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

Summary

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.

Timeline

1. Feb 18, 2026, 2:53 PM UTCCVE published
2. Oct 16, 2026, 3:06 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: total

3. Oct 19, 2026, 6:35 PM UTCRecord last updated

Affected versions

• Linux Linux

  From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in 569fecc56bfe4df66f05734d67daef887746656b; From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in 4386f6af8aaedd0c5ad6f659b40cadcc8f423828; From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in 3eaa22d688311c708b73f3c68bc6d0c8e3f0f77a; From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in c4b9edd55987384a1f201d3d07ff71e448d79c1b; From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in 4cfa4c37dcbcfd70866e856200ed8a2894cac578; From ebe98f1447bbccf8228335c62d86af02a0ed23f7 · fixed in ec306600d5ba7148c9dbf8f5a8f1f5c1a044a241

• Linux Linux

  6.1

• KernelLinux

  From 6.1.0 · fixed in 6.1.164; From 6.2.0 · fixed in 6.6.125; From 6.7.0 · fixed in 6.12.72; From 6.13.0 · fixed in 6.18.11; From 6.19.0 · fixed in 6.19.1

References 6