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ocfs2: fix out-of-bounds write in ocfs2_remove_refcount_extent

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[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: 2f26f58df0 ("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>
This commit is contained in:
Ian Bridges 2026-06-01 13:44:33 -05:00 committed by Andrew Morton
parent 57dcfd9049
commit 1ec3cca2d8
1 changed files with 7 additions and 2 deletions
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9
fs/ocfs2/refcounttree.c
View File

@ -2131,10 +2131,15 @@ static int ocfs2_remove_refcount_extent(handle_t *handle,
rb->rf_flags = 0;
rb->rf_parent = 0;
rb->rf_cpos = 0;
memset(&rb->rf_records, 0, sb->s_blocksize -
offsetof(struct ocfs2_refcount_block, rf_records));
rb->rf_records.rl_used = 0;
rb->rf_records.rl_reserved2 = 0;
rb->rf_records.rl_reserved1 = 0;
/* rl_count determines the memset size and fortify object size. */
rb->rf_records.rl_count =
cpu_to_le16(ocfs2_refcount_recs_per_rb(sb));
memset(rb->rf_records.rl_recs, 0,
le16_to_cpu(rb->rf_records.rl_count) *
sizeof(*rb->rf_records.rl_recs));
}
ocfs2_journal_dirty(handle, ref_root_bh);