CVE-2026-31412

About vulnerability

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

usb: gadget: f_mass_storage: Fix potential integer overflow in check_command_size_in_blocks()

The check_command_size_in_blocks() function calculates the data size in bytes by left shifting common->data_size_from_cmnd by the block size (common->curlun->blkbits). However, it does not validate whether this shift operation will cause an integer overflow.

Initially, the block size is set up in fsg_lun_open() , and the common->data_size_from_cmnd is set up in do_scsi_command(). During initialization, there is no integer overflow check for the interaction between two variables.

So if a malicious USB host sends a SCSI READ or WRITE command requesting a large amount of data (common->data_size_from_cmnd), the left shift operation can wrap around. This results in a truncated data size, which can bypass boundary checks and potentially lead to memory corruption or out-of-bounds accesses.

Fix this by using the check_shl_overflow() macro to safely perform the shift and catch any overflows.

Affected product:

AlmaLinux 9.2 ESU , CentOS 7 ELS , CentOS 8.4 ELS , CentOS 8.5 ELS , CentOS Stream 8 ELS , CloudLinux 7 ELS , Oracle Linux 7 ELS , RHEL 7 ELS , TuxCare 9.6 ESU , Ubuntu 16.04 ELS , Ubuntu 18.04 ELS , Ubuntu 20.04 ELS

Affected packages:

kernel @ 4.18.0 (+13 more)

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

usb: gadget: f_mass_storage: Fix potential integer overflow in check_command_size_in_blocks()

The check_command_size_in_blocks() function calculates the data size in bytes by left shifting common->data_size_from_cmnd by the block size (common->curlun->blkbits). However, it does not validate whether this shift operation will cause an integer overflow.

Initially, the block size is set up in fsg_lun_open() , and the common->data_size_from_cmnd is set up in do_scsi_command(). During initialization, there is no integer overflow check for the interaction between two variables.

So if a malicious USB host sends a SCSI READ or WRITE command requesting a large amount of data (common->data_size_from_cmnd), the left shift operation can wrap around. This results in a truncated data size, which can bypass boundary checks and potentially lead to memory corruption or out-of-bounds accesses.

Fix this by using the check_shl_overflow() macro to safely perform the shift and catch any overflows.