CVE-2024-42106: inet_diag: Initialize pad field in struct inet_diag_req_v2

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

inetdiag: Initialize pad field in struct inetdiagreqv2

KMSAN reported uninit-value access in rawlookup() [1]. Diag for raw sockets uses the pad field in struct inetdiagreqv2 for the underlying protocol. This field corresponds to the sdiagrawprotocol field in struct inetdiagreqraw.

inetdiaggetexactcompat() converts inetdiagreq to inetdiagreqv2, but leaves the pad field uninitialized. So the issue occurs when rawlookup() accesses the sdiagrawprotocol field.

Fix this by initializing the pad field in inetdiaggetexactcompat(). Also, do the same fix in inetdiagdumpcompat() to avoid the similar issue in the future.

[1] BUG: KMSAN: uninit-value in rawlookup net/ipv4/rawdiag.c:49 [inline] BUG: KMSAN: uninit-value in rawsockget+0x657/0x800 net/ipv4/rawdiag.c:71 rawlookup net/ipv4/rawdiag.c:49 [inline] rawsockget+0x657/0x800 net/ipv4/rawdiag.c:71 rawdiagdumpone+0xa1/0x660 net/ipv4/rawdiag.c:99 inetdiagcmdexact+0x7d9/0x980 inetdiaggetexactcompat net/ipv4/inetdiag.c:1404 [inline] inetdiagrcvmsgcompat+0x469/0x530 net/ipv4/inetdiag.c:1426 sockdiagrcvmsg+0x23d/0x740 net/core/sockdiag.c:282 netlinkrcvskb+0x537/0x670 net/netlink/afnetlink.c:2564 sockdiagrcv+0x35/0x40 net/core/sockdiag.c:297 netlinkunicastkernel net/netlink/afnetlink.c:1335 [inline] netlinkunicast+0xe74/0x1240 net/netlink/afnetlink.c:1361 netlinksendmsg+0x10c6/0x1260 net/netlink/afnetlink.c:1905 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x332/0x3d0 net/socket.c:745 syssendmsg+0x7f0/0xb70 net/socket.c:2585 syssendmsg+0x271/0x3b0 net/socket.c:2639 syssendmsg net/socket.c:2668 [inline] dosyssendmsg net/socket.c:2677 [inline] sesyssendmsg net/socket.c:2675 [inline] x64syssendmsg+0x27e/0x4a0 net/socket.c:2675 x64syscall+0x135e/0x3ce0 arch/x86/include/generated/asm/syscalls64.h:47 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xd9/0x1e0 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f

Uninit was stored to memory at: rawsockget+0x650/0x800 net/ipv4/rawdiag.c:71 rawdiagdumpone+0xa1/0x660 net/ipv4/rawdiag.c:99 inetdiagcmdexact+0x7d9/0x980 inetdiaggetexactcompat net/ipv4/inetdiag.c:1404 [inline] inetdiagrcvmsgcompat+0x469/0x530 net/ipv4/inetdiag.c:1426 sockdiagrcvmsg+0x23d/0x740 net/core/sockdiag.c:282 netlinkrcvskb+0x537/0x670 net/netlink/afnetlink.c:2564 sockdiagrcv+0x35/0x40 net/core/sockdiag.c:297 netlinkunicastkernel net/netlink/afnetlink.c:1335 [inline] netlinkunicast+0xe74/0x1240 net/netlink/afnetlink.c:1361 netlinksendmsg+0x10c6/0x1260 net/netlink/afnetlink.c:1905 socksendmsgnosec net/socket.c:730 [inline] socksendmsg+0x332/0x3d0 net/socket.c:745 syssendmsg+0x7f0/0xb70 net/socket.c:2585 syssendmsg+0x271/0x3b0 net/socket.c:2639 syssendmsg net/socket.c:2668 [inline] dosyssendmsg net/socket.c:2677 [inline] sesyssendmsg net/socket.c:2675 [inline] x64syssendmsg+0x27e/0x4a0 net/socket.c:2675 x64syscall+0x135e/0x3ce0 arch/x86/include/generated/asm/syscalls64.h:47 dosyscallx64 arch/x86/entry/common.c:52 [inline] dosyscall64+0xd9/0x1e0 arch/x86/entry/common.c:83 entrySYSCALL64afterhwframe+0x77/0x7f

Local variable req.i created at: inetdiaggetexactcompat net/ipv4/inetdiag.c:1396 [inline] inetdiagrcvmsgcompat+0x2a6/0x530 net/ipv4/inetdiag.c:1426 sockdiagrcvmsg+0x23d/0x740 net/core/sockdiag.c:282

CPU: 1 PID: 8888 Comm: syz-executor.6 Not tainted 6.10.0-rc4-00217-g35bb670d65fc #32 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.3-2.fc40 04/01/2014