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From: Gao Xiang <xiang@kernel.org>
To: linux-erofs@lists.ozlabs.org, LKML <linux-kernel@vger.kernel.org>
Cc: Lasse Collin <lasse.collin@tukaani.org>,
	Chao Yu <chao@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Gao Xiang <hsiangkao@linux.alibaba.com>
Subject: [PATCH 2/7] lib/xz: Validate the value before assigning it to an enum variable
Date: Mon, 11 Oct 2021 05:31:40 +0800	[thread overview]
Message-ID: <20211010213145.17462-3-xiang@kernel.org> (raw)
In-Reply-To: <20211010213145.17462-1-xiang@kernel.org>

From: Lasse Collin <lasse.collin@tukaani.org>

This might matter, for example, if the underlying type of enum xz_check
was a signed char. In such a case the validation wouldn't have caught an
unsupported header. I don't know if this problem can occur in the kernel
on any arch but it's still good to fix it because some people might copy
the XZ code to their own projects from Linux instead of the upstream
XZ Embedded repository.

This change may increase the code size by a few bytes. An alternative
would have been to use an unsigned int instead of enum xz_check but
using an enumeration looks cleaner.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 lib/xz/xz_dec_stream.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/xz/xz_dec_stream.c b/lib/xz/xz_dec_stream.c
index fea86deaaa01..683570b93a8c 100644
--- a/lib/xz/xz_dec_stream.c
+++ b/lib/xz/xz_dec_stream.c
@@ -402,12 +402,12 @@ static enum xz_ret dec_stream_header(struct xz_dec *s)
 	 * we will accept other check types too, but then the check won't
 	 * be verified and a warning (XZ_UNSUPPORTED_CHECK) will be given.
 	 */
+	if (s->temp.buf[HEADER_MAGIC_SIZE + 1] > XZ_CHECK_MAX)
+		return XZ_OPTIONS_ERROR;
+
 	s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
 
 #ifdef XZ_DEC_ANY_CHECK
-	if (s->check_type > XZ_CHECK_MAX)
-		return XZ_OPTIONS_ERROR;
-
 	if (s->check_type > XZ_CHECK_CRC32)
 		return XZ_UNSUPPORTED_CHECK;
 #else
-- 
2.20.1


WARNING: multiple messages have this Message-ID (diff)
From: Gao Xiang <xiang@kernel.org>
To: linux-erofs@lists.ozlabs.org, LKML <linux-kernel@vger.kernel.org>
Cc: Lasse Collin <lasse.collin@tukaani.org>,
	Greg KH <gregkh@linuxfoundation.org>,
	Gao Xiang <hsiangkao@linux.alibaba.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: [PATCH 2/7] lib/xz: Validate the value before assigning it to an enum variable
Date: Mon, 11 Oct 2021 05:31:40 +0800	[thread overview]
Message-ID: <20211010213145.17462-3-xiang@kernel.org> (raw)
In-Reply-To: <20211010213145.17462-1-xiang@kernel.org>

From: Lasse Collin <lasse.collin@tukaani.org>

This might matter, for example, if the underlying type of enum xz_check
was a signed char. In such a case the validation wouldn't have caught an
unsupported header. I don't know if this problem can occur in the kernel
on any arch but it's still good to fix it because some people might copy
the XZ code to their own projects from Linux instead of the upstream
XZ Embedded repository.

This change may increase the code size by a few bytes. An alternative
would have been to use an unsigned int instead of enum xz_check but
using an enumeration looks cleaner.

Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 lib/xz/xz_dec_stream.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/lib/xz/xz_dec_stream.c b/lib/xz/xz_dec_stream.c
index fea86deaaa01..683570b93a8c 100644
--- a/lib/xz/xz_dec_stream.c
+++ b/lib/xz/xz_dec_stream.c
@@ -402,12 +402,12 @@ static enum xz_ret dec_stream_header(struct xz_dec *s)
 	 * we will accept other check types too, but then the check won't
 	 * be verified and a warning (XZ_UNSUPPORTED_CHECK) will be given.
 	 */
+	if (s->temp.buf[HEADER_MAGIC_SIZE + 1] > XZ_CHECK_MAX)
+		return XZ_OPTIONS_ERROR;
+
 	s->check_type = s->temp.buf[HEADER_MAGIC_SIZE + 1];
 
 #ifdef XZ_DEC_ANY_CHECK
-	if (s->check_type > XZ_CHECK_MAX)
-		return XZ_OPTIONS_ERROR;
-
 	if (s->check_type > XZ_CHECK_CRC32)
 		return XZ_UNSUPPORTED_CHECK;
 #else
-- 
2.20.1


  parent reply	other threads:[~2021-10-10 21:32 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-10 21:31 [PATCH 0/7] erofs: add LZMA compression support Gao Xiang
2021-10-10 21:31 ` Gao Xiang
2021-10-10 21:31 ` [PATCH 1/7] lib/xz: Avoid overlapping memcpy() with invalid input with in-place decompression Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-10 21:31 ` Gao Xiang [this message]
2021-10-10 21:31   ` [PATCH 2/7] lib/xz: Validate the value before assigning it to an enum variable Gao Xiang
2021-10-10 21:31 ` [PATCH 3/7] lib/xz: Move s->lzma.len = 0 initialization to lzma_reset() Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-10 21:31 ` [PATCH 4/7] lib/xz: Add MicroLZMA decoder Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-10 21:31 ` [PATCH 5/7] lib/xz, lib/decompress_unxz.c: Fix spelling in comments Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-10 21:31 ` [PATCH 6/7] erofs: rename some generic methods in decompressor Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-19 13:03   ` Chao Yu
2021-10-19 13:03     ` Chao Yu
2021-10-10 21:31 ` [PATCH 7/7] erofs: lzma compression support Gao Xiang
2021-10-10 21:31   ` Gao Xiang
2021-10-19 13:04   ` Chao Yu
2021-10-19 13:04     ` Chao Yu
2021-10-14  1:45 ` [PATCH 0/7] erofs: add LZMA " Gao Xiang
2021-10-14  1:45   ` Gao Xiang

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