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strparser: Fix signed/unsigned mismatch bug

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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@garmin.com>
Cc: stable@vger.kernel.org
Fixes: 43a0c6751a32 ("strparser: Stream parser for messages")
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/20251106222835.1871628-1-nate.karstens@garmin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Nate Karstens 2025-11-06 16:28:33 -06:00 committed by Jakub Kicinski
parent 74d4432421
commit 4da4e4bde1
1 changed files with 1 additions and 1 deletions
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2
net/strparser/strparser.c
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@ -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)
*/