CVE-2026-23230 – smb: client: split cached_fid bitfields to avoid shared-byte RMW races

CVE ID : CVE-2026-23230

Published : Feb. 18, 2026, 4:22 p.m. | 37 minutes ago

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

smb: client: split cached_fid bitfields to avoid shared-byte RMW races

is_open, has_lease and on_list are stored in the same bitfield byte in
struct cached_fid but are updated in different code paths that may run
concurrently. Bitfield assignments generate byte read–modify–write
operations (e.g. `orb $mask, addr` on x86_64), so updating one flag can
restore stale values of the others.

A possible interleaving is:
CPU1: load old byte (has_lease=1, on_list=1)
CPU2: clear both flags (store 0)
CPU1: RMW store (old | IS_OPEN) -> reintroduces cleared bits

To avoid this class of races, convert these flags to separate bool
fields.

Severity: 0.0 | NA

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