CVE-2021-47182

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

scsi: core: Fix scsi_mode_sense() buffer length handling

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.

Furthermor

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References