From: Ido Schimmel <idosch@nvidia.com>
To: Daehyeon Ko <4ncienth@gmail.com>
Cc: David Ahern <dsahern@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@kernel.org>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
Simon Horman <horms@kernel.org>,
Vladimir Vdovin <deliran@verdict.gg>,
Donald Hunter <donald.hunter@gmail.com>,
Amit Cohen <amcohen@nvidia.com>, Roopa Prabhu <roopa@nvidia.com>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH net v2 2/3] ipv4: stop exception dump when nexthop group shrinks
Date: Sun, 4 Oct 2026 11:02:28 +0300 [thread overview]
Message-ID: <20261004080228.GA92032@shredder> (raw)
In-Reply-To: <5bb7bd97411eb9db454464bf449107395e760f26.1790915964.git.4ncienth@gmail.com>
On Fri, Oct 02, 2026 at 01:50:59PM +0900, Daehyeon Ko wrote:
> Commit 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU
> protection") allowed IPv4 FIB dumps to run concurrently with nexthop
> replacement.
>
> fib_dump_info_fnhe() uses fib_info_num_path() as the loop bound,
> then fib_info_nhc() independently reloads nh->nh_grp. If
> RTM_NEWNEXTHOP replaces a group with fewer paths between those loads,
> fib_info_nhc() returns NULL and the dump dereferences it through
> nhc_flags.
>
> Stop the walk when the indexed path is absent. Nexthop groups are
> dense, so the current snapshot has no later path.
>
> Fixes: 4ce5dc9316de ("inet: switch inet_dump_fib() to RCU protection")
> Reported-by: Ido Schimmel <idosch@nvidia.com>
> Link: https://lore.kernel.org/netdev/20261001170513.GA1657889@shredder/
> Cc: stable@vger.kernel.org
> Assisted-by: LLM
> Signed-off-by: Daehyeon Ko <4ncienth@gmail.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
next prev parent reply other threads:[~2026-10-04 8:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-02 4:50 [PATCH net v2 0/3] ipv4: handle nexthop group shrink races Daehyeon Ko
2026-10-02 4:50 ` [PATCH net v2 1/3] ipv4: stop PMTU walk when nexthop group shrinks Daehyeon Ko
2026-10-02 4:50 ` [PATCH net v2 2/3] ipv4: stop exception dump " Daehyeon Ko
2026-10-04 8:02 ` Ido Schimmel [this message]
2026-10-02 4:51 ` [PATCH net v2 3/3] ipv4: stop route notification sizing " Daehyeon Ko
2026-10-04 8:20 ` Ido Schimmel
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