From: Chuck Lever Per ISO/IEC 9899:2011 section 6.2.4p2, a pointer value becomes indeterminate when the object it points to reaches the end of its lifetime; Annex J.2 classifies the use of such a value as undefined behavior. In tls_sw_read_sock(), consume_skb(skb) in the fully-consumed path frees the skb, but the "do { } while (skb)" loop condition then evaluates that freed pointer. Although the value is never dereferenced -- the loop either continues and overwrites skb, or exits -- any future change that adds a dereference between consume_skb() and the loop condition would produce a silent use-after-free. Fixes: 662fbcec32f4 ("net/tls: implement ->read_sock()") Reviewed-by: Hannes Reinecke Reviewed-by: Alistair Francis Signed-off-by: Chuck Lever --- net/tls/tls_sw.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c index 5626fdd4ea0a..5fdd43a55f1e 100644 --- a/net/tls/tls_sw.c +++ b/net/tls/tls_sw.c @@ -2356,7 +2356,7 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc, goto read_sock_end; decrypted = 0; - do { + for (;;) { if (!skb_queue_empty(&ctx->rx_list)) { skb = __skb_dequeue(&ctx->rx_list); rxm = strp_msg(skb); @@ -2405,10 +2405,11 @@ int tls_sw_read_sock(struct sock *sk, read_descriptor_t *desc, goto read_sock_requeue; } else { consume_skb(skb); + skb = NULL; if (!desc->count) - skb = NULL; + break; } - } while (skb); + } read_sock_end: tls_rx_reader_release(sk, ctx); -- 2.53.0