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From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: linux-erofs@lists.ozlabs.org, Chao Yu <chao@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>, Yue Hu <huyue2@yulong.com>,
	Gao Xiang <hsiangkao@linux.alibaba.com>
Subject: [PATCH] erofs: fix buffer copy overflow of ztailpacking feature
Date: Thu, 12 May 2022 19:58:33 +0800	[thread overview]
Message-ID: <20220512115833.24175-1-hsiangkao@linux.alibaba.com> (raw)

I got some KASAN report as below:

[   46.959738] ==================================================================
[   46.960430] BUG: KASAN: use-after-free in z_erofs_shifted_transform+0x2bd/0x370
[   46.960430] Read of size 4074 at addr ffff8880300c2f8e by task fssum/188
...
[   46.960430] Call Trace:
[   46.960430]  <TASK>
[   46.960430]  dump_stack_lvl+0x41/0x5e
[   46.960430]  print_report.cold+0xb2/0x6b7
[   46.960430]  ? z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  kasan_report+0x8a/0x140
[   46.960430]  ? z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  kasan_check_range+0x14d/0x1d0
[   46.960430]  memcpy+0x20/0x60
[   46.960430]  z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  z_erofs_decompress_pcluster+0xaae/0x1080

The root cause is that the tail pcluster won't be a complete filesystem
block anymore. So if ztailpacking is used, the second part of an
uncompresed tail pcluster may not be ``rq->pageofs_out``.

Fixes: ab749badf9f4 ("erofs: support unaligned data decompression")
Fixes: cecf864d3d76 ("erofs: support inline data decompression")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/decompressor.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 0f445f7e1df8..6dca1900c733 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -320,6 +320,7 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
 		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 	const unsigned int righthalf = min_t(unsigned int, rq->outputsize,
 					     PAGE_SIZE - rq->pageofs_out);
+	const unsigned int lefthalf = rq->outputsize - righthalf;
 	unsigned char *src, *dst;
 
 	if (nrpages_out > 2) {
@@ -342,10 +343,10 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
 	if (nrpages_out == 2) {
 		DBG_BUGON(!rq->out[1]);
 		if (rq->out[1] == *rq->in) {
-			memmove(src, src + righthalf, rq->pageofs_out);
+			memmove(src, src + righthalf, lefthalf);
 		} else {
 			dst = kmap_atomic(rq->out[1]);
-			memcpy(dst, src + righthalf, rq->pageofs_out);
+			memcpy(dst, src + righthalf, lefthalf);
 			kunmap_atomic(dst);
 		}
 	}
-- 
2.24.4


WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang <hsiangkao@linux.alibaba.com>
To: linux-erofs@lists.ozlabs.org, Chao Yu <chao@kernel.org>
Cc: Gao Xiang <hsiangkao@linux.alibaba.com>,
	Yue Hu <huyue2@yulong.com>, LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH] erofs: fix buffer copy overflow of ztailpacking feature
Date: Thu, 12 May 2022 19:58:33 +0800	[thread overview]
Message-ID: <20220512115833.24175-1-hsiangkao@linux.alibaba.com> (raw)

I got some KASAN report as below:

[   46.959738] ==================================================================
[   46.960430] BUG: KASAN: use-after-free in z_erofs_shifted_transform+0x2bd/0x370
[   46.960430] Read of size 4074 at addr ffff8880300c2f8e by task fssum/188
...
[   46.960430] Call Trace:
[   46.960430]  <TASK>
[   46.960430]  dump_stack_lvl+0x41/0x5e
[   46.960430]  print_report.cold+0xb2/0x6b7
[   46.960430]  ? z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  kasan_report+0x8a/0x140
[   46.960430]  ? z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  kasan_check_range+0x14d/0x1d0
[   46.960430]  memcpy+0x20/0x60
[   46.960430]  z_erofs_shifted_transform+0x2bd/0x370
[   46.960430]  z_erofs_decompress_pcluster+0xaae/0x1080

The root cause is that the tail pcluster won't be a complete filesystem
block anymore. So if ztailpacking is used, the second part of an
uncompresed tail pcluster may not be ``rq->pageofs_out``.

Fixes: ab749badf9f4 ("erofs: support unaligned data decompression")
Fixes: cecf864d3d76 ("erofs: support inline data decompression")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/decompressor.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index 0f445f7e1df8..6dca1900c733 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -320,6 +320,7 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
 		PAGE_ALIGN(rq->pageofs_out + rq->outputsize) >> PAGE_SHIFT;
 	const unsigned int righthalf = min_t(unsigned int, rq->outputsize,
 					     PAGE_SIZE - rq->pageofs_out);
+	const unsigned int lefthalf = rq->outputsize - righthalf;
 	unsigned char *src, *dst;
 
 	if (nrpages_out > 2) {
@@ -342,10 +343,10 @@ static int z_erofs_shifted_transform(struct z_erofs_decompress_req *rq,
 	if (nrpages_out == 2) {
 		DBG_BUGON(!rq->out[1]);
 		if (rq->out[1] == *rq->in) {
-			memmove(src, src + righthalf, rq->pageofs_out);
+			memmove(src, src + righthalf, lefthalf);
 		} else {
 			dst = kmap_atomic(rq->out[1]);
-			memcpy(dst, src + righthalf, rq->pageofs_out);
+			memcpy(dst, src + righthalf, lefthalf);
 			kunmap_atomic(dst);
 		}
 	}
-- 
2.24.4


             reply	other threads:[~2022-05-12 11:58 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-12 11:58 Gao Xiang [this message]
2022-05-12 11:58 ` [PATCH] erofs: fix buffer copy overflow of ztailpacking feature Gao Xiang
2022-05-13  6:14 ` Yue Hu
2022-05-13  6:14   ` Yue Hu
2022-05-17 15:10 ` Chao Yu
2022-05-17 15:10   ` Chao Yu
2022-05-18  6:49   ` Gao Xiang
2022-05-18  6:49     ` Gao Xiang

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