3.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: Linus Torvalds <[email protected]> commit 0640113be25d283e0ff77a9f041e1242182387f0 upstream. Cyrill Gorcunov reports that I broke the fdinfo files with commit 30a08bf2d31d ("proc: move fd symlink i_mode calculations into tid_fd_revalidate()"), and he's quite right. The tid_fd_revalidate() function is not just used for the <tid>/fd symlinks, it's also used for the <tid>/fdinfo/<fd> files, and the permission model for those are different. So do the dynamic symlink permission handling just for symlinks, making the fdinfo files once more appear as the proper regular files they are. Of course, Al Viro argued (probably correctly) that we shouldn't do the symlink permission games at all, and make the symlinks always just be the normal 'lrwxrwxrwx'. That would have avoided this issue too, but since somebody noticed that the permissions had changed (which was the reason for that original commit 30a08bf2d31d in the first place), people do apparently use this feature. [ Basically, you can use the symlink permission data as a cheap "fdinfo" replacement, since you see whether the file is open for reading and/or writing by just looking at st_mode of the symlink. So the feature does make sense, even if the pain it has caused means we probably shouldn't have done it to begin with. ] Reported-and-tested-by: Cyrill Gorcunov <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/proc/base.c | 17 ++++++++++------- 1 file changed, 10 insertions(+), 7 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1803,7 +1803,7 @@ static int tid_fd_revalidate(struct dent rcu_read_lock(); file = fcheck_files(files, fd); if (file) { - unsigned i_mode, f_mode = file->f_mode; + unsigned f_mode = file->f_mode; rcu_read_unlock(); put_files_struct(files); @@ -1819,12 +1819,14 @@ static int tid_fd_revalidate(struct dent inode->i_gid = 0; } - 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; + 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); @@ -1859,6 +1861,7 @@ static struct dentry *proc_fd_instantiat ei = PROC_I(inode); ei->fd = fd; + inode->i_mode = S_IFLNK; inode->i_op = &proc_pid_link_inode_operations; inode->i_size = 64; ei->op.proc_get_link = proc_fd_link; -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
