netdev - [PATCH net] tls: always refresh the queue when reading sock

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Message-ID: <20250716143850.1520292-1-kuba@kernel.org>
Date: Wed, 16 Jul 2025 07:38:50 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: davem@...emloft.net
Cc: netdev@...r.kernel.org,
	edumazet@...gle.com,
	pabeni@...hat.com,
	andrew+netdev@...n.ch,
	horms@...nel.org,
	Jakub Kicinski <kuba@...nel.org>,
	borisp@...dia.com,
	john.fastabend@...il.com
Subject: [PATCH net] tls: always refresh the queue when reading sock

After recent changes in net-next TCP compacts skbs much more
aggressively. This unearthed a bug in TLS where we may try
to operate on an old skb when checking if all skbs in the
queue have matching decrypt state and geometry.

    BUG: KASAN: slab-use-after-free in tls_strp_check_rcv+0x898/0x9a0 [tls]
    (net/tls/tls_strp.c:436 net/tls/tls_strp.c:530 net/tls/tls_strp.c:544)
    Read of size 4 at addr ffff888013085750 by task tls/13529

    CPU: 2 UID: 0 PID: 13529 Comm: tls Not tainted 6.16.0-rc5-virtme
    Call Trace:
     kasan_report+0xca/0x100
     tls_strp_check_rcv+0x898/0x9a0 [tls]
     tls_rx_rec_wait+0x2c9/0x8d0 [tls]
     tls_sw_recvmsg+0x40f/0x1aa0 [tls]
     inet_recvmsg+0x1c3/0x1f0

Always reload the queue, fast path is to have the record in the queue
when we wake, anyway (IOW the path going down "if !strp->stm.full_len").

Fixes: 0d87bbd39d7f ("tls: strp: make sure the TCP skbs do not have overlapping data")
Signed-off-by: Jakub Kicinski <kuba@...nel.org>
---
CC: borisp@...dia.com
CC: john.fastabend@...il.com
---
 net/tls/tls_strp.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/net/tls/tls_strp.c b/net/tls/tls_strp.c
index 65b0da6fdf6a..095cf31bae0b 100644
--- a/net/tls/tls_strp.c
+++ b/net/tls/tls_strp.c
@@ -512,9 +512,8 @@ static int tls_strp_read_sock(struct tls_strparser *strp)
 	if (inq < strp->stm.full_len)
 		return tls_strp_read_copy(strp, true);
 
+	tls_strp_load_anchor_with_queue(strp, inq);
 	if (!strp->stm.full_len) {
-		tls_strp_load_anchor_with_queue(strp, inq);
-
 		sz = tls_rx_msg_size(strp, strp->anchor);
 		if (sz < 0) {
 			tls_strp_abort_strp(strp, sz);
-- 
2.50.1