This issue was discovered during a code audit. After cancel_delayed_work_sync() is called from tls_sk_proto_close(), tx_work_handler() can still be scheduled from paths such as the Delayed ACK handler or ksoftirqd. As a result, the tx_work_handler() worker may dereference a freed TLS object. The following is a simple race scenario: cpu0 cpu1 tls_sk_proto_close() tls_sw_cancel_work_tx() tls_write_space() tls_sw_write_space() if (!test_and_set_bit(BIT_TX_SCHEDULED, &tx_ctx->tx_bitmask)) set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask); cancel_delayed_work_sync(&ctx->tx_work.work); schedule_delayed_work(&tx_ctx->tx_work.work, 0); To prevent this race condition, cancel_delayed_work_sync() is replaced with disable_delayed_work_sync(). Fixes: f87e62d45e51 ("net/tls: remove close callback sock unlock/lock around TX work flush") Signed-off-by: Hyunwoo Kim --- Changes in v2: - Shorten the patch subject - Target the net tree - Add the bug discovery background and the race scenario to the commit message - v1: https://lore.kernel.org/all/aZLotq3aZY0b-dI8@v4bel/ --- net/tls/tls_sw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index 9937d4c810f2..b1fa62de9dab 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -2533,7 +2533,7 @@ void tls_sw_cancel_work_tx(struct tls_context *tls_ctx) set_bit(BIT_TX_CLOSING, &ctx->tx_bitmask); set_bit(BIT_TX_SCHEDULED, &ctx->tx_bitmask); - cancel_delayed_work_sync(&ctx->tx_work.work); + disable_delayed_work_sync(&ctx->tx_work.work); } void tls_sw_release_resources_tx(struct sock *sk) -- 2.43.0