diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2025-02-13 15:50:21 +0100 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2025-02-15 17:46:32 +0100 |
| commit | 9aab10a0249eab4ec77c6a5e4f66442610c12a09 (patch) | |
| tree | 87eb2bae7d80588d6e45562faa07d85922e0426d | |
| parent | 5b2fabf7fe8f745ff214ff003e6067b64f172271 (diff) | |
kernfs: Don't re-lock kernfs_root::kernfs_rwsem in kernfs_fop_readdir().
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
1e5289c97bba2 ("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>
| -rw-r--r-- | fs/kernfs/dir.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c index 5f0f8b95f44c..43fbada67838 100644 --- a/fs/kernfs/dir.c +++ b/fs/kernfs/dir.c @@ -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; |