linux-kernel - [PATCH] ntfs: change check order in ntfs_attr

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Message-Id: <20220826123257.3826-1-yin31149@gmail.com>
Date:   Fri, 26 Aug 2022 20:32:57 +0800
From:   Hawkins Jiawei <yin31149@...il.com>
To:     yin31149@...il.com, Anton Altaparmakov <anton@...era.com>
Cc:     akpm@...ux-foundation.org, chenxiaosong2@...wei.com,
        linux-kernel@...r.kernel.org, linux-ntfs-dev@...ts.sourceforge.net,
        syzbot+5f8dcabe4a3b2c51c607@...kaller.appspotmail.com,
        syzkaller-bugs@...glegroups.com
Subject: [PATCH] ntfs: change check order in ntfs_attr_find

> 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.

Sorry for wrong command.
#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

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