CVE-2026-64449

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

staging: vme_user: bound slave read/write to the kern_buf size

The SLAVE-path helpers buffer_to_user() and buffer_from_user() copy

'count' bytes into/out of the fixed-size kern_buf (size_buf ==

PCI_BUF_SIZE == 0x20000, 128 KiB) using *ppos as the offset, without

bounding *ppos + count against size_buf.

vme_user_write()/vme_user_read() only clamp count to the VME window size

(image_size = vme_get_size(resource)), which VME_SET_SLAVE sets from the

user-supplied slave.size -- validated against the VME address space (up

to VME_A32_MAX = 4 GiB), not against PCI_BUF_SIZE. When the window

exceeds 128 KiB, a write()/read() copies past the kern_buf allocation.

Clamp count against size_buf in both helpers, with an early return when

*ppos is already at/after the buffer end. *ppos is >= 0 here (the caller

rejects negative offsets), so size_buf - *ppos cannot wrap. This mirrors

the existing clamp in the MASTER-path helpers resource_to_user() /

resource_from_user(), and matches the read()/write() convention of a

short transfer at end-of-buffer.

Found by static analysis (CodeQL taint tracking + CBMC bounded model

checking) and confirmed dynamically under KASAN with the vme_fake bridge:

BUG: KASAN: slab-out-of-bounds in _copy_from_user+0x2d/0x80

Write of size 262144 at addr ffff888004100000 by task trigger/68

_copy_from_user+0x2d/0x80

vme_user_write+0x13e/0x240 [vme_user]

vfs_write+0x1b8/0x7a0

ksys_write+0xb8/0x150