]> www.infradead.org Git - users/jedix/linux-maple.git/commit
kernfs: Don't re-lock kernfs_root::kernfs_rwsem in kernfs_fop_readdir().
authorSebastian Andrzej Siewior <bigeasy@linutronix.de>
Thu, 13 Feb 2025 14:50:21 +0000 (15:50 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 15 Feb 2025 16:46:32 +0000 (17:46 +0100)
commit9aab10a0249eab4ec77c6a5e4f66442610c12a09
tree87eb2bae7d80588d6e45562faa07d85922e0426d
parent5b2fabf7fe8f745ff214ff003e6067b64f172271
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>
fs/kernfs/dir.c