CVE-2022-48839

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

net/packet: fix slab-out-of-bounds access in packet_recvmsg()

syzbot found that when an AF_PACKET socket is using PACKET_COPY_THRESH

and mmap operations, tpacket_rcv() is queueing skbs with

garbage in skb->cb[], triggering a too big copy [1]

Presumably, users of af_packet using mmap() already gets correct

metadata from the mapped buffer, we can simply make sure

to clear 12 bytes that might be copied to user space later.

BUG: KASAN: stack-out-of-bounds in memcpy include/linux/fortify-string.h:225 [inline]

BUG: KASAN: stack-out-of-bounds in packet_recvmsg+0x56c/0x1150 net/packet/af_packet.c:3489

Write of size 165 at addr ffffc9000385fb78 by task syz-executor233/3631

CPU: 0 PID: 3631 Comm: syz-executor233 Not tainted 5.17.0-rc7-syzkaller-02396-g0b3660695e80 #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

Call Trace:

<TASK>

__dump_stack lib/dump_stack.c:88 [inline]

dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106

print_address_description.constprop.0.cold+0xf/0x336 mm/kasan/report.c:255

__kasan_report mm/kasan/report.c:442 [inline]

kasan_report.cold+0x83/0xdf mm/kasan/report.c:459

check_region_inline mm/kasan/generic.c:183 [inline]

kasan_check_range+0x13d/0x180 mm/kasan/generic.c:189

memcpy+0x39/0x60 mm/kasan/shadow.c:66

memcpy include/linux/fortify-string.h:225 [inline]

packet_recvmsg+0x56c/0x1150 net/packet/af_packet.c:3489

sock_recvmsg_nosec net/socket.c:948 [inline]

sock_recvmsg net/socket.c:966 [inline]

sock_recvmsg net/socket.c:962 [inline]

____sys_recvmsg+0x2c4/0x600 net/socket.c:2632

___sys_recvmsg+0x127/0x200 net/socket.c:2674

__sys_recvmsg+0xe2/0x1a0 net/socket.c:2704

do_syscall_x64 arch/x86/entry/common.c:50 [inline]

do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80

entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x7fdfd5954c29

Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 41 15 00 00 90 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 c0 ff ff ff f7 d8 64 89 01 48

RSP: 002b:00007ffcf8e71e48 EFLAGS: 00000246 ORIG_RAX: 000000000000002f

RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fdfd5954c29

RDX: 0000000000000000 RSI: 0000000020000500 RDI: 0000000000000005

RBP: 0000000000000000 R08: 000000000000000d R09: 000000000000000d

R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffcf8e71e60

R13: 00000000000f4240 R14: 000000000000c1ff R15: 00007ffcf8e71e54

</TASK>

addr ffffc9000385fb78 is located in stack of task syz-executor233/3631 at offset 32 in frame:

____sys_recvmsg+0x0/0x600 include/linux/uio.h:246

this frame has 1 object:

[32, 160) 'addr'

Memory state around the buggy address:

ffffc9000385fa80: 00 04 f3 f3 f3 f3 f3 00 00 00 00 00 00 00 00 00

ffffc9000385fb00: 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00

>ffffc9000385fb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f3

^

ffffc9000385fc00: f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 f1

ffffc9000385fc80: f1 f1 f1 00 f2 f2 f2 00 f2 f2 f2 00 00 00 00 00

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