From: Andrew Morton <akpm@linux-foundation.org>
To: Miles Chen <miles.chen@mediatek.com>
Cc: linux-mm@kvack.org, Peter Xu <peterx@redhat.com>,
linux-mediatek@lists.infradead.org, linux-kernel@vger.kernel.org,
wsd_upstream@mediatek.com
Subject: Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity
Date: Tue, 14 Apr 2020 17:08:27 -0700 [thread overview]
Message-ID: <20200414170827.d32fc1fc12a33b140b740b94@linux-foundation.org> (raw)
In-Reply-To: <20200407095107.1988-1-miles.chen@mediatek.com>
On Tue, 7 Apr 2020 17:51:07 +0800 Miles Chen <miles.chen@mediatek.com> wrote:
> In fixup_user_fault(), it is possible that unlocked is NULL,
> so we should test unlocked before using it.
>
> For example, in arch/arc/kernel/process.c, NULL is passed
> to fixup_user_fault().
>
> SYSCALL_DEFINE3(arc_usr_cmpxchg, int *, uaddr, int, expected, int, new)
> {
> ...
> ret = fixup_user_fault(current, current->mm, (unsigned long) uaddr,
> FAULT_FLAG_WRITE, NULL);
> ...
> }
(cc Peter)
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -1230,7 +1230,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm,
> if (ret & VM_FAULT_RETRY) {
> down_read(&mm->mmap_sem);
> if (!(fault_flags & FAULT_FLAG_TRIED)) {
> - *unlocked = true;
> + if (unlocked)
> + *unlocked = true;
> fault_flags |= FAULT_FLAG_TRIED;
> goto retry;
> }
Not sure. If the caller passes FAULT_FLAG_ALLOW_RETRY then they must
also pass in a valid non-NULL `unlocked'. If the caller passed
FAULT_FLAG_ALLOW_RETRY and unlocked==NULL then the resulting oops is an
appropriate way of reporting this mistake. I think?
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next prev parent reply other threads:[~2020-04-15 0:08 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-07 9:51 [PATCH] mm/gup: fix null pointer dereference detected by coverity Miles Chen
2020-04-07 18:19 ` Ira Weiny
2020-04-14 19:55 ` Souptick Joarder
2020-04-15 0:08 ` Andrew Morton [this message]
2020-04-15 1:53 ` Miles Chen
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