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authorLinus Torvalds <torvalds@linux-foundation.org>2012-05-18 11:32:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-18 14:06:17 -0700
commit30a08bf2d31d275c6fc71dd1811342777e95c831 (patch)
tree541e4d439b73accdaa48bf48fc77a1915555439b /fs
parent3d9944978e0bb6c98b901949cb7a22256e48b23d (diff)
downloadlinux-linaro-stable-30a08bf2d31d275c6fc71dd1811342777e95c831.tar.gz
proc: move fd symlink i_mode calculations into tid_fd_revalidate()
Instead of doing the i_mode calculations at proc_fd_instantiate() time, move them into tid_fd_revalidate(), which is where the other inode state (notably uid/gid information) is updated too. Otherwise we'll end up with stale i_mode information if an fd is re-used while the dentry still hangs around. Not that anything really *cares* (symlink permissions don't really matter), but Tetsuo Handa noticed that the owner read/write bits don't always match the state of the readability of the file descriptor, and we _used_ to get this right a long time ago in a galaxy far, far away. Besides, aside from fixing an ugly detail (that has apparently been this way since commit 61a28784028e: "proc: Remove the hard coded inode numbers" in 2006), this removes more lines of code than it adds. And it just makes sense to update i_mode in the same place we update i_uid/gid. Al Viro correctly points out that we could just do the inode fill in the inode iops ->getattr() function instead. However, that does require somewhat slightly more invasive changes, and adds yet *another* lookup of the file descriptor. We need to do the revalidate() for other reasons anyway, and have the file descriptor handy, so we might as well fill in the information at this point. Reported-by: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> Cc: Al Viro <viro@zeniv.linux.org.uk> Acked-by: Eric Biederman <ebiederm@xmission.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs')
-rw-r--r--fs/proc/base.c43
1 files changed, 14 insertions, 29 deletions
diff --git a/fs/proc/base.c b/fs/proc/base.c
index 1c8b280146d7..7d6ad98631f2 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1799,10 +1799,15 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
if (task) {
files = get_files_struct(task);
if (files) {
+ struct file *file;
rcu_read_lock();
- if (fcheck_files(files, fd)) {
+ file = fcheck_files(files, fd);
+ if (file) {
+ unsigned i_mode, f_mode = file->f_mode;
+
rcu_read_unlock();
put_files_struct(files);
+
if (task_dumpable(task)) {
rcu_read_lock();
cred = __task_cred(task);
@@ -1813,7 +1818,14 @@ static int tid_fd_revalidate(struct dentry *dentry, struct nameidata *nd)
inode->i_uid = 0;
inode->i_gid = 0;
}
- inode->i_mode &= ~(S_ISUID | S_ISGID);
+
+ 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;
@@ -1837,8 +1849,6 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
struct dentry *dentry, struct task_struct *task, const void *ptr)
{
unsigned fd = *(const unsigned *)ptr;
- struct file *file;
- struct files_struct *files;
struct inode *inode;
struct proc_inode *ei;
struct dentry *error = ERR_PTR(-ENOENT);
@@ -1848,25 +1858,6 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
goto out;
ei = PROC_I(inode);
ei->fd = fd;
- files = get_files_struct(task);
- if (!files)
- goto out_iput;
- inode->i_mode = S_IFLNK;
-
- /*
- * We are not taking a ref to the file structure, so we must
- * hold ->file_lock.
- */
- spin_lock(&files->file_lock);
- file = fcheck_files(files, fd);
- if (!file)
- goto out_unlock;
- if (file->f_mode & FMODE_READ)
- inode->i_mode |= S_IRUSR | S_IXUSR;
- if (file->f_mode & FMODE_WRITE)
- inode->i_mode |= S_IWUSR | S_IXUSR;
- spin_unlock(&files->file_lock);
- put_files_struct(files);
inode->i_op = &proc_pid_link_inode_operations;
inode->i_size = 64;
@@ -1879,12 +1870,6 @@ static struct dentry *proc_fd_instantiate(struct inode *dir,
out:
return error;
-out_unlock:
- spin_unlock(&files->file_lock);
- put_files_struct(files);
-out_iput:
- iput(inode);
- goto out;
}
static struct dentry *proc_lookupfd_common(struct inode *dir,