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From: Andrew Morton <akpm@linux-foundation.org>
To: Wang Cheng <wanngchenng@gmail.com>
Cc: linux-mm@kvack.org, cgroups@vger.kernel.org,
	linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com,
	syzbot+ad1b8c404f0959c4bfcc@syzkaller.appspotmail.com
Subject: Re: [PATCH] mm/mempolicy: fix uninit-value in mpol_rebind_policy()
Date: Tue, 17 May 2022 17:08:17 -0700	[thread overview]
Message-ID: <20220517170817.94ca21558bbe035ae06bf6fa@linux-foundation.org> (raw)
In-Reply-To: <20220516094726.b5rrsjg7rvei2od5@ppc.localdomain>

On Mon, 16 May 2022 17:47:26 +0800 Wang Cheng <wanngchenng@gmail.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@syzkaller.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 ;)


WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
To: Wang Cheng <wanngchenng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org,
	cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	syzkaller-bugs-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org,
	syzbot+ad1b8c404f0959c4bfcc-Pl5Pbv+GP7P466ipTTIvnc23WoclnBCfAL8bYrjMMd8@public.gmane.org
Subject: Re: [PATCH] mm/mempolicy: fix uninit-value in mpol_rebind_policy()
Date: Tue, 17 May 2022 17:08:17 -0700	[thread overview]
Message-ID: <20220517170817.94ca21558bbe035ae06bf6fa@linux-foundation.org> (raw)
In-Reply-To: <20220516094726.b5rrsjg7rvei2od5-EN706goElQQmYvmMESoHnA@public.gmane.org>

On Mon, 16 May 2022 17:47:26 +0800 Wang Cheng <wanngchenng-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> 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-Pl5Pbv+GP7P466ipTTIvnc23WoclnBCfAL8bYrjMMd8@public.gmane.org
> 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 ;)


  reply	other threads:[~2022-05-18  0:08 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-12 12:34 [PATCH] mm/mempolicy: fix uninit-value in mpol_rebind_policy() Wang Cheng
2022-05-12 12:34 ` Wang Cheng
2022-05-16  9:47 ` Wang Cheng
2022-05-16  9:47   ` Wang Cheng
2022-05-18  0:08   ` Andrew Morton [this message]
2022-05-18  0:08     ` Andrew Morton
2022-05-18  8:52     ` Dmitry Vyukov
2022-05-18  8:52       ` Dmitry Vyukov

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