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

Affected Software

References

• https://git.kernel.org/stable/c/1b495fa0d4927c88d88bf346bf311f2e26e860ed
• https://git.kernel.org/stable/c/65358d89dc9f1c25d9364b2b3ef0f3b47717f9ed
• https://git.kernel.org/stable/c/8eff7cd4817e14dbe3b9952cce55ef52d1d38940
• https://git.kernel.org/stable/c/9f32f38265014fac7f5dc9490fb01a638ce6e121
• https://git.kernel.org/stable/c/adc8b9c30d716c362646edb45662aa1c641a154a
• https://git.kernel.org/stable/c/e99f2df433c63c86c93de1e5f08f16e404388756