Re: linux-next: BUG: KASAN: use-after-free in tun_chr_close
On 2018年05月16日 15:40, Andrei Vagin wrote: On Wed, May 16, 2018 at 03:32:59PM +0800, Jason Wang wrote: On 2018年05月16日 15:12, Andrei Vagin wrote: Hi Jason, I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup". Pls take a look at the attached patch. Yes. It looks to me it's not necessary to take extra refcnt during release, we can just do the cleanup at __tun_detach(). Could you help to test the attached patch? I've run my test on the kernel with this patch. It fixes the problem. The patch looks correct for me. Acked-by: Andrei Vagin Cool, thanks a lot! Let me post a formal patch.
Re: linux-next: BUG: KASAN: use-after-free in tun_chr_close
On Wed, May 16, 2018 at 03:32:59PM +0800, Jason Wang wrote:
>
>
> On 2018年05月16日 15:12, Andrei Vagin wrote:
> > Hi Jason,
> >
> > I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup".
> >
> > Pls take a look at the attached patch.
>
> Yes.
>
> It looks to me it's not necessary to take extra refcnt during release, we
> can just do the cleanup at __tun_detach().
>
> Could you help to test the attached patch?
I've run my test on the kernel with this patch. It fixes the problem.
The patch looks correct for me.
Acked-by: Andrei Vagin
>
> Thanks
>
> From 4b5ad75208e379dcb32abb9ac4790a0446f8558b Mon Sep 17 00:00:00 2001
> From: Jason Wang
> Date: Wed, 16 May 2018 15:26:52 +0800
> Subject: [PATCH] tuntap: fix use after free during release
>
> After commit b196d88aba8a ("tun: fix use after free for ptr_ring") we
> need clean up tx ring during release(). But unfortunately, it tries to
> do the cleanup after socket were destroyed which will lead another
> use-after-free. Fix this by doing the cleanup before dropping the last
> reference of the socket in __tun_detach().
>
> Reported-by: Andrei Vagin
> Fixes: b196d88aba8a ("tun: fix use after free for ptr_ring")
> Signed-off-by: Jason Wang
> ---
> drivers/net/tun.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 9fbbb32..d45ac37 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -729,6 +729,7 @@ static void __tun_detach(struct tun_file *tfile, bool
> clean)
> }
> if (tun)
> xdp_rxq_info_unreg(&tfile->xdp_rxq);
> + ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
> sock_put(&tfile->sk);
> }
> }
> @@ -3245,7 +3246,6 @@ static int tun_chr_close(struct inode *inode, struct
> file *file)
> struct tun_file *tfile = file->private_data;
>
> tun_detach(tfile, true);
> - ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
>
> return 0;
> }
> --
> 2.7.4
>
Re: linux-next: BUG: KASAN: use-after-free in tun_chr_close
On 2018年05月16日 15:12, Andrei Vagin wrote:
Hi Jason,
I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup".
Pls take a look at the attached patch.
Yes.
It looks to me it's not necessary to take extra refcnt during release,
we can just do the cleanup at __tun_detach().
Could you help to test the attached patch?
Thanks
>From 4b5ad75208e379dcb32abb9ac4790a0446f8558b Mon Sep 17 00:00:00 2001
From: Jason Wang
Date: Wed, 16 May 2018 15:26:52 +0800
Subject: [PATCH] tuntap: fix use after free during release
After commit b196d88aba8a ("tun: fix use after free for ptr_ring") we
need clean up tx ring during release(). But unfortunately, it tries to
do the cleanup after socket were destroyed which will lead another
use-after-free. Fix this by doing the cleanup before dropping the last
reference of the socket in __tun_detach().
Reported-by: Andrei Vagin
Fixes: b196d88aba8a ("tun: fix use after free for ptr_ring")
Signed-off-by: Jason Wang
---
drivers/net/tun.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9fbbb32..d45ac37 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -729,6 +729,7 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
}
if (tun)
xdp_rxq_info_unreg(&tfile->xdp_rxq);
+ ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
sock_put(&tfile->sk);
}
}
@@ -3245,7 +3246,6 @@ static int tun_chr_close(struct inode *inode, struct file *file)
struct tun_file *tfile = file->private_data;
tun_detach(tfile, true);
- ptr_ring_cleanup(&tfile->tx_ring, tun_ptr_free);
return 0;
}
--
2.7.4
Re: linux-next: BUG: KASAN: use-after-free in tun_chr_close
Hi Jason, I think the problem is in "tun: hold a tun socket during ptr_ring_cleanup". Pls take a look at the attached patch. On Tue, May 15, 2018 at 11:28:25PM -0700, Andrei Vagin wrote: > We run CRIU tests on linux-next regularly and today we caught this bug: > > https://travis-ci.org/avagin/linux/jobs/379450631 > > [ 50.264837] > == > [ 50.264986] BUG: KASAN: use-after-free in > __lock_acquire.isra.30+0x1ad4/0x1bb0 > [ 50.265088] Read of size 8 at addr 88018e1728f8 by task criu/1819 > [ 50.265167] > [ 50.265249] CPU: 0 PID: 1819 Comm: criu Not tainted > 4.17.0-rc5-next-20180515+ #1 > [ 50.265251] Hardware name: Google Google Compute Engine/Google Compute > Engine, BIOS Google 01/01/2011 > [ 50.265252] Call Trace: > [ 50.265262] dump_stack+0x71/0xab > [ 50.265265] ? __lock_acquire.isra.30+0x1ad4/0x1bb0 > [ 50.265271] print_address_description+0x6a/0x270 > [ 50.265273] ? __lock_acquire.isra.30+0x1ad4/0x1bb0 > [ 50.265275] kasan_report+0x237/0x360 > [ 50.265278] __lock_acquire.isra.30+0x1ad4/0x1bb0 > [ 50.265285] ? register_netdev+0x30/0x30 > [ 50.265288] lock_acquire+0x10b/0x2a0 > [ 50.265294] ? tun_chr_close+0x1d7/0x4c0 > [ 50.265298] ? kfree+0xd6/0x1f0 > [ 50.265303] _raw_spin_lock+0x25/0x30 > [ 50.265306] ? tun_chr_close+0x1d7/0x4c0 > [ 50.265308] tun_chr_close+0x1d7/0x4c0 > [ 50.265313] ? fcntl_setlk+0xaf0/0xaf0 > [ 50.265320] __fput+0x251/0x770 > [ 50.265324] task_work_run+0x10e/0x180 > [ 50.265330] exit_to_usermode_loop+0xcb/0xf0 > [ 50.265332] do_syscall_64+0x21d/0x280 > [ 50.265335] ? prepare_exit_to_usermode+0x88/0x130 > [ 50.265338] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 50.265342] RIP: 0033:0x1494fa6f93f0 > [ 50.265342] Code: 73 01 c3 48 8b 0d b8 9b 20 00 f7 d8 64 89 01 48 83 c8 ff > c3 66 0f 1f 44 00 00 83 3d 59 e0 20 00 00 75 10 b8 03 00 00 00 0f 05 <48> 3d > 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 0e fa ff ff 48 89 04 24 > [ 50.265388] RSP: 002b:7ffd229fe7f8 EFLAGS: 0246 ORIG_RAX: > 0003 > [ 50.265391] RAX: RBX: 0004 RCX: > 1494fa6f93f0 > [ 50.265393] RDX: 7ffd229fe80c RSI: 400454da RDI: > 0004 > [ 50.265395] RBP: R08: 420b R09: > > [ 50.265396] R10: R11: 0246 R12: > 1494fab116a0 > [ 50.265398] R13: 0d06 R14: R15: > > [ 50.265400] > [ 50.265476] Allocated by task 1819: > [ 50.265554] kasan_kmalloc+0xa0/0xd0 > [ 50.265556] __kmalloc+0x13a/0x250 > [ 50.265561] sk_prot_alloc+0xd3/0x250 > [ 50.265564] sk_alloc+0x35/0x9d0 > [ 50.265566] tun_chr_open+0x7b/0x5a0 > [ 50.265570] misc_open+0x313/0x480 > [ 50.265573] chrdev_open+0x1d6/0x4b0 > [ 50.265575] do_dentry_open+0x6ae/0xee0 > [ 50.265578] path_openat+0xce6/0x2890 > [ 50.265580] do_filp_open+0x17a/0x270 > [ 50.265582] do_sys_open+0x203/0x340 > [ 50.265584] do_syscall_64+0xa0/0x280 > [ 50.265586] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 50.265587] > [ 50.265667] Freed by task 1819: > [ 50.265745] __kasan_slab_free+0x130/0x180 > [ 50.265747] kfree+0xd6/0x1f0 > [ 50.265750] __sk_destruct+0x46f/0x580 > [ 50.265752] tun_chr_close+0x330/0x4c0 > [ 50.265754] __fput+0x251/0x770 > [ 50.265756] task_work_run+0x10e/0x180 > [ 50.265758] exit_to_usermode_loop+0xcb/0xf0 > [ 50.265760] do_syscall_64+0x21d/0x280 > [ 50.265762] entry_SYSCALL_64_after_hwframe+0x44/0xa9 > [ 50.265762] > [ 50.265840] The buggy address belongs to the object at 88018e172200 > [ 50.265840] which belongs to the cache kmalloc-2048 of size 2048 > [ 50.265927] The buggy address is located 1784 bytes inside of > [ 50.265927] 2048-byte region [88018e172200, 88018e172a00) > [ 50.266011] The buggy address belongs to the page: > [ 50.266089] page:ea0006385c00 count:1 mapcount:0 > mapping: index:0x0 compound_mapcount: 0 > [ 50.266178] flags: 0x17fff808100(slab|head) > [ 50.266257] raw: 017fff808100 > 0001800f000f > [ 50.266342] raw: dead0100 dead0200 8801d9016800 > > [ 50.266425] page dumped because: kasan: bad access detected > [ 50.266501] > [ 50.266590] Memory state around the buggy address: > [ 50.266693] 88018e172780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb > fb fb > [ 50.266776] 88018e172800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb > fb fb > [ 50.266860] >88018e172880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb > fb fb > [ 50.266943] > ^ > [ 50.267020] 88018e172900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb > fb fb > [ 50.267103] 88018e172980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb
