[lvc-project] [PATCH v2] ocfs2: fix __counted_by_le() usage in ocfs2_expand_inline_dx_root()

[Dmitry Antipov]

After annotating 'l_recs[]' VLA member of 'struct ocfs2_extent_list'
with '__counted_by_le(l_count)', 'l_count' should be initialized
before touching 'l_recs[]' with 'memset()' to avoid false positives
from buffer overflow guards when CONFIG_UBSAN_BOUNDS is enabled.

Fixes: aa545adbe491 ("ocfs2: annotate flexible array members with __counted_by_le()")
Signed-off-by: Dmitry Antipov <dmantipov at yandex.ru>
---
v2: adjust 'memset()' call to clear 'l_recs[]' of 'dr_list' only
    and initialize the rest of the members explicitly (Heming Zhao)

note: since the commit in subject is not merged to upstream yet, Fixes: reference is taken from
https://web.git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git/commit/?h=mm-nonmm-unstable&id=aa545adbe491
---
 fs/ocfs2/dir.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/fs/ocfs2/dir.c b/fs/ocfs2/dir.c
index 8c9c4825f984..48b092bc83d4 100644
--- a/fs/ocfs2/dir.c
+++ b/fs/ocfs2/dir.c
@@ -4104,10 +4104,15 @@ static int ocfs2_expand_inline_dx_root(struct inode *dir,
 	}
 
 	dx_root->dr_flags &= ~OCFS2_DX_FLAG_INLINE;
-	memset(&dx_root->dr_list, 0, osb->sb->s_blocksize -
-	       offsetof(struct ocfs2_dx_root_block, dr_list));
+
+	dx_root->dr_list.l_tree_depth = 0;
 	dx_root->dr_list.l_count =
 		cpu_to_le16(ocfs2_extent_recs_per_dx_root(osb->sb));
+	dx_root->dr_list.l_next_free_rec = 0;
+	memset(&dx_root->dr_list.l_recs, 0,
+	       osb->sb->s_blocksize -
+	       (offsetof(struct ocfs2_dx_root_block, dr_list) +
+		offsetof(struct ocfs2_extent_list, l_recs)));
 
 	/* This should never fail considering we start with an empty
 	 * dx_root. */
-- 
2.51.0