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Message-ID: <CACT4Y+ZkDJmoaT5ks8cmhzaNhhgaLYAhvzx+5q3yzKQEW1LZ5A@mail.gmail.com>
Date: Wed, 18 May 2022 10:52:51 +0200
From: Dmitry Vyukov <dvyukov@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Wang Cheng <wanngchenng@...il.com>, linux-mm@...ck.org,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
syzkaller-bugs@...glegroups.com,
syzbot+ad1b8c404f0959c4bfcc@...kaller.appspotmail.com
Subject: Re: [PATCH] mm/mempolicy: fix uninit-value in mpol_rebind_policy()
On Wed, 18 May 2022 at 02:08, Andrew Morton <akpm@...ux-foundation.org> wrote:
>
> On Mon, 16 May 2022 17:47:26 +0800 Wang Cheng <wanngchenng@...il.com> wrote:
>
> >
> > ...
> >
> > This patch seems to fix below bug too.
> > KMSAN: uninit-value in mpol_rebind_mm (2)
> > https://syzkaller.appspot.com/bug?id=f2fecd0d7013f54ec4162f60743a2b28df40926b
> >
> > The uninit-value is pol->w.cpuset_mems_allowed in mpol_rebind_policy().
> > When syzkaller reproducer runs to the beginning of mpol_new(),
> >
> > mpol_new() mm/mempolicy.c
> > do_mbind() mm/mempolicy.c
> > kernel_mbind() mm/mempolicy.c
> >
> > `mode` is 1(MPOL_PREFERRED), nodes_empty(*nodes) is `true` and `flags`
> > is 0. Then
> >
> > mode = MPOL_LOCAL;
> > ...
> > policy->mode = mode;
> > policy->flags = flags;
> >
> > will be executed. So in mpol_set_nodemask(),
> >
> > mpol_set_nodemask() mm/mempolicy.c
> > do_mbind()
> > kernel_mbind()
> >
> > pol->mode is 4(MPOL_LOCAL), that `nodemask` in `pol` is not initialized,
> > which will be accessed in mpol_rebind_policy().
>
> Thanks, I added the above to the changelog and I plan to import the
> result into mm-stable later this week.
>
> > IIUC, "#syz fix: mm/mempolicy: fix uninit-value in mpol_rebind_policy()"
> > could be sent to syzbot+ad1b8c404f0959c4bfcc@...kaller.appspotmail.com
> > to attach the fixing commit to the bug. WDYT?
>
> Could be. The "syz fix" isn't a thing I've paid much attention to.
> I'll start doing so ;)
Yes, we can send:
#syz fix: mm/mempolicy: fix uninit-value in mpol_rebind_policy()
to syzbot+ad1b8c404f0959c4bfcc@...kaller.appspotmail.com
and now it should be reflected at:
https://syzkaller.appspot.com/bug?extid=ad1b8c404f0959c4bfcc
and the bug will be closed when the fix is merged everywhere.
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