In the Linux kernel, the following vulnerability has been resolved: af_packet: Don't cast tpacket_hdr.tp_len to int in tpacket_parse_header(). syzbot reported BUG() in sock_sendmsg_nosec()

Overview

In the Linux kernel, the following vulnerability has been resolved:

af_packet: Don't cast tpacket_hdr.tp_len to int in tpacket_parse_header().

syzbot reported BUG() in sock_sendmsg_nosec(). [0]

The problem is that tpacket_parse_header() casts user-provided tpacket_hdr.tp_len, which is u32, to int.

If the length is larger than INT_MAX, the following condition in tpacket_parse_header() passes,

if (unlikely(tp_len > size_max))

and any negative value can be returned to the caller, up to sock_sendmsg_nosec().

The repro set tpacket_hdr.tp_len to 0xfffffdef, which is cast to -EIOCBQUEUED (-529), triggering BUG() in sock_sendmsg_nosec().

(uint64_t)0x200000000008 = 0xfffffdef; ... syscall(__NR_write, /fd=/r[0], /buf=/0x200000000000ul, /count=/1ul);

Let's define the local tp_len as u32 in tpacket_parse_header().

[0]: kernel BUG at net/socket.c:803! Oops: invalid opcode: 0000 [#1] SMP KASAN PTI CPU: 0 UID: 0 PID: 5628 Comm: syz-executor176 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 RIP: 0010:sock_sendmsg_nosec+0x145/0x180 net/socket.c:803 Code: 06 67 48 0f b9 3a eb 95 e8 e8 3a 22 f8 48 89 df 4c 89 f6 4c 89 e2 4d 89 fb 2e e8 32 a5 5c 16 e9 51 ff ff ff e8 cc 3a 22 f8 90 <0f> 0b e8 c4 3a 22 f8 48 83 c3 18 48 89 d8 48 c1 e8 03 42 80 3c 28 RSP: 0018:ffffc90003aefb48 EFLAGS: 00010293 RAX: ffffffff89a578d4 RBX: ffff8880764c67c0 RCX: ffff88807fb23e80 RDX: 0000000000000000 RSI: 00000000fffffdef RDI: 00000000fffffdef RBP: 00000000fffffdef R08: ffffc90003aef747 R09: 1ffff9200075dee8 R10: dffffc0000000000 R11: fffff5200075dee9 R12: 0000000000000001 R13: dffffc0000000000 R14: ffffc90003aefbc0 R15: ffffffff8aac4310 FS: 000055559101b400(0000) GS:ffff888124ce0000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000200000000210 CR3: 0000000073dca000 CR4: 00000000003526f0 Call Trace: <TASK> __sock_sendmsg net/socket.c:815 [inline] sock_write_iter+0x2de/0x3e0 net/socket.c:1266 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x612/0xba0 fs/read_write.c:687 ksys_write+0x150/0x270 fs/read_write.c:739 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f173130ecb9 Code: c0 79 93 eb d5 48 8d 7c 1d 00 eb 99 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 d8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffd67e44248 EFLAGS: 00000246 ORIG_RAX: 0000000000000001 RAX: ffffffffffffffda RBX: 0000200000000000 RCX: 00007f173130ecb9 RDX: 0000000000000001 RSI: 0000200000000000 RDI: 0000000000000003 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffd67e44388 R13: 0000000000000002 R14: 00002000000000c0 R15: 0000000000000002 </TASK>

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.