syzbot


KASAN: use-after-free Read in io_uring_setup

Status: fixed on 2019/11/23 02:56
Subsystems: fs
[Documentation on labels]
Reported-by: syzbot+6f03d895a6cd0d06187f@syzkaller.appspotmail.com
Fix commit: 044c1ab399af io_uring: don't touch ctx in setup after ring fd install
First crash: 1694d, last: 1694d
Cause bisection: failed (error log, bisect log)
  
Discussions (1)
Title Replies (including bot) Last reply
KASAN: use-after-free Read in io_uring_setup 2 (3) 2019/10/28 15:15
Similar bugs (1)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in io_uring_setup (2) fs 1 1417d 1417d 15/27 fixed on 2020/09/16 22:51

Sample crash report:
==================================================================
BUG: KASAN: use-after-free in io_uring_create fs/io_uring.c:3842 [inline]
BUG: KASAN: use-after-free in io_uring_setup+0x1877/0x18c0 fs/io_uring.c:3881
Read of size 8 at addr ffff888082284048 by task syz-executor.5/11342

CPU: 1 PID: 11342 Comm: syz-executor.5 Not tainted 5.4.0-rc4+ #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+0x172/0x1f0 lib/dump_stack.c:113
 print_address_description.constprop.0.cold+0xd4/0x30b mm/kasan/report.c:374
 __kasan_report.cold+0x1b/0x41 mm/kasan/report.c:506
 kasan_report+0x12/0x20 mm/kasan/common.c:634
 __asan_report_load8_noabort+0x14/0x20 mm/kasan/generic_report.c:132
 io_uring_create fs/io_uring.c:3842 [inline]
 io_uring_setup+0x1877/0x18c0 fs/io_uring.c:3881
 __do_sys_io_uring_setup fs/io_uring.c:3894 [inline]
 __se_sys_io_uring_setup fs/io_uring.c:3891 [inline]
 __x64_sys_io_uring_setup+0x54/0x80 fs/io_uring.c:3891
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459f39
Code: ad b6 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 7b b6 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f313e126c78 EFLAGS: 00000246 ORIG_RAX: 00000000000001a9
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459f39
RDX: 0000000000000000 RSI: 00000000200005c0 RDI: 000000040000000e
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f313e1276d4
R13: 00000000004c1512 R14: 00000000004d4da8 R15: 00000000ffffffff

Allocated by task 11342:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 __kasan_kmalloc mm/kasan/common.c:510 [inline]
 __kasan_kmalloc.constprop.0+0xcf/0xe0 mm/kasan/common.c:483
 kasan_kmalloc+0x9/0x10 mm/kasan/common.c:524
 kmem_cache_alloc_trace+0x158/0x790 mm/slab.c:3550
 kmalloc include/linux/slab.h:556 [inline]
 kzalloc include/linux/slab.h:690 [inline]
 io_ring_ctx_alloc fs/io_uring.c:393 [inline]
 io_uring_create fs/io_uring.c:3811 [inline]
 io_uring_setup+0xec6/0x18c0 fs/io_uring.c:3881
 __do_sys_io_uring_setup fs/io_uring.c:3894 [inline]
 __se_sys_io_uring_setup fs/io_uring.c:3891 [inline]
 __x64_sys_io_uring_setup+0x54/0x80 fs/io_uring.c:3891
 do_syscall_64+0xfa/0x760 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 11335:
 save_stack+0x23/0x90 mm/kasan/common.c:69
 set_track mm/kasan/common.c:77 [inline]
 kasan_set_free_info mm/kasan/common.c:332 [inline]
 __kasan_slab_free+0x102/0x150 mm/kasan/common.c:471
 kasan_slab_free+0xe/0x10 mm/kasan/common.c:480
 __cache_free mm/slab.c:3425 [inline]
 kfree+0x10a/0x2c0 mm/slab.c:3756
 io_ring_ctx_free fs/io_uring.c:3552 [inline]
 io_ring_ctx_wait_and_kill+0x4d7/0x6c0 fs/io_uring.c:3592
 io_uring_release+0x42/0x50 fs/io_uring.c:3600
 __fput+0x2ff/0x890 fs/file_table.c:280
 ____fput+0x16/0x20 fs/file_table.c:313
 task_work_run+0x145/0x1c0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
 prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
 do_syscall_64+0x65f/0x760 arch/x86/entry/common.c:300
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff888082284000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 72 bytes inside of
 2048-byte region [ffff888082284000, ffff888082284800)
The buggy address belongs to the page:
page:ffffea000208a100 refcount:1 mapcount:0 mapping:ffff8880aa400e00 index:0x0
flags: 0x1fffc0000000200(slab)
raw: 01fffc0000000200 ffffea0002a1bc88 ffffea00023fa248 ffff8880aa400e00
raw: 0000000000000000 ffff888082284000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888082283f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888082283f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888082284000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                              ^
 ffff888082284080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888082284100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2019/10/27 17:17 upstream 5a1e843c66fa 25bb509e .config console log report syz ci-upstream-kasan-gce
* Struck through repros no longer work on HEAD.