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Subjectnet/ipv4: use-after-free in ipv4_datagram_support_cmsg
Hi,

I've got the following error report while fuzzing the kernel with syzkaller.

On commit 39da7c509acff13fc8cb12ec1bb20337c988ed36 (4.11-rc6).

Unfortunately it's not reproducible.

==================================================================
BUG: KASAN: use-after-free in ipv4_datagram_support_cmsg
net/ipv4/ip_sockglue.c:500 [inline] at addr ffff880059be0128
BUG: KASAN: use-after-free in ip_recv_error+0xb37/0xed0
net/ipv4/ip_sockglue.c:553 at addr ffff880059be0128
Read of size 4 by task syz-executor5/22308
CPU: 0 PID: 22308 Comm: syz-executor5 Not tainted 4.11.0-rc6+ #213
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:16 [inline]
dump_stack+0x292/0x398 lib/dump_stack.c:52
kasan_object_err+0x1c/0x70 mm/kasan/report.c:164
print_address_description mm/kasan/report.c:202 [inline]
kasan_report_error mm/kasan/report.c:291 [inline]
kasan_report+0x252/0x510 mm/kasan/report.c:347
__asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:367
ipv4_datagram_support_cmsg net/ipv4/ip_sockglue.c:500 [inline]
ip_recv_error+0xb37/0xed0 net/ipv4/ip_sockglue.c:553
udp_recvmsg+0xe70/0x1370 net/ipv4/udp.c:1421
inet_recvmsg+0x13e/0x600 net/ipv4/af_inet.c:793
sock_recvmsg_nosec net/socket.c:751 [inline]
sock_recvmsg+0xd7/0x110 net/socket.c:758
___sys_recvmsg+0x2f4/0x730 net/socket.c:2156
__sys_recvmsg+0x135/0x320 net/socket.c:2201
SYSC_recvmsg net/socket.c:2213 [inline]
SyS_recvmsg+0x2d/0x50 net/socket.c:2208
entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x4458d9
RSP: 002b:00007f230ab31b58 EFLAGS: 00000286 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 00000000004458d9
RDX: 0000000040002102 RSI: 0000000020edffc8 RDI: 0000000000000005
RBP: 00000000006e2d00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000286 R12: 0000000000708000
R13: 0000000000000002 R14: 0000000000708008 R15: 00007f230ab32700
Object at ffff880059be0008, in cache kmalloc-8192 size: 8192
Allocated:
PID = 16445
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:513
set_track mm/kasan/kasan.c:525 [inline]
kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:616
__kmalloc+0xa0/0x2d0 mm/slub.c:3745
kzalloc include/linux/slab.h:495 [inline]
alloc_netdev_mqs+0xbc1/0xf40 net/core/dev.c:7706
br_add_bridge+0x34/0xd0 net/bridge/br_if.c:384
br_ioctl_deviceless_stub+0x7fc/0xa30 net/bridge/br_ioctl.c:378
sock_ioctl+0x256/0x440 net/socket.c:971
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xc2
Freed:
PID = 22308
save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:59
save_stack+0x43/0xd0 mm/kasan/kasan.c:513
set_track mm/kasan/kasan.c:525 [inline]
kasan_slab_free+0x73/0xc0 mm/kasan/kasan.c:589
slab_free_hook mm/slub.c:1357 [inline]
slab_free_freelist_hook mm/slub.c:1379 [inline]
slab_free mm/slub.c:2961 [inline]
kfree+0xe8/0x2b0 mm/slub.c:3882
kvfree+0x36/0x60 mm/util.c:337
netdev_freemem+0x4c/0x60 net/core/dev.c:7658
netdev_release+0x76/0x90 net/core/net-sysfs.c:1502
device_release+0x18d/0x220 drivers/base/core.c:814
kobject_cleanup lib/kobject.c:645 [inline]
kobject_release+0xfa/0x1a0 lib/kobject.c:674
kref_put include/linux/kref.h:72 [inline]
kobject_put+0x6e/0xd0 lib/kobject.c:691
netdev_run_todo+0x6b2/0xa40 net/core/dev.c:7563
rtnl_unlock+0xe/0x10 net/core/rtnetlink.c:104
br_del_bridge+0xb6/0xe0 net/bridge/br_if.c:422
br_ioctl_deviceless_stub+0x324/0xa30 net/bridge/br_ioctl.c:380
sock_ioctl+0x256/0x440 net/socket.c:971
vfs_ioctl fs/ioctl.c:45 [inline]
do_vfs_ioctl+0x1bf/0x1780 fs/ioctl.c:685
SYSC_ioctl fs/ioctl.c:700 [inline]
SyS_ioctl+0x8f/0xc0 fs/ioctl.c:691
entry_SYSCALL_64_fastpath+0x1f/0xc2
Memory state around the buggy address:
ffff880059be0000: fc fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880059be0080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff880059be0100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff880059be0180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff880059be0200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

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