| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <883b3cf9-1d92-a22f-e946-0936d09d36c0@kernel.dk>
Date: Mon, 28 Oct 2019 08:09:57 -0600
From: Jens Axboe <axboe@...nel.dk>
To: syzbot <syzbot+6f03d895a6cd0d06187f@...kaller.appspotmail.com>,
linux-block@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
viro@...iv.linux.org.uk
Subject: Re: KASAN: use-after-free Read in io_uring_setup
On 10/28/19 1:22 AM, syzbot wrote:
> Hello,
>
> 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@...kaller.appspotmail.com
>
> ==================================================================
> 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
> ==================================================================
Interesting, looks like a malicious case that attempts to close the
fd as soon as it's installed. As a result of that, the rest of the
setup will be done on a ring that's already torn down. The below should
fix that.
Totally untested, haven't tried the reproducer yet.
diff --git a/fs/io_uring.c b/fs/io_uring.c
index ba1431046c98..749637ca9cf7 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -3821,6 +3821,12 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
ctx->account_mem = account_mem;
ctx->user = user;
+ /*
+ * Grab an initial reference to the ctx, so we ensure we have one
+ * by the time the fd is installed.
+ */
+ percpu_ref_get(&ctx->refs);
+
ret = io_allocate_scq_urings(ctx, p);
if (ret)
goto err;
@@ -3851,8 +3857,10 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
p->cq_off.cqes = offsetof(struct io_rings, cqes);
p->features = IORING_FEAT_SINGLE_MMAP;
+ percpu_ref_put(&ctx->refs);
return ret;
err:
+ percpu_ref_put(&ctx->refs);
io_ring_ctx_wait_and_kill(ctx);
return ret;
}
--
Jens Axboe
Powered by blists - more mailing lists