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From: Tadeusz Struk <tadeusz.struk@linaro.org>
To: linkinjeon@kernel.org
Cc: Tadeusz Struk <tadeusz.struk@linaro.org>,
	Sungjong Seo <sj1557.seo@samsung.com>,
	linux-fsdevel@vger.kernel.org, stable@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	syzbot+a4087e40b9c13aad7892@syzkaller.appspotmail.com
Subject: [PATCH v2 2/2] exfat: check if cluster num is valid
Date: Wed, 11 May 2022 11:59:09 -0700	[thread overview]
Message-ID: <20220511185909.175110-2-tadeusz.struk@linaro.org> (raw)
In-Reply-To: <20220511185909.175110-1-tadeusz.struk@linaro.org>

Syzbot reported slab-out-of-bounds read in exfat_clear_bitmap.
This was triggered by reproducer calling truncute with size 0,
which causes the following trace:

BUG: KASAN: slab-out-of-bounds in exfat_clear_bitmap+0x147/0x490 fs/exfat/balloc.c:174
Read of size 8 at addr ffff888115aa9508 by task syz-executor251/365

Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack_lvl+0x1e2/0x24b lib/dump_stack.c:118
 print_address_description+0x81/0x3c0 mm/kasan/report.c:233
 __kasan_report mm/kasan/report.c:419 [inline]
 kasan_report+0x1a4/0x1f0 mm/kasan/report.c:436
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report_generic.c:309
 exfat_clear_bitmap+0x147/0x490 fs/exfat/balloc.c:174
 exfat_free_cluster+0x25a/0x4a0 fs/exfat/fatent.c:181
 __exfat_truncate+0x99e/0xe00 fs/exfat/file.c:217
 exfat_truncate+0x11b/0x4f0 fs/exfat/file.c:243
 exfat_setattr+0xa03/0xd40 fs/exfat/file.c:339
 notify_change+0xb76/0xe10 fs/attr.c:336
 do_truncate+0x1ea/0x2d0 fs/open.c:65

Add checks to validate if cluster number is within valid range in
exfat_clear_bitmap() and exfat_set_bitmap()

Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Sungjong Seo <sj1557.seo@samsung.com>
Cc: linux-fsdevel@vger.kernel.org
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

Link: https://syzkaller.appspot.com/bug?id=50381fc73821ecae743b8cf24b4c9a04776f767c
Reported-by: syzbot+a4087e40b9c13aad7892@syzkaller.appspotmail.com
Fixes: 1e49a94cf707 ("exfat: add bitmap operations")
Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
---
v2:
 - Use is_valid_cluster() helper to validate clu
---
 fs/exfat/balloc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/fs/exfat/balloc.c b/fs/exfat/balloc.c
index 03f142307174..92f5b5b5a0d0 100644
--- a/fs/exfat/balloc.c
+++ b/fs/exfat/balloc.c
@@ -149,6 +149,9 @@ int exfat_set_bitmap(struct inode *inode, unsigned int clu, bool sync)
 	struct exfat_sb_info *sbi = EXFAT_SB(sb);
 
 	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
+	if (!is_valid_cluster(sbi, clu))
+		return -EINVAL;
+
 	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
 	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
 	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
@@ -167,6 +170,9 @@ void exfat_clear_bitmap(struct inode *inode, unsigned int clu, bool sync)
 	struct exfat_mount_options *opts = &sbi->options;
 
 	WARN_ON(clu < EXFAT_FIRST_CLUSTER);
+	if (!is_valid_cluster(sbi, clu))
+		return;
+
 	ent_idx = CLUSTER_TO_BITMAP_ENT(clu);
 	i = BITMAP_OFFSET_SECTOR_INDEX(sb, ent_idx);
 	b = BITMAP_OFFSET_BIT_IN_SECTOR(sb, ent_idx);
-- 
2.36.1


  reply	other threads:[~2022-05-11 18:59 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20220511185940epcas1p3c5eb0603b969fe2753b4f16f6f8842a7@epcas1p3.samsung.com>
2022-05-11 18:59 ` [PATCH v2 1/2] exfat: move is_valid_cluster to a common header Tadeusz Struk
2022-05-11 18:59   ` Tadeusz Struk [this message]
2022-05-15 14:52     ` [PATCH v2 2/2] exfat: check if cluster num is valid Sungjong Seo
2022-05-16 14:51       ` Tadeusz Struk
2022-05-16 23:31         ` Namjae Jeon
2022-05-16 23:38           ` Tadeusz Struk
2022-05-15 14:38   ` [PATCH v2 1/2] exfat: move is_valid_cluster to a common header Sungjong Seo

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