[lvc-project] [PATCH] nilfs2: fix WARNING in nilfs_sufile_do_free

[Makar Semyonov]

Backport of 2c20b0f26694e1d40bb9b86f8eff5675e87003d1.

nilfs_sufile_do_free(), which is called when log write
fails or during GC, uses WARN_ONs to check for abnormal
status of metadata. In the former case, these WARN_ONs will
not be fired, but in the latter case they don't
"never-happen".  It is possible to trigger these by
intentionally modifying the userland GC library to release
segments that are not in the expected state. So, replace
them with warning output using the dedicated macro
nilfs_warn(). This replaces two potentially triggered
WARN_ONs with ones that use a warning output macro.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Fixes: a703018f7bbe ("nilfs2: segment usage file cleanups")
Signed-off-by: Makar Semyonov <m.semenov at tssltd.ru>
---
 fs/nilfs2/sufile.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/nilfs2/sufile.c b/fs/nilfs2/sufile.c
index dc359b56fdfa..e7f0ec06b679 100644
--- a/fs/nilfs2/sufile.c
+++ b/fs/nilfs2/sufile.c
@@ -471,10 +471,15 @@ void nilfs_sufile_do_free(struct inode *sufile, __u64 segnum,
 		kunmap_atomic(kaddr);
 		return;
 	}
-	WARN_ON(nilfs_segment_usage_error(su));
-	WARN_ON(!nilfs_segment_usage_dirty(su));
+	if (unlikely(nilfs_segment_usage_error(su)))
+		nilfs_warn(sufile->i_sb, "free segment %llu marked in error",
+			   (unsigned long long)segnum);
 
 	sudirty = nilfs_segment_usage_dirty(su);
+	if (unlikely(!sudirty))
+		nilfs_warn(sufile->i_sb, "free unallocated segment %llu",
+			   (unsigned long long)segnum);
+
 	nilfs_segment_usage_set_clean(su);
 	kunmap_atomic(kaddr);
 	mark_buffer_dirty(su_bh);
-- 
2.43.0