Re: [PATCH net v2] strparser: Fix signed/unsigned mismatch bug

[Sabrina Dubroca <sd@queasysnail.net>]

2025-11-06, 16:28:33 -0600, Nate Karstens wrote:
> 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")
> ---
>  net/strparser/strparser.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>

Thanks Nate.

-- 
Sabrina