syzbot


KASAN: use-after-free Read in sctp_auth_free
Status: fixed on 2020/11/16 12:12
Reported-by: syzbot+@syzkaller.appspotmail.com
Fix commit: d42ee76ecb6c net-backports: sctp: fix sctp_auth_init_hmacs() error path
First crash: 594d, last: 593d

Cause bisection: introduced by (bisect log) :
commit 56dd525abd56f7acd7b44a52935726e3ada4916c
Author: Xin Long <lucien.xin@gmail.com>
Date: Mon Aug 19 14:02:49 2019 +0000

  sctp: add SCTP_AUTH_SUPPORTED sockopt

Crash: KASAN: use-after-free Read in sctp_auth_destroy_hmacs (log)
Repro: C syz .config

Sample crash report:
RBP: 00000000006cb018 R08: 0000000000000008 R09: 00000000004002c8
R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000401e20
R13: 0000000000401eb0 R14: 0000000000000000 R15: 0000000000000000
==================================================================
BUG: KASAN: use-after-free in sctp_auth_destroy_hmacs net/sctp/auth.c:509 [inline]
BUG: KASAN: use-after-free in sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline]
BUG: KASAN: use-after-free in sctp_auth_free+0x17e/0x1d0 net/sctp/auth.c:1070
Read of size 8 at addr ffff8880a8ff52c0 by task syz-executor941/6874

CPU: 0 PID: 6874 Comm: syz-executor941 Not tainted 5.9.0-rc8-syzkaller #0
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+0x198/0x1fd lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x497 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 sctp_auth_destroy_hmacs net/sctp/auth.c:509 [inline]
 sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline]
 sctp_auth_free+0x17e/0x1d0 net/sctp/auth.c:1070
 sctp_endpoint_destroy+0x95/0x240 net/sctp/endpointola.c:203
 sctp_endpoint_put net/sctp/endpointola.c:236 [inline]
 sctp_endpoint_free+0xd6/0x110 net/sctp/endpointola.c:183
 sctp_destroy_sock+0x9c/0x3c0 net/sctp/socket.c:4981
 sctp_v6_destroy_sock+0x11/0x20 net/sctp/socket.c:9415
 sk_common_release+0x64/0x390 net/core/sock.c:3254
 sctp_close+0x4ce/0x8b0 net/sctp/socket.c:1533
 inet_release+0x12e/0x280 net/ipv4/af_inet.c:431
 inet6_release+0x4c/0x70 net/ipv6/af_inet6.c:475
 __sock_release+0xcd/0x280 net/socket.c:596
 sock_close+0x18/0x20 net/socket.c:1277
 __fput+0x285/0x920 fs/file_table.c:281
 task_work_run+0xdd/0x190 kernel/task_work.c:141
 exit_task_work include/linux/task_work.h:25 [inline]
 do_exit+0xb7d/0x29f0 kernel/exit.c:806
 do_group_exit+0x125/0x310 kernel/exit.c:903
 __do_sys_exit_group kernel/exit.c:914 [inline]
 __se_sys_exit_group kernel/exit.c:912 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:912
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x43f278
Code: Bad RIP value.
RSP: 002b:00007fffe0995c38 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043f278
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf068 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 0000000020000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d1180 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 6874:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xbf/0xd0 mm/kasan/common.c:461
 kmem_cache_alloc_trace+0x174/0x300 mm/slab.c:3554
 kmalloc include/linux/slab.h:554 [inline]
 kmalloc_array include/linux/slab.h:593 [inline]
 kcalloc include/linux/slab.h:605 [inline]
 sctp_auth_init_hmacs+0xdb/0x3b0 net/sctp/auth.c:464
 sctp_auth_init+0x8a/0x4a0 net/sctp/auth.c:1049
 sctp_setsockopt_auth_supported net/sctp/socket.c:4354 [inline]
 sctp_setsockopt+0x477e/0x97f0 net/sctp/socket.c:4631
 __sys_setsockopt+0x2db/0x610 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2143 [inline]
 __se_sys_setsockopt net/socket.c:2140 [inline]
 __x64_sys_setsockopt+0xba/0x150 net/socket.c:2140
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Freed by task 6874:
 kasan_save_stack+0x1b/0x40 mm/kasan/common.c:48
 kasan_set_track+0x1c/0x30 mm/kasan/common.c:56
 kasan_set_free_info+0x1b/0x30 mm/kasan/generic.c:355
 __kasan_slab_free+0xd8/0x120 mm/kasan/common.c:422
 __cache_free mm/slab.c:3422 [inline]
 kfree+0x10e/0x2b0 mm/slab.c:3760
 sctp_auth_destroy_hmacs net/sctp/auth.c:511 [inline]
 sctp_auth_destroy_hmacs net/sctp/auth.c:501 [inline]
 sctp_auth_init_hmacs net/sctp/auth.c:496 [inline]
 sctp_auth_init_hmacs+0x2b7/0x3b0 net/sctp/auth.c:454
 sctp_auth_init+0x8a/0x4a0 net/sctp/auth.c:1049
 sctp_setsockopt_auth_supported net/sctp/socket.c:4354 [inline]
 sctp_setsockopt+0x477e/0x97f0 net/sctp/socket.c:4631
 __sys_setsockopt+0x2db/0x610 net/socket.c:2132
 __do_sys_setsockopt net/socket.c:2143 [inline]
 __se_sys_setsockopt net/socket.c:2140 [inline]
 __x64_sys_setsockopt+0xba/0x150 net/socket.c:2140
 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

The buggy address belongs to the object at ffff8880a8ff52c0
 which belongs to the cache kmalloc-32 of size 32
The buggy address is located 0 bytes inside of
 32-byte region [ffff8880a8ff52c0, ffff8880a8ff52e0)
The buggy address belongs to the page:
page:00000000f7133596 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff8880a8ff5fc1 pfn:0xa8ff5
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002861548 ffffea0002872f08 ffff8880aa040100
raw: ffff8880a8ff5fc1 ffff8880a8ff5000 000000010000003f 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880a8ff5180: 06 fc fc fc fc fc fc fc fa fb fb fb fc fc fc fc
 ffff8880a8ff5200: 00 06 fc fc fc fc fc fc fb fb fb fb fc fc fc fc
>ffff8880a8ff5280: 00 05 fc fc fc fc fc fc fa fb fb fb fc fc fc fc
                                           ^
 ffff8880a8ff5300: 00 00 00 06 fc fc fc fc fb fb fb fb fc fc fc fc
 ffff8880a8ff5380: 00 00 06 fc fc fc fc fc fb fb fb fb fc fc fc fc
==================================================================

Crashes (4):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce 2020/10/07 18:40 upstream c85fb28b6f99 1880b4a9 .config log report syz C
ci-upstream-kasan-gce 2020/10/09 04:31 upstream 3d006ee42dde 92390980 .config log report info
ci-upstream-kasan-gce 2020/10/07 18:28 upstream c85fb28b6f99 1880b4a9 .config log report info
ci-upstream-net-this-kasan-gce 2020/10/08 02:03 net d91dc434f2ba 1880b4a9 .config log report info