linux-kernel - [PATCH net v2] strparser: Fix signed/unsigned mismatch bug

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-ID: <20251106222835.1871628-1-nate.karstens@garmin.com>
Date: Thu, 6 Nov 2025 16:28:33 -0600
From: Nate Karstens <nate.karstens@...min.com>
To: <netdev@...r.kernel.org>
CC: Nate Karstens <nate.karstens@...min.com>,
        Nate Karstens
	<nate.karstens@...il.com>,
        Tom Herbert <tom@...ntonium.net>,
        Sabrina Dubroca
	<sd@...asysnail.net>,
        Jacob Keller <jacob.e.keller@...el.com>, <stable@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        "Eric
 Dumazet" <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>,
        Simon Horman <horms@...nel.org>,
        Martin KaFai Lau
	<martin.lau@...nel.org>,
        Jakub Sitnicki <jakub@...udflare.com>, Jiayuan Chen
	<mrpre@....com>,
        "Dr. David Alan Gilbert" <linux@...blig.org>,
        Tom Herbert
	<tom@...bertland.com>, <linux-kernel@...r.kernel.org>
Subject: [PATCH net v2] strparser: Fix signed/unsigned mismatch bug

The `len` member of the sk_buff is an unsigned int. This is cast to
`ssize_t` (a signed type) for the first sk_buff in the comparison,
but not the second sk_buff. On 32-bit systems, this can result in
an integer underflow for certain values because unsigned arithmetic
is being used.

This appears to be an oversight: if the intention was to use unsigned
arithmetic, then the first cast would have been omitted. The change
ensures both len values are cast to `ssize_t`.

The underflow causes an issue with ktls when multiple TLS PDUs are
included in a single TCP segment. The mainline kernel does not use
strparser for ktls anymore, but this is still useful for other
features that still use strparser, and for backporting.

Signed-off-by: Nate Karstens <nate.karstens@...min.com>
Cc: stable@...r.kernel.org
Fixes: 43a0c6751a32 ("strparser: Stream parser for messages")
---
 net/strparser/strparser.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/strparser/strparser.c b/net/strparser/strparser.c
index 43b1f558b33d..e659fea2da70 100644
--- a/net/strparser/strparser.c
+++ b/net/strparser/strparser.c
@@ -238,7 +238,7 @@ static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 				strp_parser_err(strp, -EMSGSIZE, desc);
 				break;
 			} else if (len <= (ssize_t)head->len -
-					  skb->len - stm->strp.offset) {
+					  (ssize_t)skb->len - stm->strp.offset) {
 				/* Length must be into new skb (and also
 				 * greater than zero)
 				 */
-- 
2.34.1