From: David Laight <david.laight.linux@gmail.com>
To: bot+bpf-ci@kernel.org
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
dsahern@kernel.org, davem@davemloft.net, edumazet@google.com,
kuba@kernel.org, pabeni@redhat.com, ast@kernel.org,
andrii@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org,
eddyz87@gmail.com, yonghong.song@linux.dev, clm@meta.com,
ihor.solodrai@linux.dev
Subject: Re: [PATCH 09/44] ipv6: __ip6_append_data() don't abuse max_t() casts
Date: Thu, 20 Nov 2025 11:16:23 +0000 [thread overview]
Message-ID: <20251120111623.44ebfae7@pumpkin> (raw)
In-Reply-To: <ddcd920ff99e0f97ed2c92cf650872d76a4b7404ea87a104e6ab061ee3005cf9@mail.kernel.org>
On Thu, 20 Nov 2025 00:32:34 +0000 (UTC)
bot+bpf-ci@kernel.org wrote:
> > diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> > index f904739e9..6fecf2f2c 100644
> > --- a/net/ipv6/ip6_output.c
> > +++ b/net/ipv6/ip6_output.c
> > @@ -1440,7 +1440,7 @@ static int __ip6_append_data(struct sock *sk,
> > struct sk_buff *skb, *skb_prev = NULL;
> > struct inet_cork *cork = &cork_full->base;
> > struct flowi6 *fl6 = &cork_full->fl.u.ip6;
> > - unsigned int maxfraglen, fragheaderlen, mtu, orig_mtu, pmtu;
> > + unsigned int maxfraglen, fragheaderlen, mtu, orig_mtu;
>
> [ ... ]
>
> > @@ -1504,9 +1504,10 @@ static int __ip6_append_data(struct sock *sk,
> > maxnonfragsize = mtu;
> >
> > if (cork->length + length > maxnonfragsize - headersize) {
> > + int pmtu;
> > emsgsize:
> > - pmtu = max_t(int, mtu - headersize + sizeof(struct ipv6hdr), 0);
> > - ipv6_local_error(sk, EMSGSIZE, fl6, pmtu);
> > + pmtu = mtu - headersize + (int)sizeof(struct ipv6hdr);
> > + ipv6_local_error(sk, EMSGSIZE, fl6, max(pmtu, 0));
> > return -EMSGSIZE;
> > }
>
> Can the variable pmtu be used uninitialized here?
If your AI bot doesn't understand code don't run it.
David
>
> When reaching the emsgsize label via goto statements from earlier in
> __ip6_append_data() (the checks at lines around mtu <= fragheaderlen,
> headersize + transhdrlen > mtu, and the dontfrag check), the int pmtu
> declaration is skipped. This leaves pmtu uninitialized when it's used
> in the calculation that's passed to ipv6_local_error().
>
>
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
>
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/19519124312
next prev parent reply other threads:[~2025-11-20 11:16 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-19 22:40 [PATCH 00/44] Change a lot of min_t() that might mask high bits david.laight.linux
2025-11-19 22:41 ` [PATCH 07/44] net/core/flow_dissector: Fix cap of __skb_flow_dissect() return value david.laight.linux
2025-11-19 22:41 ` [PATCH 08/44] net: ethtool: Use min3() instead of nested min_t(u16,...) david.laight.linux
2025-11-19 22:41 ` [PATCH 09/44] ipv6: __ip6_append_data() don't abuse max_t() casts david.laight.linux
2025-11-20 0:32 ` bot+bpf-ci
2025-11-20 11:16 ` David Laight [this message]
2025-11-20 13:50 ` Chris Mason
2025-11-19 22:41 ` [PATCH 21/44] drivers/net/ethernet/realtek: use min() instead of min_t() david.laight.linux
2025-11-19 22:41 ` [PATCH 40/44] net: Don't pass bitfields to max_t() david.laight.linux
2025-11-19 22:41 ` [PATCH 41/44] net/core: Change loop conditions so min() can be used david.laight.linux
2025-11-19 22:41 ` [PATCH 42/44] net: use min() instead of min_t() david.laight.linux
2025-11-19 22:41 ` [PATCH 43/44] net/netlink: Use umin() to avoid min_t(int, ...) discarding high bits david.laight.linux
2025-11-19 22:41 ` [PATCH 44/44] net/mptcp: Change some dubious min_t(int, ...) to min() david.laight.linux
2025-12-18 17:33 ` Matthieu Baerts
2025-12-18 20:15 ` David Laight
2025-12-19 10:48 ` Matthieu Baerts
2025-11-20 1:47 ` [PATCH 00/44] Change a lot of min_t() that might mask high bits Jakub Kicinski
2025-11-20 9:38 ` Lorenzo Stoakes
2025-11-20 14:52 ` (subset) " Jens Axboe
2025-11-24 9:49 ` Herbert Xu
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