github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-23 14:42:08 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

kernfs: Don't re-lock kernfs_root::kernfs_rwsem in kernfs_fop_readdir().

Browse Source 
The readdir operation iterates over all entries and invokes dir_emit()
for every entry passing kernfs_node::name as argument.
Since the name argument can change, and become invalid, the
kernfs_root::kernfs_rwsem lock should not be dropped to prevent renames
during the operation.

The lock drop around dir_emit() has been initially introduced in commit
   1e5289c97b ("sysfs: Cache the last sysfs_dirent to improve readdir scalability v2")

to avoid holding a global lock during a page fault. The lock drop is
wrong since the support of renames and not a big burden since the lock
is no longer global.

Don't re-acquire kernfs_root::kernfs_rwsem while copying the name to the
userpace buffer.

Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20250213145023.2820193-5-bigeasy@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sebastian Andrzej Siewior 2025-02-13 15:50:21 +01:00 committed by Greg Kroah-Hartman
parent 5b2fabf7fe
commit 9aab10a024
1 changed files with 3 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
fs/kernfs/dir.c
View File

@ -1869,10 +1869,10 @@ static int kernfs_fop_readdir(struct file *file, struct dir_context *ctx)
file->private_data = pos;
kernfs_get(pos);
up_read(&root->kernfs_rwsem);
if (!dir_emit(ctx, name, len, ino, type))
if (!dir_emit(ctx, name, len, ino, type)) {
up_read(&root->kernfs_rwsem);
return 0;
down_read(&root->kernfs_rwsem);
}
}
up_read(&root->kernfs_rwsem);
file->private_data = NULL;