Subject: Re: Test patch for KASAN: global-out-of-bounds Read in detach_capi_ctr

From: Greg KH <[email-masked]>
Date: Tue, 5 Jul 2022 07:18:36 +0200

On Mon, Jul 04, 2022 at 09:59:38PM -0700, Soumya Negi wrote:
> On Mon, Jul 04, 2022 at 01:54:17PM +0200, Greg KH wrote:
> > On Mon, Jul 04, 2022 at 02:26:19PM +0300, Dan Carpenter wrote:
> > > 
> > > On Fri, Jul 01, 2022 at 06:08:29AM -0700, Soumya Negi wrote:
> > > > #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
> > > > 3f8a27f9e27bd78604c0709224cec0ec85a8b106
> > > > 
> > > > -- 
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> > > 
> > > > From 3aa5aaffef64a5574cbdb3f5c985bc25b612140c Mon Sep 17 00:00:00 2001
> > > > From: Soumya Negi <[email-masked]>
> > > > Date: Fri, 1 Jul 2022 04:52:17 -0700
> > > > Subject: [PATCH] isdn: capi: Add check for controller count in
> > > >  detach_capi_ctr()
> > > > 
> > > > Fixes Syzbot bug:
> > > > https://syzkaller.appspot.com/bug?id=14f4820fbd379105a71fdee357b0759b90587a4e
> > > > 
> > > > This patch checks whether any ISDN devices are registered before unregistering
> > > > a CAPI controller(device). Without the check, the controller struct capi_str
> > > > results in out-of-bounds access bugs to other CAPI data strucures in
> > > > detach_capri_ctr() as seen in the bug report.
> > > > 
> > > 
> > > This bug was already fixed by commit 1f3e2e97c003 ("isdn: cpai: check
> > > ctr->cnr to avoid array index out of bound").
> > > 
> > > It just needs to be backported.  Unfortunately there was no Fixes tag so
> > > it wasn't picked up.  Also I'm not sure how backports work in netdev.
> > 
> > That commit has already been backported quite a while ago and is in the
> > following releases:
> > 	4.4.290 4.9.288 4.14.253 4.19.214 5.4.156 5.10.76 5.14.15 5.15
> > 
> 
> Thanks for letting me know. Is there a way I can check whether an open
> syzbot bug already has a fix as in this case? Right now I am thinking
> of running the reproducer on linux-next as well before starting on a
> bug.

Always run the reproducer first if for no other reason than to be able
to test if you do fix a problem or not.  You can also always have syzbot
run it too, use the email interface to it for that.

good luck!

greg k-h