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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , stable@vger.kernel.org, Jan Beulich Subject: [PATCH v2] xen/netback: avoid entering xenvif_rx_next_skb() with an empty rx queue Date: Wed, 13 Jul 2022 15:53:22 +0200 Message-Id: <20220713135322.19616-1-jgross@suse.com> X-Mailer: git-send-email 2.35.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMail-DKIM: pass (identity @suse.com) X-ZM-MESSAGEID: 1657720427841100001 Content-Type: text/plain; charset="utf-8" xenvif_rx_next_skb() is expecting the rx queue not being empty, but in case the loop in xenvif_rx_action() is doing multiple iterations, the availability of another skb in the rx queue is not being checked. This can lead to crashes: [40072.537261] BUG: unable to handle kernel NULL pointer dereference at 000= 0000000000080 [40072.537407] IP: xenvif_rx_skb+0x23/0x590 [xen_netback] [40072.537534] PGD 0 P4D 0 [40072.537644] Oops: 0000 [#1] SMP NOPTI [40072.537749] CPU: 0 PID: 12505 Comm: v1-c40247-q2-gu Not tainted 4.12.14-= 122.121-default #1 SLE12-SP5 [40072.537867] Hardware name: HP ProLiant DL580 Gen9/ProLiant DL580 Gen9, B= IOS U17 11/23/2021 [40072.537999] task: ffff880433b38100 task.stack: ffffc90043d40000 [40072.538112] RIP: e030:xenvif_rx_skb+0x23/0x590 [xen_netback] [40072.538217] RSP: e02b:ffffc90043d43de0 EFLAGS: 00010246 [40072.538319] RAX: 0000000000000000 RBX: ffffc90043cd7cd0 RCX: 00000000000= 000f7 [40072.538430] RDX: 0000000000000000 RSI: 0000000000000006 RDI: ffffc90043d= 43df8 [40072.538531] RBP: 000000000000003f R08: 000077ff80000000 R09: 00000000000= 00008 [40072.538644] R10: 0000000000007ff0 R11: 00000000000008f6 R12: ffffc90043c= e2708 [40072.538745] R13: 0000000000000000 R14: ffffc90043d43ed0 R15: ffff88043ea= 748c0 [40072.538861] FS: 0000000000000000(0000) GS:ffff880484600000(0000) knlGS:0= 000000000000000 [40072.538988] CS: e033 DS: 0000 ES: 0000 CR0: 0000000080050033 [40072.539088] CR2: 0000000000000080 CR3: 0000000407ac8000 CR4: 00000000000= 40660 [40072.539211] Call Trace: [40072.539319] xenvif_rx_action+0x71/0x90 [xen_netback] [40072.539429] xenvif_kthread_guest_rx+0x14a/0x29c [xen_netback] Fix that by stopping the loop in case the rx queue becomes empty. Cc: stable@vger.kernel.org Fixes: 98f6d57ced73 ("xen-netback: process guest rx packets in batches") Signed-off-by: Juergen Gross Reviewed-by: Jan Beulich Reviewed-by: Paul Durrant --- V2: - modified patch title (Jan Beulich) - added Fixes: (Jan Beulich) --- drivers/net/xen-netback/rx.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/xen-netback/rx.c b/drivers/net/xen-netback/rx.c index dbac4c03d21a..a0335407be42 100644 --- a/drivers/net/xen-netback/rx.c +++ b/drivers/net/xen-netback/rx.c @@ -495,6 +495,7 @@ void xenvif_rx_action(struct xenvif_queue *queue) queue->rx_copy.completed =3D &completed_skbs; =20 while (xenvif_rx_ring_slots_available(queue) && + !skb_queue_empty(&queue->rx_queue) && work_done < RX_BATCH_SIZE) { xenvif_rx_skb(queue); work_done++; --=20 2.35.3