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From: Hawkins Jiawei <yin31149@gmail.com>
To: syzbot+5f8dcabe4a3b2c51c607@syzkaller.appspotmail.com,
	Anton Altaparmakov <anton@tuxera.com>
Cc: akpm@linux-foundation.org, chenxiaosong2@huawei.com,
	linux-kernel@vger.kernel.org,
	linux-ntfs-dev@lists.sourceforge.net,
	syzkaller-bugs@googlegroups.com, yin31149@gmail.com
Subject: [PATCH] ntfs: change check order in ntfs_attr_find
Date: Fri, 26 Aug 2022 20:27:34 +0800	[thread overview]
Message-ID: <20220826122735.2690-1-yin31149@gmail.com> (raw)
In-Reply-To: <0000000000006886bd05e714ec18@google.com>

syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

Looks like it is improper check order that causes this bug.

Signed-off-by: Hawkins Jiawei <yin31149@gmail.com>
---
 fs/ntfs/attrib.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs/attrib.c b/fs/ntfs/attrib.c
index 52615e6090e1..6480cd2d371d 100644
--- a/fs/ntfs/attrib.c
+++ b/fs/ntfs/attrib.c
@@ -594,10 +594,11 @@ static int ntfs_attr_find(const ATTR_TYPE type, const ntfschar *name,
 	for (;;	a = (ATTR_RECORD*)((u8*)a + le32_to_cpu(a->length))) {
 		u8 *mrec_end = (u8 *)ctx->mrec +
 		               le32_to_cpu(ctx->mrec->bytes_allocated);
+		if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end)
+			break;
 		u8 *name_end = (u8 *)a + le16_to_cpu(a->name_offset) +
 			       a->name_length * sizeof(ntfschar);
-		if ((u8*)a < (u8*)ctx->mrec || (u8*)a > mrec_end ||
-		    name_end > mrec_end)
+		if (name_end > mrec_end)
 			break;
 		ctx->attr = a;
 		if (unlikely(le32_to_cpu(a->type) > le32_to_cpu(type) ||
-- 
2.25.1


  parent reply	other threads:[~2022-08-26 12:27 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-08-25 18:25 [syzbot] KASAN: use-after-free Read in ntfs_attr_find syzbot
2022-08-25 18:32 ` Siddh Raman Pant
2022-08-25 18:34   ` Siddh Raman Pant
2022-08-26 12:27 ` Hawkins Jiawei [this message]
2022-08-26 12:32   ` [PATCH] ntfs: change check order " Hawkins Jiawei
2022-08-26 14:16     ` [syzbot] KASAN: use-after-free Read " syzbot
2022-08-26 15:15     ` [PATCH] ntfs: change check order " Dan Carpenter
2022-08-26 15:42       ` Hawkins Jiawei
2022-08-26 15:54         ` Hawkins Jiawei
2022-08-27  6:42         ` Dan Carpenter
2022-08-27  9:02           ` Hawkins Jiawei
2022-08-27 10:58             ` Dan Carpenter
2022-08-28 16:15               ` Hawkins Jiawei
2022-08-27  2:42     ` Andrew Morton
2022-08-27  8:38       ` Hawkins Jiawei
2022-08-27  1:28   ` chenxiaosong (A)
2022-08-27  7:51     ` Hawkins Jiawei
2022-08-27 14:49       ` Hawkins Jiawei
2022-08-29  9:51         ` Dan Carpenter

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