Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: net/smc: stop killed, freed and out_of_sync sharing a byte The three connection state flags are single-bit bitfields, so they occupy one byte of struct smc_connection and every store to one is a read-modify-write of the other two: u8 killed : 1; u8 freed : 1; u8 out_of_sync : 1; They are not written under a common lock. smc_cdc_msg_validate() sets out_of_sync from the receive tasklet, while smc_conn_kill() sets killed from process context under lock_sock(), and the receive path does not defer to the backlog when the socket is owned -- smc_cdc_msg_recv() takes only bh_lock_sock(). Give each flag its own byte so a store no longer touches its neighbours. All readers test them as booleans and are unchanged. struct smc_connection grows by two bytes.

Affected versions

Linux: b286a0651e4404ab96cdfdcdad8a839a26b3751e through before 313f79149eb337411c64e2c247234b62ef9a3cb9 (git); b286a0651e4404ab96cdfdcdad8a839a26b3751e through before 2cb7a8d64b7e8ccdc69bbe48fe9c4eaa79c33aec (git); b286a0651e4404ab96cdfdcdad8a839a26b3751e through before db51a8658c11a82432b64999519a269c3aabb447 (git); 5.8 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.