From: Maciej Fijalkowski maciej.fijalkowski@intel.com
[ Upstream commit 1596dae2f17ec5c6e8c8f0e3fec78c5ae55c1e0b ]
Xsk Tx can be triggered via either sendmsg() or poll() syscalls. These two paths share a call to common function xsk_xmit() which has two sanity checks within. A pseudo code example to show the two paths:
__xsk_sendmsg() : xsk_poll(): if (unlikely(!xsk_is_bound(xs))) if (unlikely(!xsk_is_bound(xs))) return -ENXIO; return mask; if (unlikely(need_wait)) (...) return -EOPNOTSUPP; xsk_xmit() mark napi id (...) xsk_xmit()
xsk_xmit(): if (unlikely(!(xs->dev->flags & IFF_UP))) return -ENETDOWN; if (unlikely(!xs->tx)) return -ENOBUFS;
As it can be observed above, in sendmsg() napi id can be marked on interface that was not brought up and this causes a NULL ptr dereference:
[31757.505631] BUG: kernel NULL pointer dereference, address: 0000000000000018 [31757.512710] #PF: supervisor read access in kernel mode [31757.517936] #PF: error_code(0x0000) - not-present page [31757.523149] PGD 0 P4D 0 [31757.525726] Oops: 0000 [#1] PREEMPT SMP NOPTI [31757.530154] CPU: 26 PID: 95641 Comm: xdpsock Not tainted 6.2.0-rc5+ #40 [31757.536871] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019 [31757.547457] RIP: 0010:xsk_sendmsg+0xde/0x180 [31757.551799] Code: 00 75 a2 48 8b 00 a8 04 75 9b 84 d2 74 69 8b 85 14 01 00 00 85 c0 75 1b 48 8b 85 28 03 00 00 48 8b 80 98 00 00 00 48 8b 40 20 <8b> 40 18 89 85 14 01 00 00 8b bd 14 01 00 00 81 ff 00 01 00 00 0f [31757.570840] RSP: 0018:ffffc90034f27dc0 EFLAGS: 00010246 [31757.576143] RAX: 0000000000000000 RBX: ffffc90034f27e18 RCX: 0000000000000000 [31757.583389] RDX: 0000000000000001 RSI: ffffc90034f27e18 RDI: ffff88984cf3c100 [31757.590631] RBP: ffff88984714a800 R08: ffff88984714a800 R09: 0000000000000000 [31757.597877] R10: 0000000000000001 R11: 0000000000000000 R12: 00000000fffffffa [31757.605123] R13: 0000000000000000 R14: 0000000000000003 R15: 0000000000000000 [31757.612364] FS: 00007fb4c5931180(0000) GS:ffff88afdfa00000(0000) knlGS:0000000000000000 [31757.620571] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [31757.626406] CR2: 0000000000000018 CR3: 000000184b41c003 CR4: 00000000007706e0 [31757.633648] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [31757.640894] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [31757.648139] PKRU: 55555554 [31757.650894] Call Trace: [31757.653385] <TASK> [31757.655524] sock_sendmsg+0x8f/0xa0 [31757.659077] ? sockfd_lookup_light+0x12/0x70 [31757.663416] __sys_sendto+0xfc/0x170 [31757.667051] ? do_sched_setscheduler+0xdb/0x1b0 [31757.671658] __x64_sys_sendto+0x20/0x30 [31757.675557] do_syscall_64+0x38/0x90 [31757.679197] entry_SYSCALL_64_after_hwframe+0x72/0xdc [31757.687969] Code: 8e f6 ff 44 8b 4c 24 2c 4c 8b 44 24 20 41 89 c4 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 3a 44 89 e7 48 89 44 24 08 e8 b5 8e f6 ff 48 [31757.707007] RSP: 002b:00007ffd49c73c70 EFLAGS: 00000293 ORIG_RAX: 000000000000002c [31757.714694] RAX: ffffffffffffffda RBX: 000055a996565380 RCX: 00007fb4c5727c16 [31757.721939] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 [31757.729184] RBP: 0000000000000040 R08: 0000000000000000 R09: 0000000000000000 [31757.736429] R10: 0000000000000040 R11: 0000000000000293 R12: 0000000000000000 [31757.743673] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [31757.754940] </TASK>
To fix this, let's make xsk_xmit a function that will be responsible for generic Tx, where RCU is handled accordingly and pull out sanity checks and xs->zc handling. Populate sanity checks to __xsk_sendmsg() and xsk_poll().
Fixes: ca2e1a627035 ("xsk: Mark napi_id on sendmsg()") Fixes: 18b1ab7aa76b ("xsk: Fix race at socket teardown") Signed-off-by: Maciej Fijalkowski maciej.fijalkowski@intel.com Reviewed-by: Alexander Lobakin aleksander.lobakin@intel.com Link: https://lore.kernel.org/r/20230215143309.13145-1-maciej.fijalkowski@intel.co... Signed-off-by: Martin KaFai Lau martin.lau@kernel.org Signed-off-by: Daniel Borkmann daniel@iogearbox.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/xdp/xsk.c | 59 ++++++++++++++++++++++++++++----------------------- 1 file changed, 33 insertions(+), 26 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c index 9f0561b67c12e..13f62d2402e71 100644 --- a/net/xdp/xsk.c +++ b/net/xdp/xsk.c @@ -511,7 +511,7 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs, return skb; }
-static int xsk_generic_xmit(struct sock *sk) +static int __xsk_generic_xmit(struct sock *sk) { struct xdp_sock *xs = xdp_sk(sk); u32 max_batch = TX_BATCH_SIZE; @@ -594,22 +594,13 @@ static int xsk_generic_xmit(struct sock *sk) return err; }
-static int xsk_xmit(struct sock *sk) +static int xsk_generic_xmit(struct sock *sk) { - struct xdp_sock *xs = xdp_sk(sk); int ret;
- if (unlikely(!(xs->dev->flags & IFF_UP))) - return -ENETDOWN; - if (unlikely(!xs->tx)) - return -ENOBUFS; - - if (xs->zc) - return xsk_wakeup(xs, XDP_WAKEUP_TX); - /* Drop the RCU lock since the SKB path might sleep. */ rcu_read_unlock(); - ret = xsk_generic_xmit(sk); + ret = __xsk_generic_xmit(sk); /* Reaquire RCU lock before going into common code. */ rcu_read_lock();
@@ -627,17 +618,31 @@ static bool xsk_no_wakeup(struct sock *sk) #endif }
+static int xsk_check_common(struct xdp_sock *xs) +{ + if (unlikely(!xsk_is_bound(xs))) + return -ENXIO; + if (unlikely(!(xs->dev->flags & IFF_UP))) + return -ENETDOWN; + + return 0; +} + static int __xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len) { bool need_wait = !(m->msg_flags & MSG_DONTWAIT); struct sock *sk = sock->sk; struct xdp_sock *xs = xdp_sk(sk); struct xsk_buff_pool *pool; + int err;
- if (unlikely(!xsk_is_bound(xs))) - return -ENXIO; + err = xsk_check_common(xs); + if (err) + return err; if (unlikely(need_wait)) return -EOPNOTSUPP; + if (unlikely(!xs->tx)) + return -ENOBUFS;
if (sk_can_busy_loop(sk)) { if (xs->zc) @@ -649,8 +654,11 @@ static int __xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len return 0;
pool = xs->pool; - if (pool->cached_need_wakeup & XDP_WAKEUP_TX) - return xsk_xmit(sk); + if (pool->cached_need_wakeup & XDP_WAKEUP_TX) { + if (xs->zc) + return xsk_wakeup(xs, XDP_WAKEUP_TX); + return xsk_generic_xmit(sk); + } return 0; }
@@ -670,11 +678,11 @@ static int __xsk_recvmsg(struct socket *sock, struct msghdr *m, size_t len, int bool need_wait = !(flags & MSG_DONTWAIT); struct sock *sk = sock->sk; struct xdp_sock *xs = xdp_sk(sk); + int err;
- if (unlikely(!xsk_is_bound(xs))) - return -ENXIO; - if (unlikely(!(xs->dev->flags & IFF_UP))) - return -ENETDOWN; + err = xsk_check_common(xs); + if (err) + return err; if (unlikely(!xs->rx)) return -ENOBUFS; if (unlikely(need_wait)) @@ -713,21 +721,20 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock, sock_poll_wait(file, sock, wait);
rcu_read_lock(); - if (unlikely(!xsk_is_bound(xs))) { - rcu_read_unlock(); - return mask; - } + if (xsk_check_common(xs)) + goto skip_tx;
pool = xs->pool;
if (pool->cached_need_wakeup) { if (xs->zc) xsk_wakeup(xs, pool->cached_need_wakeup); - else + else if (xs->tx) /* Poll needs to drive Tx also in copy mode */ - xsk_xmit(sk); + xsk_generic_xmit(sk); }
+skip_tx: if (xs->rx && !xskq_prod_is_empty(xs->rx)) mask |= EPOLLIN | EPOLLRDNORM; if (xs->tx && xsk_tx_writeable(xs))