CVE-2024-49946

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