ocfs2: fix out-of-bounds write in ocfs2_remove_refcount_extent

[BUG]
Unlinking a refcounted file whose refcount tree has leaf blocks
triggers a fortify panic due to an out-of-bounds write.

[CAUSE]
When the last leaf block is removed from a refcount tree,
ocfs2_remove_refcount_extent() converts the root back to leaf mode
with a bulk memset on &rb->rf_records. rf_records sits in an anonymous
union with rf_list. rf_list.l_tree_depth aliases rf_records.rl_count,
and is 0 for a single-level tree. With rl_count equal to 0, the memset
writes past the 16-byte declared size of rf_records, which the fortify
checker catches.

[FIX]
Replace the bulk memset on &rb->rf_records with a correctly-bounded
memset on rl_recs[] alone, after setting rl_count to the correct value.

Link: https://lore.kernel.org/ah3TESOsEO9j_JLU@dev
Fixes: 2f26f58df041 ("ocfs2: annotate flexible array members with __counted_by_le()")
Signed-off-by: Ian Bridges <icb@fastmail.org>
Reported-by: syzbot+3ef989aae096b30f1663@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=3ef989aae096b30f1663
Reviewed-by: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Changwei Ge <gechangwei@live.cn>
Cc: Jun Piao <piaojun@huawei.com>
Cc: Heming Zhao <heming.zhao@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

0 files changed, 0 insertions, 0 deletions