From: Damien Le Moal damien.lemoal@wdc.com
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/20210820070255.682775-2-damien.lemoal@wdc.com Signed-off-by: Damien Le Moal damien.lemoal@wdc.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Vasiliy Kovalev kovalev@altlinux.org --- Backport to fix CVE-2021-47182 Link: https://www.cve.org/CVERecord/?id=CVE-2021-47182 --- 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 fb48d47e9183e..06838cf5300d0 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -2073,7 +2073,7 @@ 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. @@ -2108,18 +2108,18 @@ 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; @@ -2144,8 +2144,14 @@ 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; } @@ -2163,12 +2169,11 @@ 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];