syzbot


KASAN: slab-out-of-bounds Write in array_map_update_elem

Status: fixed on 2018/01/22 13:19
Subsystems: bpf
[Documentation on labels]
Reported-by: syzbot+23dc48712d6941968d1f@syzkaller.appspotmail.com
Fix commit: bbeb6e4323da bpf, array: fix overflow in max_entries and undefined behavior in index_mask
First crash: 2321d, last: 2318d
Discussions (1)
Title Replies (including bot) Last reply
KASAN: slab-out-of-bounds Write in array_map_update_elem 2 (3) 2018/01/15 23:00

Sample crash report:
audit: type=1400 audit(1515679662.716:8): avc:  denied  { sys_admin } for  pid=3485 comm="syzkaller377846" capability=21  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
audit: type=1400 audit(1515679662.770:9): avc:  denied  { sys_chroot } for  pid=3486 comm="syzkaller377846" capability=18  scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=cap_userns permissive=1
==================================================================
BUG: KASAN: slab-out-of-bounds in memcpy include/linux/string.h:344 [inline]
BUG: KASAN: slab-out-of-bounds in array_map_update_elem+0x197/0x240 kernel/bpf/arraymap.c:249
Write of size 1 at addr ffff8801cb0a3900 by task syzkaller377846/3486

CPU: 1 PID: 3486 Comm: syzkaller377846 Not tainted 4.15.0-rc7-mm1+ #53
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:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report+0x23b/0x360 mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x137/0x190 mm/kasan/kasan.c:267
 memcpy+0x37/0x50 mm/kasan/kasan.c:303
 memcpy include/linux/string.h:344 [inline]
 array_map_update_elem+0x197/0x240 kernel/bpf/arraymap.c:249
 map_update_elem kernel/bpf/syscall.c:687 [inline]
 SYSC_bpf kernel/bpf/syscall.c:1811 [inline]
 SyS_bpf+0x32df/0x4400 kernel/bpf/syscall.c:1782
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x440ac9
RSP: 002b:00000000007dff68 EFLAGS: 00000203 ORIG_RAX: 0000000000000141
RAX: ffffffffffffffda RBX: 00007ffc88b23300 RCX: 0000000000440ac9
RDX: 0000000000000020 RSI: 0000000020eaf000 RDI: 0000000000000002
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000203 R12: 00000000004022a0
R13: 0000000000402330 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 3072:
 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:552
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:489
 kmem_cache_alloc+0x12e/0x760 mm/slab.c:3541
 getname_kernel+0x54/0x340 fs/namei.c:218
 open_exec+0x17/0x60 fs/exec.c:877
 load_elf_binary+0x1348/0x4c10 fs/binfmt_elf.c:780
 search_binary_handler+0x142/0x6b0 fs/exec.c:1639
 exec_binprm fs/exec.c:1681 [inline]
 do_execveat_common.isra.30+0x1711/0x22a0 fs/exec.c:1803
 do_execve fs/exec.c:1848 [inline]
 SYSC_execve fs/exec.c:1929 [inline]
 SyS_execve+0x39/0x50 fs/exec.c:1924
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

Freed by task 3072:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:447
 set_track mm/kasan/kasan.c:459 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:520
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:527
 __cache_free mm/slab.c:3485 [inline]
 kmem_cache_free+0x86/0x2b0 mm/slab.c:3743
 putname+0xee/0x130 fs/namei.c:258
 open_exec+0x41/0x60 fs/exec.c:882
 load_elf_binary+0x1348/0x4c10 fs/binfmt_elf.c:780
 search_binary_handler+0x142/0x6b0 fs/exec.c:1639
 exec_binprm fs/exec.c:1681 [inline]
 do_execveat_common.isra.30+0x1711/0x22a0 fs/exec.c:1803
 do_execve fs/exec.c:1848 [inline]
 SYSC_execve fs/exec.c:1929 [inline]
 SyS_execve+0x39/0x50 fs/exec.c:1924
 do_syscall_64+0x273/0x920 arch/x86/entry/common.c:285
 return_from_SYSCALL_64+0x0/0x75

The buggy address belongs to the object at ffff8801cb0a2380
 which belongs to the cache names_cache of size 4096
The buggy address is located 1408 bytes to the right of
 4096-byte region [ffff8801cb0a2380, ffff8801cb0a3380)
The buggy address belongs to the page:
page:ffffea00072c2880 count:1 mapcount:0 mapping:ffff8801cb0a2380 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffff8801cb0a2380 0000000000000000 0000000100000001
raw: ffffea00072c2920 ffffea00072b95a0 ffff8801dae30600 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801cb0a3800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cb0a3880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801cb0a3900: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
                   ^
 ffff8801cb0a3980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801cb0a3a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (6):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/01/11 14:10 mmots 4147d50978df 9dc808a6 .config console log report syz C ci-upstream-mmots-kasan-gce
2018/01/15 01:21 net-next-old 1988c7957881 66d492a6 .config console log report ci-upstream-net-kasan-gce
2018/01/14 18:49 net-next-old 1988c7957881 66d492a6 .config console log report ci-upstream-net-kasan-gce
2018/01/13 07:17 net-next-old 6bd39bc3da0f 9dc808a6 .config console log report ci-upstream-net-kasan-gce
2018/01/12 16:03 net-next-old 19d28fbd306e 9dc808a6 .config console log report ci-upstream-net-kasan-gce
2018/01/13 01:29 mmots 2c405fa05106 9dc808a6 .config console log report ci-upstream-mmots-kasan-gce
* Struck through repros no longer work on HEAD.