Subject: KASAN: slab-out-of-bounds Write in xt_compat_target_from_user

From: syzbot <[email-masked]>
Date: Mon, 17 Aug 2020 10:51:21 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    4b6c093e Merge tag 'block-5.9-2020-08-14' of git://git.ker..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14741412900000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a98b778f5fca0653
dashboard link: https://syzkaller.appspot.com/bug?extid=cfc0247ac173f597aaaa
compiler:       gcc (GCC) 10.1.0-syz 20200507
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1283a731900000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10dd10ce900000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

==================================================================
BUG: KASAN: slab-out-of-bounds in memset include/linux/string.h:391 [inline]
BUG: KASAN: slab-out-of-bounds in xt_compat_target_from_user+0x232/0x470 net/netfilter/x_tables.c:1129
Write of size 4 at addr ffff88809c971ba1 by task syz-executor166/6841

CPU: 1 PID: 6841 Comm: syz-executor166 Not tainted 5.8.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 check_memory_region_inline mm/kasan/generic.c:186 [inline]
 check_memory_region+0x13d/0x180 mm/kasan/generic.c:192
 memset+0x20/0x40 mm/kasan/common.c:84
 memset include/linux/string.h:391 [inline]
 xt_compat_target_from_user+0x232/0x470 net/netfilter/x_tables.c:1129
 compat_copy_entry_from_user net/ipv6/netfilter/ip6_tables.c:1392 [inline]
 translate_compat_table+0x1011/0x1720 net/ipv6/netfilter/ip6_tables.c:1455
 compat_do_replace.constprop.0+0x1f0/0x470 net/ipv6/netfilter/ip6_tables.c:1526
 do_ip6t_set_ctl+0x5b0/0xb73 net/ipv6/netfilter/ip6_tables.c:1633
 nf_setsockopt+0x83/0xe0 net/netfilter/nf_sockopt.c:101
 ipv6_setsockopt+0x122/0x180 net/ipv6/ipv6_sockglue.c:1008
 udpv6_setsockopt+0x76/0xc0 net/ipv6/udp.c:1626
 __sys_setsockopt+0x2db/0x610 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2143 [inline]
 __se_sys_setsockopt net/socket.c:2140 [inline]
 __ia32_sys_setsockopt+0xb9/0x150 net/socket.c:2140
 do_syscall_32_irqs_on arch/x86/entry/common.c:84 [inline]
 __do_fast_syscall_32+0x57/0x80 arch/x86/entry/common.c:126
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:149
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c
RIP: 0023:0xf7fd3549
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7fad18c EFLAGS: 00000292 ORIG_RAX: 000000000000016e
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000000000029
RDX: 0000000000000040 RSI: 0000000020000a00 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6841:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmalloc_node include/linux/slab.h:577 [inline]
 kvmalloc_node+0x61/0xf0 mm/util.c:574
 kvmalloc include/linux/mm.h:750 [inline]
 xt_alloc_table_info+0x3c/0xa0 net/netfilter/x_tables.c:1176
 translate_compat_table+0xc50/0x1720 net/ipv6/netfilter/ip6_tables.c:1442
 compat_do_replace.constprop.0+0x1f0/0x470 net/ipv6/netfilter/ip6_tables.c:1526
 do_ip6t_set_ctl+0x5b0/0xb73 net/ipv6/netfilter/ip6_tables.c:1633
 nf_setsockopt+0x83/0xe0 net/netfilter/nf_sockopt.c:101
 ipv6_setsockopt+0x122/0x180 net/ipv6/ipv6_sockglue.c:1008
 udpv6_setsockopt+0x76/0xc0 net/ipv6/udp.c:1626
 __sys_setsockopt+0x2db/0x610 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2143 [inline]
 __se_sys_setsockopt net/socket.c:2140 [inline]
 __ia32_sys_setsockopt+0xb9/0x150 net/socket.c:2140
 do_syscall_32_irqs_on arch/x86/entry/common.c:84 [inline]
 __do_fast_syscall_32+0x57/0x80 arch/x86/entry/common.c:126
 do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:149
 entry_SYSENTER_compat_after_hwframe+0x4d/0x5c

The buggy address belongs to the object at ffff88809c971800
 which belongs to the cache kmalloc-1k of size 1024
The buggy address is located 929 bytes inside of
 1024-byte region [ffff88809c971800, ffff88809c971c00)
The buggy address belongs to the page:
page:00000000d9974640 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88809c971000 pfn:0x9c971
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea000269a448 ffffea00027cc908 ffff8880aa040700
raw: ffff88809c971000 ffff88809c971000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff88809c971a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff88809c971b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff88809c971b80: 00 00 fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                               ^
 ffff88809c971c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88809c971c80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

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