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>