net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks()

Summary

In the Linux kernel, the following vulnerability has been resolved: net/rds: acquire RDS_IN_XMIT in rds_tcp_reset_callbacks() rds_tcp_reset_callbacks() quiesces the transmit path by setting the path state to RDS_CONN_RESETTING and then waiting for RDS_IN_XMIT to be sampled clear before swapping the underlying socket and calling rds_send_path_reset(). Sampling the bit clear is not the same as owning it: rds_send_xmit() can re-acquire RDS_IN_XMIT right after the wait_event() returns. Its state recheck after taking the lock is a store-buffering pattern (the resetter writes the state and reads the bit, the sender writes the bit and reads the state) and acquire_in_xmit() is only an acquire operation, so on weakly ordered architectures both sides can miss each other's write and the transmit path then runs concurrently with rds_send_path_reset() rewriting cp_xmit_* state - which is exactly what the comment above rds_send_path_reset() tells its callers to prevent. Take the lock instead, hold it across the socket swap and rds_send_path_reset(), and release it with a wake-up at the end. The lock-ordering constraint documented above the wait still holds: the lock is acquired before lock_sock(), so a sender inside tcp_sendmsg() can never be waited on while we hold the socket lock. Two details of the old code go away with the same change: • t_sock is now read only after the lock is acquired. The old code cached it before waiting; the teardown in rds_conn_shutdown() releases that socket and clears t_sock, so a pointer cached before the wait can be stale by the time the accept path resumes. Reading it under RDS_IN_XMIT is what makes the exclusion complete once the teardown owns the same lock, which the next patch arranges; until then the teardown still only samples the bit, and the two paths remain as exposed to each other as they are today. • The old !osock early path called rds_send_path_reset() with no serialization at all. It now runs under the lock like the normal path. The conditional RDS_CONN_RESETTING transition of the previous patch happens before the socket check either way: a path found without a socket is either still connecting (its reconnect worker blocked on t_conn_path_lock) and legitimately goes RESETTING -> UP on the new socket, or it has been torn down meanwhile and is dropped. The in-function comment describing the old wait-based quiesce is rewritten to describe the lock-based one, and the stale block comment above the function (which still described a return value and an incomplete list of t_sock writers) is refreshed to name all four writers - the connect, accept, teardown and swap paths - and what serializes each of them.

Timeline

1. Sep 25, 2026, 10:24 AM UTCCVE published
2. Oct 19, 2026, 9:13 AM UTCRecord last updated

Affected versions

• Linux Linux

  From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in 670af4e4a4de5e6bb5daee3838485571a0caa5fa; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in 830a2e21b200c6b6fdccc63dd3f23932bf7a894b; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in a05790cb4ff03f797d76906990b148d83f63e7a3; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in d184e6dd4b8f3c20c018595fd09795a66b46c8ef; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in d625112564c3e980e02504270222b49b82690cee; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in 8e4c3b7844c906c7097b4cfedd9dd1f48c9a6a92; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in 062d9e008c67289e8e1b221ecdd8f9d60566d012; From 335b48d980f631fbc5b233cbb3625ac0c86d67cb · fixed in 02c5f9dc2efd823e061954d564ce00bacd1bebeb

• Linux Linux

  4.7

• KernelLinux

  From 4.7.0 · fixed in 5.10.271; From 5.11.0 · fixed in 5.15.222; From 5.16.0 · fixed in 6.1.189; From 6.2.0 · fixed in 6.6.158; From 6.7.0 · fixed in 6.12.111; From 6.13.0 · fixed in 6.18.53; From 6.19.0 · fixed in 7.2.7

References 8