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

Status: fixed on 2018/11/12 21:25
Subsystems: bpf net
[Documentation on labels]
Fix commit: 5032d079909d bpf: skmsg, fix psock create on existing kcm/tls port
First crash: 2048d, last: 2047d

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
BUG: KASAN: slab-out-of-bounds in refcount_inc_not_zero_checked+0x97/0x2f0 lib/refcount.c:120
Read of size 4 at addr ffff880197edde58 by task syz-executor1/12843

CPU: 1 PID: 12843 Comm: syz-executor1 Not tainted 4.19.0-rc7+ #265
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+0x1c4/0x2b4 lib/dump_stack.c:113
 print_address_description.cold.8+0x9/0x1ff mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.9+0x242/0x309 mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 kasan_check_read+0x11/0x20 mm/kasan/kasan.c:272
 atomic_read include/asm-generic/atomic-instrumented.h:21 [inline]
 refcount_inc_not_zero_checked+0x97/0x2f0 lib/refcount.c:120
 sk_psock_get include/linux/skmsg.h:379 [inline]
 sock_map_link.isra.6+0x41f/0xe30 net/core/sock_map.c:178
 sock_hash_update_common+0x19b/0x11e0 net/core/sock_map.c:669
 sock_hash_update_elem+0x306/0x470 net/core/sock_map.c:738
 map_update_elem+0x819/0xdf0 kernel/bpf/syscall.c:818
 __do_sys_bpf kernel/bpf/syscall.c:2400 [inline]
 __se_sys_bpf kernel/bpf/syscall.c:2371 [inline]
 __x64_sys_bpf+0x32d/0x510 kernel/bpf/syscall.c:2371
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457569
Code: fd b3 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 b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007fefc863fc78 EFLAGS: 00000246 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000457569
RDX: 0000000000000020 RSI: 0000000020000280 RDI: 0000000000000002
RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fefc86406d4
R13: 00000000004bd926 R14: 00000000004cc2b0 R15: 00000000ffffffff

Allocated by task 12843:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554
 kmem_cache_zalloc include/linux/slab.h:697 [inline]
 kcm_attach net/kcm/kcmsock.c:1405 [inline]
 kcm_attach_ioctl net/kcm/kcmsock.c:1490 [inline]
 kcm_ioctl+0xca7/0x18c0 net/kcm/kcmsock.c:1696
 sock_do_ioctl+0xeb/0x420 net/socket.c:950
 sock_ioctl+0x313/0x690 net/socket.c:1074
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:501 [inline]
 do_vfs_ioctl+0x1de/0x1720 fs/ioctl.c:685
 ksys_ioctl+0xa9/0xd0 fs/ioctl.c:702
 __do_sys_ioctl fs/ioctl.c:709 [inline]
 __se_sys_ioctl fs/ioctl.c:707 [inline]
 __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:707
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 0:
(stack is not available)

The buggy address belongs to the object at ffff880197eddc00
 which belongs to the cache kcm_psock_cache of size 544
The buggy address is located 56 bytes to the right of
 544-byte region [ffff880197eddc00, ffff880197edde20)
The buggy address belongs to the page:
page:ffffea00065fb700 count:1 mapcount:0 mapping:ffff8801cb995800 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801cb553148 ffff8801cb553148 ffff8801cb995800
raw: 0000000000000000 ffff880197edc080 000000010000000b 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880197eddd00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff880197eddd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff880197edde00: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
                                                    ^
 ffff880197edde80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff880197eddf00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/10/18 05:30 net-next-old 53e50a6ec24d b2695b95 .config console log report ci-upstream-net-kasan-gce
2018/10/17 11:46 net-next-old aadd4355918f 1ba7fd7e .config console log report ci-upstream-net-kasan-gce
* Struck through repros no longer work on HEAD.