CVE-2026-97991

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

vdpa_sim_blk: reject out-of-range sector starts

vdpasim_blk_check_range() logs an invalid start sector but continues

validating the request. The subsequent unsigned capacity subtraction can

underflow and let an out-of-range buffer offset reach the data path.

The invalid offset is used by three request paths. VIRTIO_BLK_T_OUT

copies guest data to blk->buffer + offset through

vringh_iov_pull_iotlb(), causing an out-of-bounds write in

_copy_from_iter() or memcpy(). VIRTIO_BLK_T_IN copies from

blk->buffer + offset to the guest through vringh_iov_push_iotlb(),

causing an out-of-bounds read in _copy_to_iter().

VIRTIO_BLK_T_WRITE_ZEROES passes blk->buffer + offset to memset(),

causing an out-of-bounds write.

Reject starts at or beyond the capacity before the subtraction. Treat the

capacity boundary as invalid because the IN and OUT paths round byte counts

down to sectors for validation but later copy the original byte counts. A

sub-sector request at the capacity boundary would otherwise still access

past the end of the buffer.

I found this bug myself, though the patch was written with AI assistance.