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Date: Tue, 26 Apr 2022 11:01:26 +0200
From: Magnus Karlsson <magnus.karlsson@...il.com>
To: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc: bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, andriin@...nel.org,
Network Development <netdev@...r.kernel.org>,
"Karlsson, Magnus" <magnus.karlsson@...el.com>
Subject: Re: [PATCH bpf] xsk: fix possible crash when multiple sockets are created
On Tue, Apr 26, 2022 at 12:28 AM Maciej Fijalkowski
<maciej.fijalkowski@...el.com> wrote:
>
> Fix a crash that happens if an Rx only socket is created first, then a
> second socket is created that is Tx only and bound to the same umem as
> the first socket and also the same netdev and queue_id together with the
> XDP_SHARED_UMEM flag. In this specific case, the tx_descs array page
> pool was not created by the first socket as it was an Rx only socket.
> When the second socket is bound it needs this tx_descs array of this
> shared page pool as it has a Tx component, but unfortunately it was
> never allocated, leading to a crash. Note that this array is only used
> for zero-copy drivers using the batched Tx APIs, currently only ice and
> i40e.
>
> [ 5511.150360] BUG: kernel NULL pointer dereference, address: 0000000000000008
> [ 5511.158419] #PF: supervisor write access in kernel mode
> [ 5511.164472] #PF: error_code(0x0002) - not-present page
> [ 5511.170416] PGD 0 P4D 0
> [ 5511.173347] Oops: 0002 [#1] PREEMPT SMP PTI
> [ 5511.178186] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G E 5.18.0-rc1+ #97
> [ 5511.187245] Hardware name: Intel Corp. GRANTLEY/GRANTLEY, BIOS GRRFCRB1.86B.0276.D07.1605190235 05/19/2016
> [ 5511.198418] RIP: 0010:xsk_tx_peek_release_desc_batch+0x198/0x310
> [ 5511.205375] Code: c0 83 c6 01 84 c2 74 6d 8d 46 ff 23 07 44 89 e1 48 83 c0 14 48 c1 e1 04 48 c1 e0 04 48 03 47 10 4c 01 c1 48 8b 50 08 48 8b 00 <48> 89 51 08 48 89 01 41 80 bd d7 00 00 00 00 75 82 48 8b 19 49 8b
> [ 5511.227091] RSP: 0018:ffffc90000003dd0 EFLAGS: 00010246
> [ 5511.233135] RAX: 0000000000000000 RBX: ffff88810c8da600 RCX: 0000000000000000
> [ 5511.241384] RDX: 000000000000003c RSI: 0000000000000001 RDI: ffff888115f555c0
> [ 5511.249634] RBP: ffffc90000003e08 R08: 0000000000000000 R09: ffff889092296b48
> [ 5511.257886] R10: 0000ffffffffffff R11: ffff889092296800 R12: 0000000000000000
> [ 5511.266138] R13: ffff88810c8db500 R14: 0000000000000040 R15: 0000000000000100
> [ 5511.274387] FS: 0000000000000000(0000) GS:ffff88903f800000(0000) knlGS:0000000000000000
> [ 5511.283746] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 5511.290389] CR2: 0000000000000008 CR3: 00000001046e2001 CR4: 00000000003706f0
> [ 5511.298640] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> [ 5511.306892] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> [ 5511.315142] Call Trace:
> [ 5511.317972] <IRQ>
> [ 5511.320301] ice_xmit_zc+0x68/0x2f0 [ice]
> [ 5511.324977] ? ktime_get+0x38/0xa0
> [ 5511.328913] ice_napi_poll+0x7a/0x6a0 [ice]
> [ 5511.333784] __napi_poll+0x2c/0x160
> [ 5511.337821] net_rx_action+0xdd/0x200
> [ 5511.342058] __do_softirq+0xe6/0x2dd
> [ 5511.346198] irq_exit_rcu+0xb5/0x100
> [ 5511.350339] common_interrupt+0xa4/0xc0
> [ 5511.354777] </IRQ>
> [ 5511.357201] <TASK>
> [ 5511.359625] asm_common_interrupt+0x1e/0x40
> [ 5511.364466] RIP: 0010:cpuidle_enter_state+0xd2/0x360
> [ 5511.370211] Code: 49 89 c5 0f 1f 44 00 00 31 ff e8 e9 00 7b ff 45 84 ff 74 12 9c 58 f6 c4 02 0f 85 72 02 00 00 31 ff e8 02 0c 80 ff fb 45 85 f6 <0f> 88 11 01 00 00 49 63 c6 4c 2b 2c 24 48 8d 14 40 48 8d 14 90 49
> [ 5511.391921] RSP: 0018:ffffffff82a03e60 EFLAGS: 00000202
> [ 5511.397962] RAX: ffff88903f800000 RBX: 0000000000000001 RCX: 000000000000001f
> [ 5511.406214] RDX: 0000000000000000 RSI: ffffffff823400b9 RDI: ffffffff8234c046
> [ 5511.424646] RBP: ffff88810a384800 R08: 000005032a28c046 R09: 0000000000000008
> [ 5511.443233] R10: 000000000000000b R11: 0000000000000006 R12: ffffffff82bcf700
> [ 5511.461922] R13: 000005032a28c046 R14: 0000000000000001 R15: 0000000000000000
> [ 5511.480300] cpuidle_enter+0x29/0x40
> [ 5511.494329] do_idle+0x1c7/0x250
> [ 5511.507610] cpu_startup_entry+0x19/0x20
> [ 5511.521394] start_kernel+0x649/0x66e
> [ 5511.534626] secondary_startup_64_no_verify+0xc3/0xcb
> [ 5511.549230] </TASK>
>
> Detect such case during bind() and allocate this memory region via newly
> introduced xp_alloc_tx_descs(). Also, use kvcalloc instead of kcalloc as
> for other buffer pool allocations, so that it matches the kvfree() from
> xp_destroy().
Thank you for this fix Maciej.
Acked-by: Magnus Karlsson <magnus.karlsson@...el.com>
> Fixes: d1bc532e99be ("i40e: xsk: Move tmp desc array from driver to pool")
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> ---
> include/net/xsk_buff_pool.h | 1 +
> net/xdp/xsk.c | 13 +++++++++++++
> net/xdp/xsk_buff_pool.c | 16 ++++++++++++----
> 3 files changed, 26 insertions(+), 4 deletions(-)
>
> diff --git a/include/net/xsk_buff_pool.h b/include/net/xsk_buff_pool.h
> index 5554ee75e7da..647722e847b4 100644
> --- a/include/net/xsk_buff_pool.h
> +++ b/include/net/xsk_buff_pool.h
> @@ -97,6 +97,7 @@ int xp_assign_dev(struct xsk_buff_pool *pool, struct net_device *dev,
> u16 queue_id, u16 flags);
> int xp_assign_dev_shared(struct xsk_buff_pool *pool, struct xdp_umem *umem,
> struct net_device *dev, u16 queue_id);
> +int xp_alloc_tx_descs(struct xsk_buff_pool *pool, struct xdp_sock *xs);
> void xp_destroy(struct xsk_buff_pool *pool);
> void xp_get_pool(struct xsk_buff_pool *pool);
> bool xp_put_pool(struct xsk_buff_pool *pool);
> diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
> index 040c73345b7c..57afb96c41e8 100644
> --- a/net/xdp/xsk.c
> +++ b/net/xdp/xsk.c
> @@ -967,6 +967,19 @@ static int xsk_bind(struct socket *sock, struct sockaddr *addr, int addr_len)
>
> xp_get_pool(umem_xs->pool);
> xs->pool = umem_xs->pool;
> +
> + /* If underlying shared umem was created without Tx
> + * ring, allocate Tx descs array that Tx batching API
> + * utilizes
> + */
> + if (xs->tx && !xs->pool->tx_descs) {
> + err = xp_alloc_tx_descs(xs->pool, xs);
> + if (err) {
> + xp_put_pool(xs->pool);
> + sockfd_put(sock);
> + goto out_unlock;
> + }
> + }
> }
>
> xdp_get_umem(umem_xs->umem);
> diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
> index af040ffa14ff..87bdd71c7bb6 100644
> --- a/net/xdp/xsk_buff_pool.c
> +++ b/net/xdp/xsk_buff_pool.c
> @@ -42,6 +42,16 @@ void xp_destroy(struct xsk_buff_pool *pool)
> kvfree(pool);
> }
>
> +int xp_alloc_tx_descs(struct xsk_buff_pool *pool, struct xdp_sock *xs)
> +{
> + pool->tx_descs = kvcalloc(xs->tx->nentries, sizeof(*pool->tx_descs),
> + GFP_KERNEL);
> + if (!pool->tx_descs)
> + return -ENOMEM;
> +
> + return 0;
> +}
> +
> struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
> struct xdp_umem *umem)
> {
> @@ -59,11 +69,9 @@ struct xsk_buff_pool *xp_create_and_assign_umem(struct xdp_sock *xs,
> if (!pool->heads)
> goto out;
>
> - if (xs->tx) {
> - pool->tx_descs = kcalloc(xs->tx->nentries, sizeof(*pool->tx_descs), GFP_KERNEL);
> - if (!pool->tx_descs)
> + if (xs->tx)
> + if (xp_alloc_tx_descs(pool, xs))
> goto out;
> - }
>
> pool->chunk_mask = ~((u64)umem->chunk_size - 1);
> pool->addrs_cnt = umem->size;
> --
> 2.27.0
>
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