From: Simon Horman <horms@kernel.org>
To: Long Li <longli@microsoft.com>
Cc: Konstantin Taranov <kotaranov@microsoft.com>,
Jakub Kicinski <kuba@kernel.org>,
"David S . Miller" <davem@davemloft.net>,
Paolo Abeni <pabeni@redhat.com>,
Eric Dumazet <edumazet@google.com>,
Andrew Lunn <andrew+netdev@lunn.ch>,
Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
Haiyang Zhang <haiyangz@microsoft.com>,
"K . Y . Srinivasan" <kys@microsoft.com>,
Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
shradhagupta@linux.microsoft.com, ernis@linux.microsoft.com,
stephen@networkplumber.org, shirazsaleem@microsoft.com,
netdev@vger.kernel.org, linux-rdma@vger.kernel.org,
linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, sdf@fomichev.me, daniel@iogearbox.net,
hawk@kernel.org, ast@kernel.org, john.fastabend@gmail.com
Subject: Re: [PATCH net] net: mana: restore the XDP program pointer when pre-allocation fails
Date: Tue, 8 Sep 2026 10:43:21 +0100 [thread overview]
Message-ID: <20260908094321.GR40544@horms.kernel.org> (raw)
In-Reply-To: <20260904202640.3900685-1-longli@microsoft.com>
On Fri, Sep 04, 2026 at 01:26:40PM -0700, Long Li wrote:
> mana_xdp_set() publishes the new program into apc->bpf_prog before it
> allocates anything, because mana_pre_alloc_rxbufs() sizes the buffers
> from it via mana_get_rxbuf_cfg(). When that allocation fails the
> function returns the error directly, skipping the err_dealloc_rxbuffs
> label which is the only place that restores the previous pointer.
>
> The attach is reported as failed, so the BPF core drops the reference it
> held for the caller and the program can be freed, while apc->bpf_prog
> still points at it. The next consumer of mana_xdp_get() - typically
> mana_chn_setxdp() from mana_alloc_queues() on the following ifup, or
> after a TX timeout reset - then calls bpf_prog_add() on freed memory.
>
> This is reachable from an ordinary "ip link set dev ethX xdp obj ..."
> whenever the per-queue RX buffer pre-allocation cannot be satisfied.
>
> Restore the previous program on that error path.
>
> Fixes: 730ff06d3f5c ("net: mana: Use page pool fragments for RX buffers instead of full pages to improve memory efficiency.")
> Signed-off-by: Long Li <longli@microsoft.com>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2026-09-08 9:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-04 20:26 Long Li
2026-09-08 9:43 ` Simon Horman [this message]
2026-09-10 15:20 ` patchwork-bot+netdevbpf
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