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.