{"id":"CVE-2024-49946","summary":"ppp: do not assume bh is held in ppp_channel_bridge_input()","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nppp: do not assume bh is held in ppp_channel_bridge_input()\n\nNetworking receive path is usually handled from BH handler.\nHowever, some protocols need to acquire the socket lock, and\npackets might be stored in the socket backlog is the socket was\nowned by a user process.\n\nIn this case, release_sock(), __release_sock(), and sk_backlog_rcv()\nmight call the sk-\u003esk_backlog_rcv() handler in process context.\n\nsybot caught ppp was not considering this case in\nppp_channel_bridge_input() :\n\nWARNING: inconsistent lock state\n6.11.0-rc7-syzkaller-g5f5673607153 #0 Not tainted\n--------------------------------\ninconsistent {SOFTIRQ-ON-W} -\u003e {IN-SOFTIRQ-W} usage.\nksoftirqd/1/24 [HC0[0]:SC1[1]:HE1:SE0] takes:\n ffff0000db7f11e0 (&pch-\u003edownl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]\n ffff0000db7f11e0 (&pch-\u003edownl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]\n ffff0000db7f11e0 (&pch-\u003edownl){+.?.}-{2:2}, at: ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304\n{SOFTIRQ-ON-W} state was registered at:\n   lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759\n   __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]\n   _raw_spin_lock+0x48/0x60 kernel/locking/spinlock.c:154\n   spin_lock include/linux/spinlock.h:351 [inline]\n   ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]\n   ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304\n   pppoe_rcv_core+0xfc/0x314 drivers/net/ppp/pppoe.c:379\n   sk_backlog_rcv include/net/sock.h:1111 [inline]\n   __release_sock+0x1a8/0x3d8 net/core/sock.c:3004\n   release_sock+0x68/0x1b8 net/core/sock.c:3558\n   pppoe_sendmsg+0xc8/0x5d8 drivers/net/ppp/pppoe.c:903\n   sock_sendmsg_nosec net/socket.c:730 [inline]\n   __sock_sendmsg net/socket.c:745 [inline]\n   __sys_sendto+0x374/0x4f4 net/socket.c:2204\n   __do_sys_sendto net/socket.c:2216 [inline]\n   __se_sys_sendto net/socket.c:2212 [inline]\n   __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212\n   __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]\n   invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49\n   el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132\n   do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151\n   el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712\n   el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730\n   el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598\nirq event stamp: 282914\n hardirqs last  enabled at (282914): [\u003cffff80008b42e30c\u003e] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]\n hardirqs last  enabled at (282914): [\u003cffff80008b42e30c\u003e] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194\n hardirqs last disabled at (282913): [\u003cffff80008b42e13c\u003e] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]\n hardirqs last disabled at (282913): [\u003cffff80008b42e13c\u003e] _raw_spin_lock_irqsave+0x2c/0x7c kernel/locking/spinlock.c:162\n softirqs last  enabled at (282904): [\u003cffff8000801f8e88\u003e] softirq_handle_end kernel/softirq.c:400 [inline]\n softirqs last  enabled at (282904): [\u003cffff8000801f8e88\u003e] handle_softirqs+0xa3c/0xbfc kernel/softirq.c:582\n softirqs last disabled at (282909): [\u003cffff8000801fbdf8\u003e] run_ksoftirqd+0x70/0x158 kernel/softirq.c:928\n\nother info that might help us debug this:\n Possible unsafe locking scenario:\n\n       CPU0\n       ----\n  lock(&pch-\u003edownl);\n  \u003cInterrupt\u003e\n    lock(&pch-\u003edownl);\n\n *** DEADLOCK ***\n\n1 lock held by ksoftirqd/1/24:\n  #0: ffff80008f74dfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:325\n\nstack backtrace:\nCPU: 1 UID: 0 PID: 24 Comm: ksoftirqd/1 Not tainted 6.11.0-rc7-syzkaller-g5f5673607153 #0\nHardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024\nCall trace:\n  dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:319\n  show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326\n  __dump_sta\n---truncated---","modified":"2026-04-16T04:35:12.211602758Z","published":"2024-10-21T18:02:03.779Z","related":["SUSE-SU-2024:3983-1","SUSE-SU-2024:3984-1","SUSE-SU-2024:3985-1","SUSE-SU-2024:3986-1","SUSE-SU-2024:4318-1","SUSE-SU-2024:4364-1","SUSE-SU-2024:4387-1","SUSE-SU-2025:20163-1","SUSE-SU-2025:20164-1","SUSE-SU-2025:20246-1","SUSE-SU-2025:20247-1","USN-7276-1","USN-7277-1","openSUSE-SU-2024:14500-1","openSUSE-SU-2025:14705-1"],"database_specific":{"cna_assigner":"Linux","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/49xxx/CVE-2024-49946.json"},"references":[{"type":"WEB","url":"https://git.kernel.org/stable/c/176dd41e8c2bd997ed3d66568a3362e69ecce99b"},{"type":"WEB","url":"https://git.kernel.org/stable/c/635deca1800a68624f185dc1e04a8495b48cf185"},{"type":"WEB","url":"https://git.kernel.org/stable/c/aec7291003df78cb71fd461d7b672912bde55807"},{"type":"WEB","url":"https://git.kernel.org/stable/c/c837f8583535f094a39386308c2ccfd92c8596cd"},{"type":"WEB","url":"https://git.kernel.org/stable/c/efe9cc0f7c0279216a5522271ec675b8288602e4"},{"type":"WEB","url":"https://git.kernel.org/stable/c/f9620e2a665aa642625bd2501282bbddff556bd7"},{"type":"WEB","url":"https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/49xxx/CVE-2024-49946.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2024-49946"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"4cf476ced45d7f12df30a68e833b263e7a2202d1"},{"fixed":"176dd41e8c2bd997ed3d66568a3362e69ecce99b"},{"fixed":"635deca1800a68624f185dc1e04a8495b48cf185"},{"fixed":"f9620e2a665aa642625bd2501282bbddff556bd7"},{"fixed":"efe9cc0f7c0279216a5522271ec675b8288602e4"},{"fixed":"c837f8583535f094a39386308c2ccfd92c8596cd"},{"fixed":"aec7291003df78cb71fd461d7b672912bde55807"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-49946.json"}}],"schema_version":"1.7.5"}