1fb112cefa
[ Upstream commit 05d8f255867e3196565bb31a911a437697fab094 ]
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>
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| Kconfig | ||
| Makefile | ||
| dir.c | ||
| file.c | ||
| inode.c | ||
| kernfs-internal.h | ||
| mount.c | ||
| symlink.c | ||