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BUG: KASAN: use-after-free in __read_once_size include/linux/compiler.h:183 [inline]
BUG: KASAN: use-after-free in bpf_fd_array_map_lookup_elem+0x440/0x4c0 kernel/bpf/arraymap.c:374
Read of size 8 at addr ffff8801cdf00778 by task syz-executor4/7103

CPU: 0 PID: 7103 Comm: syz-executor4 Not tainted 4.15.0-rc8+ #263
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 print_address_description+0x73/0x250 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report+0x25b/0x340 mm/kasan/report.c:409
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:430
 __read_once_size include/linux/compiler.h:183 [inline]
 bpf_fd_array_map_lookup_elem+0x440/0x4c0 kernel/bpf/arraymap.c:374
 map_lookup_elem+0x6b5/0xbd0 kernel/bpf/syscall.c:577
 SYSC_bpf kernel/bpf/syscall.c:1711 [inline]
 SyS_bpf+0x922/0x4400 kernel/bpf/syscall.c:1685
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452df9
RSP: 002b:00007fd28c56cc58 EFLAGS: 00000212 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007fd28c56d700 RCX: 0000000000452df9
RDX: 0000000000000018 RSI: 00000000206d1fe8 RDI: 0000000000000001
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000000
R13: 0000000000a2f7ef R14: 00007fd28c56d9c0 R15: 0000000000000000

Allocated by task 7085:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc+0xad/0xe0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x136/0x750 mm/slab.c:3610
 kmalloc include/linux/slab.h:499 [inline]
 kzalloc include/linux/slab.h:688 [inline]
 snd_ctl_open+0x1b5/0x630 sound/core/control.c:74
 snd_open+0x1fa/0x3f0 sound/core/sound.c:175
 chrdev_open+0x257/0x730 fs/char_dev.c:417
 do_dentry_open+0x667/0xd40 fs/open.c:752
 vfs_open+0x107/0x220 fs/open.c:866
 do_last fs/namei.c:3379 [inline]
 path_openat+0x1151/0x3530 fs/namei.c:3519
 do_filp_open+0x25b/0x3b0 fs/namei.c:3554
 do_sys_open+0x502/0x6d0 fs/open.c:1059
 SYSC_open fs/open.c:1077 [inline]
 SyS_open+0x2d/0x40 fs/open.c:1072
 entry_SYSCALL_64_fastpath+0x29/0xa0

Freed by task 7087:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0x71/0xc0 mm/kasan/kasan.c:524
 __cache_free mm/slab.c:3488 [inline]
 kfree+0xd6/0x260 mm/slab.c:3803
 snd_ctl_release+0x37f/0x530 sound/core/control.c:139
 __fput+0x327/0x7e0 fs/file_table.c:210
 ____fput+0x15/0x20 fs/file_table.c:244
 task_work_run+0x199/0x270 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x9bb/0x1ad0 kernel/exit.c:865
 do_group_exit+0x149/0x400 kernel/exit.c:968
 get_signal+0x73f/0x16c0 kernel/signal.c:2335
 do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath+0x490/0x550 arch/x86/entry/common.c:264
 entry_SYSCALL_64_fastpath+0x9e/0xa0

The buggy address belongs to the object at ffff8801cdf00680
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 248 bytes inside of
 256-byte region [ffff8801cdf00680, ffff8801cdf00780)
The buggy address belongs to the page:
page:ffffea000737c000 count:1 mapcount:0 mapping:ffff8801cdf00040 index:0x0
flags: 0x2fffc0000000100(slab)
raw: 02fffc0000000100 ffff8801cdf00040 0000000000000000 000000010000000c
raw: ffffea000737bd60 ffffea000737c2a0 ffff8801dac007c0 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cdf00600: 00 00 00 00 00 00 00 00 fc fc fc fc fc fc fc fc
 ffff8801cdf00680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801cdf00700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                                ^
 ffff8801cdf00780: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
 ffff8801cdf00800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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