Re: [syzbot] KASAN: use-after-free Read in r871xu_dev_remove

[Pavel Skripkin <paskripkin@gmail.com>]

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On Tue, 13 Jul 2021 17:04:28 +0800
Dongliang Mu <mudongliangabcd@gmail.com> wrote:

> On Tue, Jul 13, 2021 at 4:55 PM Pavel Skripkin <paskripkin@gmail.com>
> wrote:
> >
> > On Mon, 12 Jul 2021 20:14:24 -0700
> > syzbot <syzbot+5872a520e0ce0a7c7230@syzkaller.appspotmail.com>
> > wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit:    92510a7f Add linux-next specific files for
> > > 20210709 git tree:       linux-next
> > > console output:
> > > https://syzkaller.appspot.com/x/log.txt?x=16c50180300000 kernel
> > > config:
> > > https://syzkaller.appspot.com/x/.config?x=505de2716f052686
> > > dashboard link:
> > > https://syzkaller.appspot.com/bug?extid=5872a520e0ce0a7c7230 syz
> > > repro: https://syzkaller.appspot.com/x/repro.syz?x=1639a73c300000
> > > C reproducer:
> > > https://syzkaller.appspot.com/x/repro.c?x=15fcd5e4300000
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to
> > > the commit: Reported-by:
> > > syzbot+5872a520e0ce0a7c7230@syzkaller.appspotmail.com
> > >
> >
> > Hmm, bisection is wrong this time. It should be
> > e02a3b945816 ("staging: rtl8712: fix memory leak in
> > rtl871x_load_fw_cb")
> 
> Hi Paval,
> 
    ^^^^^
    Pavel :)

> can you share more details about why the patch e02a3b945816 causes
> this UAF problem?
> 

I am not sure, but I think, that free_netdev() call rigth after
complete() can cause use-after-free bug in wait_for_completion() since
rtl8712_fw_ready is allocated as netdev private data.

I guess, schedule() call after complete() can help here.


BTW, I send wrong patch in previous email: typo in schedule() :)

#syz test:
git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master




> >
> > #syz test:
> > git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> > master
> >
> >
> > I guess, this should work
> >
> >
> > With regards,
> > Pavel Skripkin
> >
> > --
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> > discussion on the web visit
> > https://groups.google.com/d/msgid/syzkaller-bugs/20210713115546.34c99ea8%40gmail.com.




With regards,
Pavel Skripkin

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From 4c25accd0fc806687142aadeaa5b19805289ac74 Mon Sep 17 00:00:00 2001
From: Pavel Skripkin <paskripkin@gmail.com>
Date: Tue, 13 Jul 2021 11:52:17 +0300
Subject: [PATCH] staging: rtl8712: fix UAF in r871xu_dev_remove

/* .... */

Signed-off-by: Pavel Skripkin <paskripkin@gmail.com>
---
 drivers/staging/rtl8712/hal_init.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/staging/rtl8712/hal_init.c b/drivers/staging/rtl8712/hal_init.c
index 22974277afa0..e81c66cc8580 100644
--- a/drivers/staging/rtl8712/hal_init.c
+++ b/drivers/staging/rtl8712/hal_init.c
@@ -43,6 +43,7 @@ static void rtl871x_load_fw_cb(const struct firmware *firmware, void *context)
 		r8712_free_drv_sw(adapter);
 		adapter->dvobj_deinit(adapter);
 		complete(&adapter->rtl8712_fw_ready);
+		schedule();				/* to not trigger UAF in wait_for_completion() */
 		free_netdev(adapter->pnetdev);
 		return;
 	}
-- 
2.32.0