From: David Ahern <dsahern@kernel.org>
To: Eric Dumazet <edumazet@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>
Cc: Simon Horman <horms@kernel.org>,
Willem de Bruijn <willemb@google.com>,
Ido Schimmel <idosch@nvidia.com>,
netdev@vger.kernel.org, edumazet@google.com
Subject: Re: [PATCH net 1/2] ipv4: fix IP ID reuse in ip_select_ident_segs()
Date: Wed, 30 Sep 2026 06:30:10 -0600 [thread overview]
Message-ID: <855537d4-5c35-4bcb-aa58-82aa981e46fc@kernel.org> (raw)
In-Reply-To: <20260929131247.401104-2-edumazet@kernel.org>
On 9/29/26 8:12 AM, Eric Dumazet wrote:
> ip_select_ident_segs() must put the first of the @segs reserved IP IDs
> in iph->id, as GSO assigns id, id + 1, ..., id + segs - 1 to segments.
>
> Commit f866fbc842de ("ipv4: fix data-races around inet->inet_id")
> used atomic_add_return() for non-TCP sockets, which returns the first
> ID of the next packet instead. Consecutive GSO packets can then reuse
> IP IDs.
>
> SCTP GSO is affected. Other callers use segs == 1, and only see
> a harmless off-by-one (UDP GSO has a separate, older issue, see
> following patch in this series).
>
> Use atomic_fetch_add() instead, like the TCP path.
>
> Fixes: f866fbc842de ("ipv4: fix data-races around inet->inet_id")
> Signed-off-by: Eric Dumazet <edumazet@kernel.org>
> ---
> include/net/ip.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
Reviewed-by: David Ahern <dsahern@kernel.org>
next prev parent reply other threads:[~2026-09-30 12:30 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-29 13:12 [PATCH net 0/2] ipv4: fix IP ID reuse for GSO packets Eric Dumazet
2026-09-29 13:12 ` [PATCH net 1/2] ipv4: fix IP ID reuse in ip_select_ident_segs() Eric Dumazet
2026-09-30 6:20 ` Jiayuan Chen
2026-09-30 12:30 ` David Ahern [this message]
2026-09-29 13:12 ` [PATCH net 2/2] ipv4: reserve one IP ID per segment for UDP GSO packets Eric Dumazet
2026-09-30 6:18 ` Jiayuan Chen
2026-09-30 12:28 ` David Ahern
2026-09-30 12:58 ` Eric Dumazet
2026-09-30 13:50 ` David Ahern
2026-09-30 14:24 ` Eric Dumazet
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