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SubjectKASAN: use-after-free Read in bpf_get_prog_name
From
Hello,

syzbot found the following crash on:

HEAD commit: 192f0f8e Merge tag 'powerpc-5.3-1' of git://git.kernel.org..
git tree: bpf-next
console output: https://syzkaller.appspot.com/x/log.txt?x=170afe64600000
kernel config: https://syzkaller.appspot.com/x/.config?x=87305c3ca9c25c70
dashboard link: https://syzkaller.appspot.com/bug?extid=4d5cdc96ead2e74e7f90
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4d5cdc96ead2e74e7f90@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: use-after-free in string_nocheck+0x219/0x240 lib/vsprintf.c:605
Read of size 1 at addr ffff88809fee2d70 by task syz-executor.1/30647

CPU: 1 PID: 30647 Comm: syz-executor.1 Not tainted 5.2.0+ #41
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+0x172/0x1f0 lib/dump_stack.c:113
print_address_description.cold+0xd4/0x306 mm/kasan/report.c:351
__kasan_report.cold+0x1b/0x36 mm/kasan/report.c:482
kasan_report+0x12/0x20 mm/kasan/common.c:612
__asan_report_load1_noabort+0x14/0x20 mm/kasan/generic_report.c:129
string_nocheck+0x219/0x240 lib/vsprintf.c:605
string+0xed/0x100 lib/vsprintf.c:668
vsnprintf+0x97b/0x19a0 lib/vsprintf.c:2503
snprintf+0xbb/0xf0 lib/vsprintf.c:2636
bpf_get_prog_name+0x159/0x360 kernel/bpf/core.c:570
perf_event_bpf_emit_ksymbols+0x284/0x390 kernel/events/core.c:7883
perf_event_bpf_event+0x253/0x290 kernel/events/core.c:7914
bpf_prog_load+0x102a/0x1670 kernel/bpf/syscall.c:1723
__do_sys_bpf+0xa46/0x42f0 kernel/bpf/syscall.c:2849
__se_sys_bpf kernel/bpf/syscall.c:2808 [inline]
__x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:2808
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f8c78cf3c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 0000000000000070 RSI: 0000000020000240 RDI: 0000000000000005
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f8c78cf46d4
R13: 00000000004bfc7c R14: 00000000004d16d8 R15: 00000000ffffffff

Allocated by task 30647:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_kmalloc mm/kasan/common.c:487 [inline]
__kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:460
kasan_kmalloc+0x9/0x10 mm/kasan/common.c:501
kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3550
kmalloc include/linux/slab.h:552 [inline]
kzalloc include/linux/slab.h:748 [inline]
bpf_prog_alloc_no_stats+0xe6/0x2b0 kernel/bpf/core.c:88
bpf_prog_alloc+0x31/0x230 kernel/bpf/core.c:110
bpf_prog_load+0x400/0x1670 kernel/bpf/syscall.c:1652
__do_sys_bpf+0xa46/0x42f0 kernel/bpf/syscall.c:2849
__se_sys_bpf kernel/bpf/syscall.c:2808 [inline]
__x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:2808
do_syscall_64+0xfd/0x6a0 arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 12:
save_stack+0x23/0x90 mm/kasan/common.c:69
set_track mm/kasan/common.c:77 [inline]
__kasan_slab_free+0x102/0x150 mm/kasan/common.c:449
kasan_slab_free+0xe/0x10 mm/kasan/common.c:457
__cache_free mm/slab.c:3425 [inline]
kfree+0x10a/0x2c0 mm/slab.c:3756
__bpf_prog_free+0x87/0xc0 kernel/bpf/core.c:258
bpf_jit_free+0x64/0x1b0
bpf_prog_free_deferred+0x27a/0x350 kernel/bpf/core.c:1982
process_one_work+0x9af/0x1740 kernel/workqueue.c:2269
worker_thread+0x98/0xe40 kernel/workqueue.c:2415
kthread+0x361/0x430 kernel/kthread.c:255
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:352

The buggy address belongs to the object at ffff88809fee2cc0
which belongs to the cache kmalloc-512 of size 512
The buggy address is located 176 bytes inside of
512-byte region [ffff88809fee2cc0, ffff88809fee2ec0)
The buggy address belongs to the page:
page:ffffea00027fb880 refcount:1 mapcount:0 mapping:ffff8880aa400a80
index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002709008 ffffea000246e348 ffff8880aa400a80
raw: 0000000000000000 ffff88809fee2040 0000000100000006 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff88809fee2c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88809fee2c80: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> ffff88809fee2d00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88809fee2d80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88809fee2e00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

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