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Tue, 14 Apr 2020 12:47:23 -0700 (PDT) MIME-Version: 1.0 References: <20200407095107.1988-1-miles.chen@mediatek.com> <20200407181908.GB94792@iweiny-DESK2.sc.intel.com> In-Reply-To: <20200407181908.GB94792@iweiny-DESK2.sc.intel.com> From: Souptick Joarder Date: Wed, 15 Apr 2020 01:25:07 +0530 Message-ID: Subject: Re: [PATCH] mm/gup: fix null pointer dereference detected by coverity To: Ira Weiny Cc: Miles Chen , Andrew Morton , Linux-MM , linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, wsd_upstream@mediatek.com Content-Type: text/plain; charset="UTF-8" X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Apr 7, 2020 at 11:49 PM Ira Weiny wrote: > > On Tue, Apr 07, 2020 at 05:51:07PM +0800, Miles Chen 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); > > ... > > } > > > > Fixes: 4a9e1cda2748 ("mm: bring in additional flag for fixup_user_fault to signal unlock") > > Signed-off-by: Miles Chen > > Reviewed-by: Ira Weiny Acked-by: Souptick Joarder > > > --- > > mm/gup.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/gup.c b/mm/gup.c > > index da3e03185144..a68d11dc232d 100644 > > --- 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; > > } > > -- > > 2.18.0 >