CVE-2024-26733

In the Linux kernel, the following vulnerability has been resolved: arp:
Prevent overflow in arp_req_get(). syzkaller reported an overflown write in
arp_req_get(). [0] When ioctl(SIOCGARP) is issued, arp_req_get() looks up
an neighbour entry and copies neigh->ha to struct arpreq.arp_ha.sa_data.
The arp_ha here is struct sockaddr, not struct sockaddr_storage, so the
sa_data buffer is just 14 bytes. In the splat below, 2 bytes are overflown
to the next int field, arp_flags. We initialise the field just after the
memcpy(), so it’s not a problem. However, when dev->addr_len is greater
than 22 (e.g. MAX_ADDR_LEN), arp_netmask is overwritten, which could be set
as htonl(0xFFFFFFFFUL) in arp_ioctl() before calling arp_req_get(). To
avoid the overflow, let’s limit the max length of memcpy(). Note that
commit b5f0de6df6dc (“net: dev: Convert sa_data to flexible array in struct
sockaddr”) just silenced syzkaller. [0]: memcpy: detected field-spanning
write (size 16) of single field “r->arp_ha.sa_data” at net/ipv4/arp.c:1128
(size 14) WARNING: CPU: 0 PID: 144638 at net/ipv4/arp.c:1128
arp_req_get+0x411/0x4a0 net/ipv4/arp.c:1128 Modules linked in: CPU: 0 PID:
144638 Comm: syz-executor.4 Not tainted 6.1.74 #31 Hardware name: QEMU
Standard PC (i440FX + PIIX, 1996), BIOS 1.16.0-debian-1.16.0-5 04/01/2014
RIP: 0010:arp_req_get+0x411/0x4a0 net/ipv4/arp.c:1128 Code: fd ff ff e8 41
42 de fb b9 0e 00 00 00 4c 89 fe 48 c7 c2 20 6d ab 87 48 c7 c7 80 6d ab 87
c6 05 25 af 72 04 01 e8 5f 8d ad fb <0f> 0b e9 6c fd ff ff e8 13 42 de fb
be 03 00 00 00 4c 89 e7 e8 a6 RSP: 0018:ffffc900050b7998 EFLAGS: 00010286
RAX: 0000000000000000 RBX: ffff88803a815000 RCX: 0000000000000000 RDX:
0000000000000000 RSI: ffffffff8641a44a RDI: 0000000000000001 RBP:
ffffc900050b7a98 R08: 0000000000000001 R09: 0000000000000000 R10:
0000000000000000 R11: 203a7970636d656d R12: ffff888039c54000 R13:
1ffff92000a16f37 R14: ffff88803a815084 R15: 0000000000000010 FS:
00007f172bf306c0(0000) GS:ffff88805aa00000(0000) knlGS:0000000000000000 CS:
0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f172b3569f0 CR3:
0000000057f12005 CR4: 0000000000770ef0 DR0: 0000000000000000 DR1:
0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6:
00000000fffe0ff0 DR7: 0000000000000400 PKRU: 55555554 Call Trace: <TASK>
arp_ioctl+0x33f/0x4b0 net/ipv4/arp.c:1261 inet_ioctl+0x314/0x3a0
net/ipv4/af_inet.c:981 sock_do_ioctl+0xdf/0x260 net/socket.c:1204
sock_ioctl+0x3ef/0x650 net/socket.c:1321 vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856
[inline] __x64_sys_ioctl+0x18e/0x220 fs/ioctl.c:856 do_syscall_x64
arch/x86/entry/common.c:51 [inline] do_syscall_64+0x37/0x90
arch/x86/entry/common.c:81 entry_SYSCALL_64_after_hwframe+0x64/0xce RIP:
0033:0x7f172b262b8d Code: 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 00 f3 0f 1e
fa 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 b8 ff ff ff f7 d8 64 89 01 48 RSP:
002b:00007f172bf300b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX:
ffffffffffffffda RBX: 00007f172b3abf80 RCX: 00007f172b262b8d RDX:
0000000020000000 RSI: 0000000000008954 RDI: 0000000000000003 RBP:
00007f172b2d3493 R08: 0000000000000000 R09: 0000000000000000 R10:
0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13:
000000000000000b R14: 00007f172b3abf80 R15: 00007f172bf10000 </TASK>