Neel Natu 679bce55ab kernfs: fix false-positive WARN(nr_mmapped) in kernfs_drain_open_files ... [ Upstream commit 05d8f25586 ] Prior to this change 'on->nr_mmapped' tracked the total number of mmaps across all of its associated open files via kernfs_fop_mmap(). Thus if the file descriptor associated with a kernfs_open_file was mmapped 10 times then we would have: 'of->mmapped = true' and 'of_on(of)->nr_mmapped = 10'. The problem is that closing or draining a 'of->mmapped' file would only decrement one from the 'of_on(of)->nr_mmapped' counter. For e.g. we have this from kernfs_unlink_open_file(): if (of->mmapped) on->nr_mmapped--; The WARN_ON_ONCE(on->nr_mmapped) in kernfs_drain_open_files() is easy to reproduce by: 1. opening a (mmap-able) kernfs file. 2. mmap-ing that file more than once (mapping just once masks the issue). 3. trigger a drain of that kernfs file. Modulo out-of-tree patches I was able to trigger this reliably by identifying pci device nodes in sysfs that have resource regions that are mmap-able and that don't have any driver attached to them (steps 1 and 2). For step 3 we can "echo 1 > remove" to trigger a kernfs_drain. Signed-off-by: Neel Natu <neelnatu@google.com> Link: https://lore.kernel.org/r/20240127234636.609265-1-neelnatu@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>		2024-08-29 17:30:35 +02:00
..
dir.c	kernfs: Convert kernfs_path_from_node_locked() from strlcpy() to strscpy()	2024-08-03 08:48:54 +02:00
file.c	kernfs: fix false-positive WARN(nr_mmapped) in kernfs_drain_open_files	2024-08-29 17:30:35 +02:00
inode.c	kernfs: fix all kernel-doc warnings and multiple typos	2024-08-03 08:48:54 +02:00
Kconfig	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
kernfs-internal.h	kernfs: fix all kernel-doc warnings and multiple typos	2024-08-03 08:48:54 +02:00
Makefile	treewide: Add SPDX license identifier - Makefile/Kconfig	2019-05-21 10:50:46 +02:00
mount.c	kernfs: fix all kernel-doc warnings and multiple typos	2024-08-03 08:48:54 +02:00
symlink.c	kernfs: fix all kernel-doc warnings and multiple typos	2024-08-03 08:48:54 +02:00