6.15-stable review patch. If anyone has any objections, please let me know.
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From: Yangtao Li frank.li@vivo.com
[ Upstream commit fcb96956c921f1aae7e7b477f2435c56f77a31b4 ]
Syzbot reported an issue in hfsplus filesystem:
------------[ cut here ]------------ WARNING: CPU: 0 PID: 4400 at fs/hfsplus/extents.c:346 hfsplus_free_extents+0x700/0xad0 Call Trace: <TASK> hfsplus_file_truncate+0x768/0xbb0 fs/hfsplus/extents.c:606 hfsplus_write_begin+0xc2/0xd0 fs/hfsplus/inode.c:56 cont_expand_zero fs/buffer.c:2383 [inline] cont_write_begin+0x2cf/0x860 fs/buffer.c:2446 hfsplus_write_begin+0x86/0xd0 fs/hfsplus/inode.c:52 generic_cont_expand_simple+0x151/0x250 fs/buffer.c:2347 hfsplus_setattr+0x168/0x280 fs/hfsplus/inode.c:263 notify_change+0xe38/0x10f0 fs/attr.c:420 do_truncate+0x1fb/0x2e0 fs/open.c:65 do_sys_ftruncate+0x2eb/0x380 fs/open.c:193 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
To avoid deadlock, Commit 31651c607151 ("hfsplus: avoid deadlock on file truncation") unlock extree before hfsplus_free_extents(), and add check wheather extree is locked in hfsplus_free_extents().
However, when operations such as hfsplus_file_release, hfsplus_setattr, hfsplus_unlink, and hfsplus_get_block are executed concurrently in different files, it is very likely to trigger the WARN_ON, which will lead syzbot and xfstest to consider it as an abnormality.
The comment above this warning also describes one of the easy triggering situations, which can easily trigger and cause xfstest&syzbot to report errors.
[task A] [task B] ->hfsplus_file_release ->hfsplus_file_truncate ->hfs_find_init ->mutex_lock ->mutex_unlock ->hfsplus_write_begin ->hfsplus_get_block ->hfsplus_file_extend ->hfsplus_ext_read_extent ->hfs_find_init ->mutex_lock ->hfsplus_free_extents WARN_ON(mutex_is_locked) !!!
Several threads could try to lock the shared extents tree. And warning can be triggered in one thread when another thread has locked the tree. This is the wrong behavior of the code and we need to remove the warning.
Fixes: 31651c607151f ("hfsplus: avoid deadlock on file truncation") Reported-by: syzbot+8c0bc9f818702ff75b76@syzkaller.appspotmail.com Closes: https://lore.kernel.org/all/00000000000057fa4605ef101c4c@google.com/ Signed-off-by: Yangtao Li frank.li@vivo.com Reviewed-by: Viacheslav Dubeyko slava@dubeyko.com Signed-off-by: Viacheslav Dubeyko slava@dubeyko.com Link: https://lore.kernel.org/r/20250529061807.2213498-1-frank.li@vivo.com Signed-off-by: Viacheslav Dubeyko slava@dubeyko.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/hfsplus/extents.c | 3 --- 1 file changed, 3 deletions(-)
diff --git a/fs/hfsplus/extents.c b/fs/hfsplus/extents.c index a6d61685ae79..b1699b3c246a 100644 --- a/fs/hfsplus/extents.c +++ b/fs/hfsplus/extents.c @@ -342,9 +342,6 @@ static int hfsplus_free_extents(struct super_block *sb, int i; int err = 0;
- /* Mapping the allocation file may lock the extent tree */ - WARN_ON(mutex_is_locked(&HFSPLUS_SB(sb)->ext_tree->tree_lock)); - hfsplus_dump_extent(extent); for (i = 0; i < 8; extent++, i++) { count = be32_to_cpu(extent->block_count);