linux-stable/fs/sysv
Tetsuo Handa 674c1c4229 sysv: don't call sb_bread() with pointers_lock held
[ Upstream commit f123dc8638 ]

syzbot is reporting sleep in atomic context in SysV filesystem [1], for
sb_bread() is called with rw_spinlock held.

A "write_lock(&pointers_lock) => read_lock(&pointers_lock) deadlock" bug
and a "sb_bread() with write_lock(&pointers_lock)" bug were introduced by
"Replace BKL for chain locking with sysvfs-private rwlock" in Linux 2.5.12.

Then, "[PATCH] err1-40: sysvfs locking fix" in Linux 2.6.8 fixed the
former bug by moving pointers_lock lock to the callers, but instead
introduced a "sb_bread() with read_lock(&pointers_lock)" bug (which made
this problem easier to hit).

Al Viro suggested that why not to do like get_branch()/get_block()/
find_shared() in Minix filesystem does. And doing like that is almost a
revert of "[PATCH] err1-40: sysvfs locking fix" except that get_branch()
 from with find_shared() is called without write_lock(&pointers_lock).

Reported-by: syzbot <syzbot+69b40dc5fd40f32c199f@syzkaller.appspotmail.com>
Link: https://syzkaller.appspot.com/bug?extid=69b40dc5fd40f32c199f
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Link: https://lore.kernel.org/r/0d195f93-a22a-49a2-0020-103534d6f7f6@I-love.SAKURA.ne.jp
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2024-04-13 12:59:45 +02:00
..
Kconfig docs: filesystems: fix renamed references 2020-04-20 15:45:22 -06:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
balloc.c
dir.c
file.c
ialloc.c
inode.c [PATCH] reduce boilerplate in fsid handling 2020-09-18 16:45:50 -04:00
itree.c sysv: don't call sb_bread() with pointers_lock held 2024-04-13 12:59:45 +02:00
namei.c sysv: bury the broken "quietly truncate the long filenames" logics 2019-04-09 19:21:06 -04:00
super.c fs: sysv: Initialize filesystem timestamp ranges 2019-08-30 07:27:18 -07:00
sysv.h sysv: bury the broken "quietly truncate the long filenames" logics 2019-04-09 19:21:06 -04:00