scsi: core: Backport fixes for CVE-2021-47182

PATCH New Vasiliy Kovalev 2 participants 3 messages Nov 22, 2024 Stable branch

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Vasiliy Kovalev

author

2024-11-22 19:07 UTC #0 lore raw

PATCH 1/1 scsi: core: Backport fixes for CVE-2021-47182

The patch titled "scsi: core: Fix scsi_mode_sense() buffer length handling" addresses CVE-2021-47182, fixing the following issues in scsi_mode_sense() buffer length handling:

1. Incorrect handling of the allocation length field in the MODE SENSE(10) command, causing truncation of buffer lengths larger than 255 bytes.

2. Memory corruption when handling small buffer lengths due to lack of proper validation.

Original patch submission:
https://lore.kernel.org/all/[email protected]/

CVE announcement in linux-cve-announce:
https://lore.kernel.org/linux-cve-announce/2024041032-CVE-2021-47182-377e@gregkh/
Fixed versions:
- Fixed in 5.15.5 with commit e15de347faf4
- Fixed in 5.16 with commit 17b49bcbf835

Official CVE entry:
https://cve.org/CVERecord/?id=CVE-2021-47182

[PATCH 5.10.y] scsi: core: Fix scsi_mode_sense() buffer length handling

Vasiliy Kovalev

author

2024-11-22 19:07 UTC #1 lore raw

PATCH 1/1 scsi: core: Fix scsi_mode_sense() buffer length handling

From: Damien Le Moal <[email protected]>

commit 17b49bcbf8351d3dbe57204468ac34f033ed60bc upstream.

Several problems exist with scsi_mode_sense() buffer length handling:

1) The allocation length field of the MODE SENSE(10) command is 16-bits, occupying bytes 7 and 8 of the CDB. With this command, access to mode pages larger than 255 bytes is thus possible. However, the CDB allocation length field is set by assigning len to byte 8 only, thus truncating buffer length larger than 255.

2) If scsi_mode_sense() is called with len smaller than 8 with sdev->use_10_for_ms set, or smaller than 4 otherwise, the buffer length is increased to 8 and 4 respectively, and the buffer is zero filled with these increased values, thus corrupting the memory following the buffer.

Fix these 2 problems by using put_unaligned_be16() to set the allocation length field of MODE SENSE(10) CDB and by returning an error when len is too small.

Furthermore, if len is larger than 255B, always try MODE SENSE(10) first, even if the device driver did not set sdev->use_10_for_ms. In case of invalid opcode error for MODE SENSE(10), access to mode pages larger than 255 bytes are not retried using MODE SENSE(6). To avoid buffer length overflows for the MODE_SENSE(10) case, check that len is smaller than 65535 bytes.

While at it, also fix the folowing:

* Use get_unaligned_be16() to retrieve the mode data length and block descriptor length fields of the mode sense reply header instead of using an open coded calculation.

* Fix the kdoc dbd argument explanation: the DBD bit stands for Disable Block Descriptor, which is the opposite of what the dbd argument description was.

Link https://lore.kernel.org/r/[email protected] open here

Signed-off-by Damien Le Moal <[email protected]>

Signed-off-by Martin K. Petersen <[email protected]>

Signed-off-by Vasiliy Kovalev <[email protected]>

---
 drivers/scsi/scsi_lib.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

drivers/scsi/scsi_lib.c +15 ~~-10~~

index 64ae7bc2de604..0a9db3464fd48 100644
@@ -2068,7 +2068,7 @@ EXPORT_SYMBOL_GPL(scsi_mode_select);
 /**
  *	scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
  *	@sdev:	SCSI device to be queried
- *	@dbd:	set if mode sense will allow block descriptors to be returned
+ *	@dbd:	set to prevent mode sense from returning block descriptors
  *	@modepage: mode page being requested
  *	@buffer: request buffer (may not be smaller than eight bytes)
  *	@len:	length of request buffer.

@@ -2103,18 +2103,18 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 		sshdr = &my_sshdr;
 
  retry:
-	use_10_for_ms = sdev->use_10_for_ms;
+	use_10_for_ms = sdev->use_10_for_ms || len > 255;
 
 	if (use_10_for_ms) {
-		if (len < 8)
-			len = 8;
+		if (len < 8 || len > 65535)
+			return -EINVAL;
 
 		cmd[0] = MODE_SENSE_10;
-		cmd[8] = len;
+		put_unaligned_be16(len, &cmd[7]);
 		header_length = 8;
 	} else {
 		if (len < 4)
-			len = 4;
+			return -EINVAL;
 
 		cmd[0] = MODE_SENSE;
 		cmd[4] = len;

@@ -2139,8 +2139,14 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
 			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
 				/*
-				 * Invalid command operation code
+				 * Invalid command operation code: retry using
+				 * MODE SENSE(6) if this was a MODE SENSE(10)
+				 * request, except if the request mode page is
+				 * too large for MODE SENSE single byte
+				 * allocation length field.
 				 */
+				if (len > 255)
+					return -EIO;
 				sdev->use_10_for_ms = 0;
 				goto retry;
 			}

@@ -2158,12 +2164,11 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
 			data->longlba = 0;
 			data->block_descriptor_length = 0;
 		} else if (use_10_for_ms) {
-			data->length = buffer[0]*256 + buffer[1] + 2;
+			data->length = get_unaligned_be16(&buffer[0]) + 2;
 			data->medium_type = buffer[2];
 			data->device_specific = buffer[3];
 			data->longlba = buffer[4] & 0x01;
-			data->block_descriptor_length = buffer[6]*256
-				+ buffer[7];
+			data->block_descriptor_length = get_unaligned_be16(&buffer[6]);
 		} else {
 			data->length = buffer[0] + 1;
 			data->medium_type = buffer[1];

Signature · 1 line

2.33.8

Sasha Levin

maintainer

2024-11-22 19:39 UTC #2 lore raw

Re: [PATCH 5.10.y] scsi: core: Fix scsi_mode_sense() buffer length handling

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 17b49bcbf8351d3dbe57204468ac34f033ed60bc

WARNING: Author mismatch between patch and upstream commit:
Backport author: Vasiliy Kovalev <[email protected]> Commit author: Damien Le Moal <[email protected]>

Note: The patch differs from the upstream commit:
---

tmp/tmp.ZvzLslfZma renamed from - +30 ~~-25~~

@@ -1,3 +1,5 @@
+commit 17b49bcbf8351d3dbe57204468ac34f033ed60bc upstream.
+
 Several problems exist with scsi_mode_sense() buffer length handling:
 
  1) The allocation length field of the MODE SENSE(10) command is 16-bits,

@@ -36,15 +38,16 @@
 Link: https://lore.kernel.org/r/[email protected]
 Signed-off-by: Damien Le Moal <[email protected]>
 Signed-off-by: Martin K. Petersen <[email protected]>
+Signed-off-by: Vasiliy Kovalev <[email protected]>
 ---
  drivers/scsi/scsi_lib.c | 25 +++++++++++++++----------
  1 file changed, 15 insertions(+), 10 deletions(-)
 
 diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
-index 572673873ddf8..701d8e8480f22 100644
+index 64ae7bc2de604..0a9db3464fd48 100644
 --- a/drivers/scsi/scsi_lib.c
 +++ b/drivers/scsi/scsi_lib.c
-@@ -2075,7 +2075,7 @@ EXPORT_SYMBOL_GPL(scsi_mode_select);
+@@ -2068,7 +2068,7 @@ EXPORT_SYMBOL_GPL(scsi_mode_select);
  /**
   *	scsi_mode_sense - issue a mode sense, falling back from 10 to six bytes if necessary.
   *	@sdev:	SCSI device to be queried

@@ -53,7 +56,7 @@
   *	@modepage: mode page being requested
   *	@buffer: request buffer (may not be smaller than eight bytes)
   *	@len:	length of request buffer.
-@@ -2110,18 +2110,18 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
+@@ -2103,18 +2103,18 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
  		sshdr = &my_sshdr;
  
   retry:

@@ -77,7 +80,7 @@
  
  		cmd[0] = MODE_SENSE;
  		cmd[4] = len;
-@@ -2145,9 +2145,15 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
+@@ -2139,8 +2139,14 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
  			if ((sshdr->sense_key == ILLEGAL_REQUEST) &&
  			    (sshdr->asc == 0x20) && (sshdr->ascq == 0)) {
  				/*

@@ -88,24 +91,26 @@
 +				 * too large for MODE SENSE single byte
 +				 * allocation length field.
  				 */
- 				if (use_10_for_ms) {
-+					if (len > 255)
-+						return -EIO;
- 					sdev->use_10_for_ms = 0;
- 					goto retry;
- 				}
-@@ -2171,12 +2177,11 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
- 		data->longlba = 0;
- 		data->block_descriptor_length = 0;
- 	} else if (use_10_for_ms) {
--		data->length = buffer[0]*256 + buffer[1] + 2;
-+		data->length = get_unaligned_be16(&buffer[0]) + 2;
- 		data->medium_type = buffer[2];
- 		data->device_specific = buffer[3];
- 		data->longlba = buffer[4] & 0x01;
--		data->block_descriptor_length = buffer[6]*256
--			+ buffer[7];
-+		data->block_descriptor_length = get_unaligned_be16(&buffer[6]);
- 	} else {
- 		data->length = buffer[0] + 1;
- 		data->medium_type = buffer[1];
++				if (len > 255)
++					return -EIO;
+ 				sdev->use_10_for_ms = 0;
+ 				goto retry;
+ 			}
+@@ -2158,12 +2164,11 @@ scsi_mode_sense(struct scsi_device *sdev, int dbd, int modepage,
+ 			data->longlba = 0;
+ 			data->block_descriptor_length = 0;
+ 		} else if (use_10_for_ms) {
+-			data->length = buffer[0]*256 + buffer[1] + 2;
++			data->length = get_unaligned_be16(&buffer[0]) + 2;
+ 			data->medium_type = buffer[2];
+ 			data->device_specific = buffer[3];
+ 			data->longlba = buffer[4] & 0x01;
+-			data->block_descriptor_length = buffer[6]*256
+-				+ buffer[7];
++			data->block_descriptor_length = get_unaligned_be16(&buffer[6]);
+ 		} else {
+ 			data->length = buffer[0] + 1;
+ 			data->medium_type = buffer[1];
+-- 
+2.33.8
+

---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.10.y       |  Success    |  Success   |