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Message-ID: <20250731184829.1433735-1-kuniyu@google.com>
Date: Thu, 31 Jul 2025 18:48:13 +0000
From: Kuniyuki Iwashima <kuniyu@...gle.com>
To: Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>
Cc: Breno Leitao <leitao@...ian.org>, Kuniyuki Iwashima <kuniyu@...gle.com>,
Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org,
syzbot+8aa80c6232008f7b957d@...kaller.appspotmail.com
Subject: [PATCH v1 net] netdevsim: Fix wild pointer access in nsim_queue_free().
syzbot reported the splat below. [0]
When nsim_queue_uninit() is called from nsim_init_netdevsim(),
register_netdevice() has not been called, thus dev->dstats has
not been allocated.
Let's not call dev_dstats_rx_dropped_add() in such a case.
[0]
BUG: unable to handle page fault for address: ffff88809782c020
PF: supervisor write access in kernel mode
PF: error_code(0x0002) - not-present page
PGD 1b401067 P4D 1b401067 PUD 0
Oops: Oops: 0002 [#1] SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 8476 Comm: syz.1.251 Not tainted 6.16.0-syzkaller-06699-ge8d780dcd957 #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:local_add arch/x86/include/asm/local.h:33 [inline]
RIP: 0010:u64_stats_add include/linux/u64_stats_sync.h:89 [inline]
RIP: 0010:dev_dstats_rx_dropped_add include/linux/netdevice.h:3027 [inline]
RIP: 0010:nsim_queue_free+0xba/0x120 drivers/net/netdevsim/netdev.c:714
Code: 07 77 6c 4a 8d 3c ed 20 7e f1 8d 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 75 46 4a 03 1c ed 20 7e f1 8d <4c> 01 63 20 be 00 02 00 00 48 8d 3d 00 00 00 00 e8 61 2f 58 fa 48
RSP: 0018:ffffc900044af150 EFLAGS: 00010286
RAX: dffffc0000000000 RBX: ffff88809782c000 RCX: 00000000000079c3
RDX: 1ffffffff1be2fc7 RSI: ffffffff8c15f380 RDI: ffffffff8df17e38
RBP: ffff88805f59d000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000
R13: 0000000000000003 R14: ffff88806ceb3d00 R15: ffffed100dfd308e
FS: 0000000000000000(0000) GS:ffff88809782c000(0063) knlGS:00000000f505db40
CS: 0010 DS: 002b ES: 002b CR0: 0000000080050033
CR2: ffff88809782c020 CR3: 000000006fc6a000 CR4: 0000000000352ef0
Call Trace:
<TASK>
nsim_queue_uninit drivers/net/netdevsim/netdev.c:993 [inline]
nsim_init_netdevsim drivers/net/netdevsim/netdev.c:1049 [inline]
nsim_create+0xd0a/0x1260 drivers/net/netdevsim/netdev.c:1101
__nsim_dev_port_add+0x435/0x7d0 drivers/net/netdevsim/dev.c:1438
nsim_dev_port_add_all drivers/net/netdevsim/dev.c:1494 [inline]
nsim_dev_reload_create drivers/net/netdevsim/dev.c:1546 [inline]
nsim_dev_reload_up+0x5b8/0x860 drivers/net/netdevsim/dev.c:1003
devlink_reload+0x322/0x7c0 net/devlink/dev.c:474
devlink_nl_reload_doit+0xe31/0x1410 net/devlink/dev.c:584
genl_family_rcv_msg_doit+0x206/0x2f0 net/netlink/genetlink.c:1115
genl_family_rcv_msg net/netlink/genetlink.c:1195 [inline]
genl_rcv_msg+0x55c/0x800 net/netlink/genetlink.c:1210
netlink_rcv_skb+0x155/0x420 net/netlink/af_netlink.c:2552
genl_rcv+0x28/0x40 net/netlink/genetlink.c:1219
netlink_unicast_kernel net/netlink/af_netlink.c:1320 [inline]
netlink_unicast+0x5aa/0x870 net/netlink/af_netlink.c:1346
netlink_sendmsg+0x8d1/0xdd0 net/netlink/af_netlink.c:1896
sock_sendmsg_nosec net/socket.c:714 [inline]
__sock_sendmsg net/socket.c:729 [inline]
____sys_sendmsg+0xa95/0xc70 net/socket.c:2614
___sys_sendmsg+0x134/0x1d0 net/socket.c:2668
__sys_sendmsg+0x16d/0x220 net/socket.c:2700
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0x7c/0x3a0 arch/x86/entry/syscall_32.c:306
do_fast_syscall_32+0x32/0x80 arch/x86/entry/syscall_32.c:331
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf708e579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f505d55c EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000007 RCX: 0000000080000080
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>
Modules linked in:
CR2: ffff88809782c020
Fixes: 2a68a22304f9 ("netdevsim: account dropped packet length in stats on queue free")
Reported-by: syzbot+8aa80c6232008f7b957d@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/688bb9ca.a00a0220.26d0e1.0050.GAE@google.com/
Signed-off-by: Kuniyuki Iwashima <kuniyu@...gle.com>
---
drivers/net/netdevsim/netdev.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/drivers/net/netdevsim/netdev.c b/drivers/net/netdevsim/netdev.c
index 39fe28af48b9..5cbc005136d8 100644
--- a/drivers/net/netdevsim/netdev.c
+++ b/drivers/net/netdevsim/netdev.c
@@ -710,9 +710,13 @@ static struct nsim_rq *nsim_queue_alloc(void)
static void nsim_queue_free(struct net_device *dev, struct nsim_rq *rq)
{
hrtimer_cancel(&rq->napi_timer);
- local_bh_disable();
- dev_dstats_rx_dropped_add(dev, rq->skb_queue.qlen);
- local_bh_enable();
+
+ if (likely(dev->reg_state != NETREG_UNINITIALIZED)) {
+ local_bh_disable();
+ dev_dstats_rx_dropped_add(dev, rq->skb_queue.qlen);
+ local_bh_enable();
+ }
+
skb_queue_purge_reason(&rq->skb_queue, SKB_DROP_REASON_QUEUE_PURGE);
kfree(rq);
}
--
2.50.1.565.gc32cd1483b-goog
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