KASAN: use-after-free Read in io_uring_setup

From: syzbot
Date: Mon Oct 28 2019 - 03:22:11 EST


syzbot found the following crash on:

HEAD commit: 5a1e843c Merge tag 'mips_fixes_5.4_3' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10e2001f600000
kernel config: https://syzkaller.appspot.com/x/.config?x=420126a10fdda0f1
dashboard link: https://syzkaller.appspot.com/bug?extid=6f03d895a6cd0d06187f
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=11d4fa97600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+6f03d895a6cd0d06187f@xxxxxxxxxxxxxxxxxxxxxxxxx

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
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

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

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

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