KASAN: use-after-free Read in bpf_test_finish

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 47350a9f ANDROID: x86_64_cuttlefish_defconfig: Enable lz4 ..
git tree: android-4.14
console output: https://syzkaller.appspot.com/x/log.txt?x=13e8c492400000
kernel config: https://syzkaller.appspot.com/x/.config?x=10d236078f3378a3
dashboard link: https://syzkaller.appspot.com/bug?extid=0133ed9afa71a766cd03
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1537e87c400000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=173aa13e400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+0133ed...@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
urandom_read: 1 callbacks suppressed
random: sshd: uninitialized urandom read (32 bytes read)
==================================================================
BUG: KASAN: use-after-free in _copy_to_user+0x9a/0xc0 lib/usercopy.c:27
Read of size 1033 at addr ffff8801cbbffffc by task syz-executor113/1961

CPU: 0 PID: 1961 Comm: syz-executor113 Not tainted 4.14.67+ #1
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0xb9/0x11b lib/dump_stack.c:53
print_address_description+0x60/0x22b mm/kasan/report.c:252
kasan_report_error mm/kasan/report.c:351 [inline]
kasan_report.cold.6+0x11b/0x2dd mm/kasan/report.c:409
_copy_to_user+0x9a/0xc0 lib/usercopy.c:27
copy_to_user include/linux/uaccess.h:155 [inline]
bpf_test_finish.isra.0+0xc8/0x190 net/bpf/test_run.c:59
bpf_prog_test_run_skb+0x4d0/0x8c0 net/bpf/test_run.c:144
bpf_prog_test_run kernel/bpf/syscall.c:1330 [inline]
SYSC_bpf kernel/bpf/syscall.c:1602 [inline]
SyS_bpf+0x79d/0x3640 kernel/bpf/syscall.c:1547
do_syscall_64+0x19b/0x4b0 arch/x86/entry/common.c:289
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x440259
RSP: 002b:00007ffe76de4bf8 EFLAGS: 00000213 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 0000000000440259
RDX: 0000000000000028 RSI: 0000000020000300 RDI: 000000000000000a
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000213 R12: 0000000000401ae0
R13: 0000000000401b70 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00072effc0 count:0 mapcount:0 mapping: (null) index:0x1
flags: 0x4000000000000000()
raw: 4000000000000000 0000000000000000 0000000000000001 00000000ffffffff
raw: dead000000000100 dead000000000200 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8801cbbffe80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
ffff8801cbbfff00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
> ffff8801cbbfff80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
^
ffff8801cbc00000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffff8801cbc00080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================


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