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Date: Fri, 13 Nov 2026 10:50:50 -0500 Message-ID: <20261113153828.405550642@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261113153811.177190860@linuxfoundation.org> References: <20261113153811.177190860@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kuniyuki Iwashima [ Upstream commit 019c892e46544af0ae94ec833f79aa903c837666 ] Yi Lai reported RCU splat in reg_vif_xmit() below. [0] When CONFIG_IP_MROUTE_MULTIPLE_TABLES=n, ipmr_fib_lookup() uses rcu_dereference() without explicit rcu_read_lock(). Although rcu_read_lock_bh() is already held by the caller __dev_queue_xmit(), lockdep requires explicit rcu_read_lock() for rcu_dereference(). Let's move up rcu_read_lock() in reg_vif_xmit() to cover ipmr_fib_lookup(). [0]: WARNING: suspicious RCU usage 7.1.0-rc2-next-20260504-9d0d467c3572 #1 Not tainted ----------------------------- net/ipv4/ipmr.c:329 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 2 locks held by syz.2.17/1779: #0: ffffffff87896440 (rcu_read_lock_bh){....}-{1:3}, at: local_bh_disable include/linux/bottom_half.h:20 [inline] #0: ffffffff87896440 (rcu_read_lock_bh){....}-{1:3}, at: rcu_read_lock_bh include/linux/rcupdate.h:891 [inline] #0: ffffffff87896440 (rcu_read_lock_bh){....}-{1:3}, at: __dev_queue_xmit+0x239/0x4140 net/core/dev.c:4792 #1: ffff88801a199d18 (_xmit_PIMREG#2){+...}-{3:3}, at: spin_lock include/linux/spinlock.h:342 [inline] #1: ffff88801a199d18 (_xmit_PIMREG#2){+...}-{3:3}, at: __netif_tx_lock include/linux/netdevice.h:4795 [inline] #1: ffff88801a199d18 (_xmit_PIMREG#2){+...}-{3:3}, at: __dev_queue_xmit+0x1d5d/0x4140 net/core/dev.c:4865 stack backtrace: CPU: 1 UID: 0 PID: 1779 Comm: syz.2.17 Not tainted 7.1.0-rc2-next-20260504-9d0d467c3572 #1 PREEMPT(lazy) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x121/0x150 lib/dump_stack.c:120 dump_stack+0x19/0x20 lib/dump_stack.c:129 lockdep_rcu_suspicious+0x15b/0x1f0 kernel/locking/lockdep.c:6878 ipmr_fib_lookup net/ipv4/ipmr.c:329 [inline] reg_vif_xmit+0x2ee/0x3c0 net/ipv4/ipmr.c:540 __netdev_start_xmit include/linux/netdevice.h:5382 [inline] netdev_start_xmit include/linux/netdevice.h:5391 [inline] xmit_one net/core/dev.c:3889 [inline] dev_hard_start_xmit+0x170/0x700 net/core/dev.c:3905 __dev_queue_xmit+0x1df1/0x4140 net/core/dev.c:4871 dev_queue_xmit include/linux/netdevice.h:3423 [inline] packet_xmit+0x252/0x370 net/packet/af_packet.c:276 packet_snd net/packet/af_packet.c:3082 [inline] packet_sendmsg+0x39ad/0x5650 net/packet/af_packet.c:3114 sock_sendmsg_nosec net/socket.c:797 [inline] __sock_sendmsg net/socket.c:812 [inline] ____sys_sendmsg+0xa21/0xba0 net/socket.c:2716 ___sys_sendmsg+0x121/0x1c0 net/socket.c:2770 __sys_sendmsg+0x177/0x220 net/socket.c:2802 __do_sys_sendmsg net/socket.c:2807 [inline] __se_sys_sendmsg net/socket.c:2805 [inline] __x64_sys_sendmsg+0x80/0xc0 net/socket.c:2805 x64_sys_call+0x1d9c/0x21c0 arch/x86/include/generated/asm/syscalls_64.h:47 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xc1/0x1020 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x76/0x7e RIP: 0033:0x7f37e563ee5d Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d 93 af 1b 00 f7 d8 64 89 01 48 RSP: 002b:00007ffe5caa7fa8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00000000005c5fa0 RCX: 00007f37e563ee5d RDX: 0000000000000000 RSI: 00002000000012c0 RDI: 0000000000000004 RBP: 00000000005c5fa0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00000000005c5fac R15: 00000000005c5fa0 Fixes: b3b6babf4751 ("ipmr: Free mr_table after RCU grace period.") Reported-by: syzkaller Reported-by: Yi Lai Closes: https://lore.kernel.org/netdev/afrY34dLXNUboevf@ly-workstation/ Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260506065955.1695753-1-kuniyu@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: aa1799e93f5e ("ipmr, ip6mr: validate packets injected into the register vif on xmit") Signed-off-by: Sasha Levin --- net/ipv4/ipmr.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c index 3b58e8e88ad25..6ebbd83b01306 100644 --- a/net/ipv4/ipmr.c +++ b/net/ipv4/ipmr.c @@ -513,15 +513,16 @@ static netdev_tx_t reg_vif_xmit(struct sk_buff *skb, struct net_device *dev) }; int err; + rcu_read_lock(); err = ipmr_fib_lookup(net, &fl4, &mrt); if (err < 0) { + rcu_read_unlock(); kfree_skb(skb); return err; } DEV_STATS_ADD(dev, tx_bytes, skb->len); DEV_STATS_INC(dev, tx_packets); - rcu_read_lock(); /* Pairs with WRITE_ONCE() in vif_add() and vif_delete() */ ipmr_cache_report(mrt, skb, READ_ONCE(mrt->mroute_reg_vif_num), -- 2.53.0