syzbot


KASAN: stack-out-of-bounds Read in tlb_flush_mmu_free

Status: fixed on 2018/08/07 13:43
Subsystems: mm
[Documentation on labels]
Reported-by: syzbot+97e27b3573081d2b07bf@syzkaller.appspotmail.com
Fix commit: 99ba2b5aba24 bpf: sockhash, disallow bpf_tcp_close and update in parallel
First crash: 2140d, last: 2137d

Sample crash report:
==================================================================
BUG: KASAN: stack-out-of-bounds in tlb_flush_mmu_free+0x13f/0x160 mm/memory.c:258
Read of size 4 at addr ffff880195a4d008 by task syz-executor1/8636

CPU: 1 PID: 8636 Comm: syz-executor1 Not tainted 4.18.0-rc3+ #50
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+0x1c9/0x2b4 lib/dump_stack.c:113
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
 __asan_report_load4_noabort+0x14/0x20 mm/kasan/report.c:432
 tlb_flush_mmu_free+0x13f/0x160 mm/memory.c:258
 zap_pte_range mm/memory.c:1400 [inline]
 zap_pmd_range mm/memory.c:1437 [inline]
 zap_pud_range mm/memory.c:1466 [inline]
 zap_p4d_range mm/memory.c:1487 [inline]
 unmap_page_range+0x1a45/0x2220 mm/memory.c:1508
 unmap_single_vma+0x1a0/0x310 mm/memory.c:1553
 unmap_vmas+0x120/0x1f0 mm/memory.c:1583
 exit_mmap+0x2c2/0x5b0 mm/mmap.c:3105
 __mmput kernel/fork.c:970 [inline]
 mmput+0x265/0x620 kernel/fork.c:991
 exit_mm kernel/exit.c:544 [inline]
 do_exit+0xea9/0x2750 kernel/exit.c:852
 do_group_exit+0x177/0x440 kernel/exit.c:968
 get_signal+0x88e/0x1970 kernel/signal.c:2468
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e0/0x370 arch/x86/entry/common.c:162
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x455a79
Code: 1d ba 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 eb b9 fb ff c3 66 2e 0f 1f 84 00 00 00 00 
RSP: 002b:00007fa605d95ce8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 000000000072bf68 RCX: 0000000000455a79
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000072bf68
RBP: 000000000072bf68 R08: 0000000000000000 R09: 000000000072bf48
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffe5708f09f R14: 00007fa605d969c0 R15: 0000000000000001

The buggy address belongs to the page:
page:ffffea0006569340 count:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0x2fffc0000000000()
raw: 02fffc0000000000 dead000000000100 dead000000000200 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff880195a4cf00: 00 f1 f1 f1 f1 00 f2 f2 f2 f2 f2 f2 f2 00 f2 f2
 ffff880195a4cf80: f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2 f2 f2 f8 f2 f2
>ffff880195a4d000: f2 f2 f2 f2 f2 00 f2 f2 f2 00 00 00 00 00 00 00
                      ^
 ffff880195a4d080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1
 ffff880195a4d100: f1 f1 00 f2 f2 f2 f2 f2 f2 f2 00 f2 f2 f2 f2 f2
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2018/07/12 15:12 bpf-next 671dffa7de7b 06c33b3a .config console log report ci-upstream-bpf-next-kasan-gce
2018/07/09 20:35 bpf-next d90c936fb318 f25e5770 .config console log report ci-upstream-bpf-next-kasan-gce
* Struck through repros no longer work on HEAD.