d_name);
fmode_t f_mode;
if (!task)
goto out_no_task;
if (fd == ~0U)
goto out;
if (!tid_fd_mode(task, fd, &f_mode))
goto out;
result = instantiate(dir, dentry, task, (void *)(unsigned long)fd);
out: