Re: [syzbot] KASAN: vmalloc-out-of-bounds Write in ringbuf_map_alloc

syzbot
2022-02-02T12:11:32Z

syzbot has found a reproducer for the following issue on:

HEAD commit: 6abab1b81b65 Add linux-next specific files for 20220202
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=13f4b900700000
kernel config: https://syzkaller.appspot.com/x/.config?x=b8d8750556896349
dashboard link: https://syzkaller.appspot.com/bug?extid=5ad567a418794b9b5983
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1450d9f0700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=130ef35bb00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5ad567a418794b9b5983@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: vmalloc-out-of-bounds in bpf_ringbuf_area_alloc kernel/bpf/ringbuf.c:110 [inline]
BUG: KASAN: vmalloc-out-of-bounds in bpf_ringbuf_alloc kernel/bpf/ringbuf.c:133 [inline]
BUG: KASAN: vmalloc-out-of-bounds in ringbuf_map_alloc kernel/bpf/ringbuf.c:172 [inline]
BUG: KASAN: vmalloc-out-of-bounds in ringbuf_map_alloc+0x725/0x7b0 kernel/bpf/ringbuf.c:148
Write of size 8 at addr ffffc9000c7a9078 by task syz-executor070/3595

CPU: 0 PID: 3595 Comm: syz-executor070 Not tainted 5.17.0-rc2-next-20220202-syzkaller #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/0x3e0 mm/kasan/report.c:255
__kasan_report mm/kasan/report.c:442 [inline]
kasan_report.cold+0x83/0xdf mm/kasan/report.c:459
bpf_ringbuf_area_alloc kernel/bpf/ringbuf.c:110 [inline]
bpf_ringbuf_alloc kernel/bpf/ringbuf.c:133 [inline]
ringbuf_map_alloc kernel/bpf/ringbuf.c:172 [inline]
ringbuf_map_alloc+0x725/0x7b0 kernel/bpf/ringbuf.c:148
find_and_alloc_map kernel/bpf/syscall.c:128 [inline]
map_create kernel/bpf/syscall.c:863 [inline]
__sys_bpf+0xc0f/0x5f10 kernel/bpf/syscall.c:4622
__do_sys_bpf kernel/bpf/syscall.c:4744 [inline]
__se_sys_bpf kernel/bpf/syscall.c:4742 [inline]
__x64_sys_bpf+0x75/0xb0 kernel/bpf/syscall.c:4742
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: 0033:0x7f26ddd0a029
Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 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:00007fff911fde88 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f26ddd0a029
RDX: 0000000000000048 RSI: 0000000020000280 RDI: 0000000000000000
RBP: 00007f26ddcce010 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 00007f26ddcce0a0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>

Memory state around the buggy address:
ffffc9000c7a8f00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc9000c7a8f80: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
>ffffc9000c7a9000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^
ffffc9000c7a9080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc9000c7a9100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================