KASAN: slab-out-of-bounds Read in do_jit

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 89099d85 Merge branch 'flow_offload-fixes'
git tree: net
console output: https://syzkaller.appspot.com/x/log.txt?x=17169bb7a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=4dba67bf8b8c9ad7
dashboard link: https://syzkaller.appspot.com/bug?extid=6b40f58c6d280fa23b40
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=117364f0600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=11fcbaafa00000

The bug was bisected to:

commit 2589726d12a1b12eaaa93c7f1ea64287e383c7a5
Author: Alexei Starovoitov <a...@kernel.org>
Date: Sat Jun 15 19:12:20 2019 +0000

bpf: introduce bounded loops

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15d38fa4600000
final crash: https://syzkaller.appspot.com/x/report.txt?x=17d38fa4600000
console output: https://syzkaller.appspot.com/x/log.txt?x=13d38fa4600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6b40f5...@syzkaller.appspotmail.com
Fixes: 2589726d12a1 ("bpf: introduce bounded loops")

==================================================================
BUG: KASAN: slab-out-of-bounds in do_jit.isra.0+0x4c35/0x5630
/arch/x86/net/bpf_jit_comp.c:966
Read of size 4 at addr ffff8880a654ec3c by task syz-executor906/8876

CPU: 0 PID: 8876 Comm: syz-executor906 Not tainted 5.2.0+ #95
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+0x12/0x17 /mm/kasan/common.c:612
__asan_report_load4_noabort+0x14/0x20 /mm/kasan/generic_report.c:131
do_jit.isra.0+0x4c35/0x5630 /arch/x86/net/bpf_jit_comp.c:966
bpf_int_jit_compile+0x374/0xda0 /arch/x86/net/bpf_jit_comp.c:1132
bpf_prog_select_runtime+0x4cd/0x7d0 /kernel/bpf/core.c:1726
bpf_prog_load+0xe9b/0x1670 /kernel/bpf/syscall.c:1702
__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: 0033:0x4402c9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffc7d7bb638 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004402c9
RDX: 0000000000000046 RSI: 0000000020000180 RDI: 0000000000000005
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 00000000ffffffff R11: 0000000000000246 R12: 0000000000401b50
R13: 0000000000401be0 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 8388:
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
__do_kmalloc /mm/slab.c:3655 [inline]
__kmalloc+0x163/0x770 /mm/slab.c:3664
kmalloc /./include/linux/slab.h:557 [inline]
kzalloc /./include/linux/slab.h:748 [inline]
lsm_cred_alloc /security/security.c:466 [inline]
security_prepare_creds+0x11d/0x190 /security/security.c:1514
prepare_creds+0x2f5/0x3f0 /kernel/cred.c:281
do_faccessat+0xa2/0x7f0 /fs/open.c:360
__do_sys_access /fs/open.c:431 [inline]
__se_sys_access /fs/open.c:429 [inline]
__x64_sys_access+0x59/0x80 /fs/open.c:429
do_syscall_64+0xfd/0x6a0 /arch/x86/entry/common.c:296
entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 8372:
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
security_cred_free+0xa9/0x110 /security/security.c:1508
put_cred_rcu+0x129/0x4b0 /kernel/cred.c:114
__rcu_reclaim /kernel/rcu/rcu.h:222 [inline]
rcu_do_batch /kernel/rcu/tree.c:2114 [inline]
rcu_core+0x67f/0x1580 /kernel/rcu/tree.c:2314
rcu_core_si+0x9/0x10 /kernel/rcu/tree.c:2323
__do_softirq+0x262/0x98c /kernel/softirq.c:292

The buggy address belongs to the object at ffff8880a654ec00
which belongs to the cache kmalloc-32 of size 32
The buggy address is located 28 bytes to the right of
32-byte region [ffff8880a654ec00, ffff8880a654ec20)
The buggy address belongs to the page:
page:ffffea0002995380 refcount:1 mapcount:0 mapping:ffff8880aa4001c0
index:0xffff8880a654efc1
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea000290f1c8 ffffea0002a154c8 ffff8880aa4001c0
raw: ffff8880a654efc1 ffff8880a654e000 0000000100000027 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
ffff8880a654eb00: fb fb fb fb fc fc fc fc 00 04 fc fc fc fc fc fc
ffff8880a654eb80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
> ffff8880a654ec00: fb fb fb fb fc fc fc fc 00 00 fc fc fc fc fc fc
^
ffff8880a654ec80: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
ffff8880a654ed00: fb fb fb fb fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================


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