CVE-2025-40295

/// Technical description

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

fscrypt: fix left shift underflow when inode->i_blkbits > PAGE_SHIFT

When simulating an nvme device on qemu with both logical_block_size and

physical_block_size set to 8 KiB, an error trace appears during

partition table reading at boot time. The issue is caused by

inode->i_blkbits being larger than PAGE_SHIFT, which leads to a left

shift of -1 and triggering a UBSAN warning.

[ 2.697306] ------------[ cut here ]------------

[ 2.697309] UBSAN: shift-out-of-bounds in fs/crypto/inline_crypt.c:336:37

[ 2.697311] shift exponent -1 is negative

[ 2.697315] CPU: 3 UID: 0 PID: 274 Comm: (udev-worker) Not tainted 6.18.0-rc2+ #34 PREEMPT(voluntary)

[ 2.697317] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014

[ 2.697320] Call Trace:

[ 2.697324] <TASK>

[ 2.697325] dump_stack_lvl+0x76/0xa0

[ 2.697340] dump_stack+0x10/0x20

[ 2.69734

/// 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