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CVE-2024-49946

Description

In the Linux kernel, the following vulnerability has been resolved:ppp: do not assume bh is held in ppp_channel_bridge_input()Networking receive path is usually handled from BH handler.However, some protocols need to acquire the socket lock, andpackets might be stored in the socket backlog is the socket wasowned by a user process.In this case, release_sock(), __release_sock(), and sk_backlog_rcv()might call the sk->sk_backlog_rcv() handler in process context.sybot caught ppp was not considering this case inppp_channel_bridge_input() :WARNING: inconsistent lock state6.11.0-rc7-syzkaller-g5f5673607153 #0 Not tainted--------------------------------inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.ksoftirqd/1/24 [HC0[0]:SC1[1]:HE1:SE0] takes: ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline] ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline] ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304{SOFTIRQ-ON-W} state was registered at: lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline] _raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154 spin_lock include/linux/spinlock.h:351 [inline] ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline] ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304 pppoe_rcv_core+0xfc/0x314 drivers/net/ppp/pppoe.c:379 sk_backlog_rcv include/net/sock.h:1111 [inline] __release_sock+0x1a8/0x3d8 net/core/sock.c:3004 release_sock+0x68/0x1b8 net/core/sock.c:3558 pppoe_sendmsg+0xc8/0x5d8 drivers/net/ppp/pppoe.c:903 sock_sendmsg_nosec net/socket.c:730 [inline] __sock_sendmsg net/socket.c:745 [inline] __sys_sendto+0x374/0x4f4 net/socket.c:2204 __do_sys_sendto net/socket.c:2216 [inline] __se_sys_sendto net/socket.c:2212 [inline] __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712 el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598irq event stamp: 282914 hardirqs last enabled at (282914): [] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] hardirqs last enabled at (282914): [] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194 hardirqs last disabled at (282913): [] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline] hardirqs last disabled at (282913): [] _raw_spin_lock_irqsave+0x2c/0x7c kernel/locking/spinlock.c:162 softirqs last enabled at (282904): [] softirq_handle_end kernel/softirq.c:400 [inline] softirqs last enabled at (282904): [] handle_softirqs+0xa3c/0xbfc kernel/softirq.c:582 softirqs last disabled at (282909): [] run_ksoftirqd+0x70/0x158 kernel/softirq.c:928other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&pch->downl); lock(&pch->downl); *** DEADLOCK ***1 lock held by ksoftirqd/1/24: #0: ffff80008f74dfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:325stack backtrace:CPU: 1 UID: 0 PID: 24 Comm: ksoftirqd/1 Not tainted 6.11.0-rc7-syzkaller-g5f5673607153 #0Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024Call trace: dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:319 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326 __dump_sta---truncated---

CVE-2024-49946

Description

POC

Reference

Github