From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 132D8384CED; Sat, 17 Oct 2026 16:28:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792254494; cv=none; b=QYIerj1YAEtenT2SDJun+RcdrRVITwbkOSB2n7rB5pXCX7ByyJCfu4QJ9jjOcxjvYrn7CXumzuKS/UXltPzCfa7cBJKuGXoq6tGDYDPJH0PZI0BoocIpogX8X9ffj5CBouP6ia3tCoB4tztcG2wO1c+quk1w8WVyh2oJSvDOxBw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792254494; c=relaxed/simple; bh=rPUf9+HseMh44gbvCDqTIv8qTJQPZAU0e/zQ/uKQQO8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=YvrtLqtspFX8bAEm7WbbW5ngPHU0MvMZmWrZPBHKK8ahpsc+DfPnCKVlAIs70o6xtJ8Rs9jWYZu9rNOzdZvruEj5fx8uTiRvLxxMQJcwBsKLixHlJh1Xzq1ZG/HS8ScAR0pIP2zPl6xsVHooc5MyZxQDbk4OILEEucI0Vo/tqdA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=gNy3XCxI; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="gNy3XCxI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 664B41F000C4; Sat, 17 Oct 2026 16:28:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1792254493; bh=NdloQ73GLrTF1LUBhXqKyIjqc4g9o8s4JJapXt/3Gwk=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=gNy3XCxIhp1qLCwZidb8f5SOHjhz95YHDdc5fEL+KIpGeF0PT0gpEd8YdQpkwEJra KIwBhNVvXL06DdDF184T2o6mSQsWkpMvvycgwpwphyRjuNn59y8psp11px42CVTAye S1PLffSCgQgdZIJry2qkz1hafASyWbyBeLLPHtdo= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+9307c991a6d07ce6e6d8@syzkaller.appspotmail.com, Jiayuan Chen , Jakub Sitnicki , Emil Tsalapatis , Kuniyuki Iwashima , Alexei Starovoitov , Sasha Levin Subject: [PATCH 6.12 463/869] sockmap: Fix use-after-free in udp_bpf_recvmsg() Date: Sat, 17 Oct 2026 17:55:04 +0200 Message-ID: <20261017160049.002798719@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261017160036.979869304@linuxfoundation.org> References: <20261017160036.979869304@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: 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 c010995b29c8939c6aa69e3cb26f8dbee163d156 ] syzbot reported use-after-free of struct sk_msg in sk_msg_recvmsg(). [0] sk_msg_recvmsg() peeks sk_msg from psock->ingress_msg under a lock, but its processing is lockless. Thus, sk_msg_recvmsg() must be serialised by callers, otherwise multiple threads could touch the same sk_msg. For example, TCP uses lock_sock(), and AF_UNIX uses unix_sk(sk)->iolock. Initially, udp_bpf_recvmsg() had used lock_sock(), but the cited commit removed it. Let's serialise sk_msg_recvmsg() with lock_sock() in udp_bpf_recvmsg(). Note that holding spin_lock_bh(&sk->sk_receive_queue.lock) is not an option due to copy_page_to_iter() in sk_msg_recvmsg(). [0]: BUG: KASAN: slab-use-after-free in sk_msg_recvmsg+0xb54/0xc30 net/core/skmsg.c:428 Read of size 4 at addr ffff88814cdcf000 by task syz.0.24/6020 CPU: 1 UID: 0 PID: 6020 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Compute Engine/Google Compute Engine, BIOS Google 01/13/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xba/0x230 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 sk_msg_recvmsg+0xb54/0xc30 net/core/skmsg.c:428 udp_bpf_recvmsg+0x4bd/0xe00 net/ipv4/udp_bpf.c:84 inet_recvmsg+0x260/0x270 net/ipv4/af_inet.c:891 sock_recvmsg_nosec net/socket.c:1078 [inline] sock_recvmsg+0x1a8/0x270 net/socket.c:1100 ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2812 ___sys_recvmsg+0x215/0x590 net/socket.c:2854 do_recvmmsg+0x334/0x800 net/socket.c:2949 __sys_recvmmsg net/socket.c:3023 [inline] __do_sys_recvmmsg net/socket.c:3046 [inline] __se_sys_recvmmsg net/socket.c:3039 [inline] __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3039 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7fb319f9aeb9 Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 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 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fb31ad97028 EFLAGS: 00000246 ORIG_RAX: 000000000000012b RAX: ffffffffffffffda RBX: 00007fb31a216090 RCX: 00007fb319f9aeb9 RDX: 0000000000000001 RSI: 0000200000000400 RDI: 0000000000000004 RBP: 00007fb31a008c1f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000040000021 R11: 0000000000000246 R12: 0000000000000000 R13: 00007fb31a216128 R14: 00007fb31a216090 R15: 00007ffe21dd0a98 Allocated by task 6019: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 poison_kmalloc_redzone mm/kasan/common.c:398 [inline] __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:415 kasan_kmalloc include/linux/kasan.h:263 [inline] __kmalloc_cache_noprof+0x3d1/0x6e0 mm/slub.c:5780 kmalloc_noprof include/linux/slab.h:957 [inline] kzalloc_noprof include/linux/slab.h:1094 [inline] alloc_sk_msg net/core/skmsg.c:510 [inline] sk_psock_skb_ingress_self+0x60/0x350 net/core/skmsg.c:612 sk_psock_verdict_apply net/core/skmsg.c:1038 [inline] sk_psock_verdict_recv+0x7d9/0x8d0 net/core/skmsg.c:1236 udp_read_skb+0x73e/0x7e0 net/ipv4/udp.c:2045 sk_psock_verdict_data_ready+0x12d/0x550 net/core/skmsg.c:1257 __udp_enqueue_schedule_skb+0xc54/0x10b0 net/ipv4/udp.c:1789 __udp_queue_rcv_skb net/ipv4/udp.c:2346 [inline] udp_queue_rcv_one_skb+0xac5/0x19c0 net/ipv4/udp.c:2475 __udp4_lib_mcast_deliver+0xc06/0xcf0 net/ipv4/udp.c:2585 __udp4_lib_rcv+0x10f6/0x2620 net/ipv4/udp.c:2724 ip_protocol_deliver_rcu+0x282/0x440 net/ipv4/ip_input.c:207 ip_local_deliver_finish+0x3bb/0x6f0 net/ipv4/ip_input.c:241 NF_HOOK+0x336/0x3c0 include/linux/netfilter.h:318 dst_input include/net/dst.h:474 [inline] ip_sublist_rcv_finish+0x221/0x2a0 net/ipv4/ip_input.c:584 ip_list_rcv_finish net/ipv4/ip_input.c:628 [inline] ip_sublist_rcv+0x5c6/0xa70 net/ipv4/ip_input.c:644 ip_list_rcv+0x3f1/0x450 net/ipv4/ip_input.c:678 __netif_receive_skb_list_ptype net/core/dev.c:6195 [inline] __netif_receive_skb_list_core+0x7e5/0x810 net/core/dev.c:6242 __netif_receive_skb_list net/core/dev.c:6294 [inline] netif_receive_skb_list_internal+0x995/0xcf0 net/core/dev.c:6385 netif_receive_skb_list+0x54/0x410 net/core/dev.c:6437 xdp_recv_frames net/bpf/test_run.c:269 [inline] xdp_test_run_batch net/bpf/test_run.c:350 [inline] bpf_test_run_xdp_live+0x1946/0x1cf0 net/bpf/test_run.c:379 bpf_prog_test_run_xdp+0x81c/0x1160 net/bpf/test_run.c:1396 bpf_prog_test_run+0x2c7/0x340 kernel/bpf/syscall.c:4703 __sys_bpf+0x5cb/0x920 kernel/bpf/syscall.c:6182 __do_sys_bpf kernel/bpf/syscall.c:6274 [inline] __se_sys_bpf kernel/bpf/syscall.c:6272 [inline] __x64_sys_bpf+0x7c/0x90 kernel/bpf/syscall.c:6272 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 6021: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free mm/slub.c:6674 [inline] kfree+0x1be/0x650 mm/slub.c:6882 kfree_sk_msg include/linux/skmsg.h:385 [inline] sk_msg_recvmsg+0xaa8/0xc30 net/core/skmsg.c:483 udp_bpf_recvmsg+0x4bd/0xe00 net/ipv4/udp_bpf.c:84 inet_recvmsg+0x260/0x270 net/ipv4/af_inet.c:891 sock_recvmsg_nosec net/socket.c:1078 [inline] sock_recvmsg+0x1a8/0x270 net/socket.c:1100 ____sys_recvmsg+0x1e6/0x4a0 net/socket.c:2812 ___sys_recvmsg+0x215/0x590 net/socket.c:2854 do_recvmmsg+0x334/0x800 net/socket.c:2949 __sys_recvmmsg net/socket.c:3023 [inline] __do_sys_recvmmsg net/socket.c:3046 [inline] __se_sys_recvmmsg net/socket.c:3039 [inline] __x64_sys_recvmmsg+0x198/0x250 net/socket.c:3039 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xe2/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Fixes: 9f2470fbc4cb ("skmsg: Improve udp_bpf_recvmsg() accuracy") Reported-by: syzbot+9307c991a6d07ce6e6d8@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/69922ac9.a70a0220.2c38d7.00e0.GAE@google.com/ Reviewed-by: Jiayuan Chen Reviewed-by: Jakub Sitnicki Reviewed-by: Emil Tsalapatis Signed-off-by: Kuniyuki Iwashima Signed-off-by: Jiayuan Chen Link: https://lore.kernel.org/r/20260615021959.140010-5-jiayuan.chen@linux.dev Signed-off-by: Alexei Starovoitov Signed-off-by: Sasha Levin --- net/ipv4/udp_bpf.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/ipv4/udp_bpf.c b/net/ipv4/udp_bpf.c index 779a3a03762f1..b07774034a910 100644 --- a/net/ipv4/udp_bpf.c +++ b/net/ipv4/udp_bpf.c @@ -52,7 +52,9 @@ static int udp_msg_wait_data(struct sock *sk, struct sk_psock *psock, sk_set_bit(SOCKWQ_ASYNC_WAITDATA, sk); ret = udp_msg_has_data(sk, psock); if (!ret) { + release_sock(sk); wait_woken(&wait, TASK_INTERRUPTIBLE, timeo); + lock_sock(sk); ret = udp_msg_has_data(sk, psock); } sk_clear_bit(SOCKWQ_ASYNC_WAITDATA, sk); @@ -81,6 +83,7 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, goto out; } + lock_sock(sk); msg_bytes_ready: copied = sk_msg_recvmsg(sk, psock, msg, len, flags); if (!copied) { @@ -92,11 +95,17 @@ static int udp_bpf_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, if (data) { if (psock_has_data(psock)) goto msg_bytes_ready; + + release_sock(sk); + ret = sk_udp_recvmsg(sk, msg, len, flags, addr_len); goto out; } copied = -EAGAIN; } + + release_sock(sk); + ret = copied; out: sk_psock_put(sk, psock); -- 2.53.0