From: Davidlohr Bueso <dave@stgolabs.net>
To: Laurent Dufour <laurent.du4@free.fr>
Cc: benh@kernel.crashing.org, mpe@ellerman.id.au,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] powerpc/mm: Fix missing mmap_sem release
Date: Thu, 7 Sep 2017 13:51:46 -0700 [thread overview]
Message-ID: <20170907205146.GG17982@linux-80c1.suse> (raw)
In-Reply-To: <1504801529-15113-1-git-send-email-laurent.du4@free.fr>
On Thu, 07 Sep 2017, Laurent Dufour wrote:
>The commit b5c8f0fd595d ("powerpc/mm: Rework mm_fault_error()") reviewed
>the way the error path is managed in __do_page_fault() but it was a bit too
>agressive when handling a case by returning without releasing the mmap_sem.
>
>By the way, replacing current->mm->mmap_sem by mm->mmap_sem as mm is set to
>current->mm.
>
>Fixes: b5c8f0fd595d ("powerpc/mm: Rework mm_fault_error()")
>Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
>Signed-off-by: Laurent Dufour <laurent.du4@free.fr>
>---
> arch/powerpc/mm/fault.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
>diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>index 4797d08581ce..f799ccf37d27 100644
>--- a/arch/powerpc/mm/fault.c
>+++ b/arch/powerpc/mm/fault.c
But... here:
/*
* If we need to retry the mmap_sem has already been released,
* and if there is a fatal signal pending there is no guarantee
* that we made any progress. Handle this case first.
*/
>@@ -521,10 +521,11 @@ static int __do_page_fault(struct pt_regs *regs, unsigned long address,
> * User mode? Just return to handle the fatal exception otherwise
> * return to bad_page_fault
> */
>+ up_read(&mm->mmap_sem);
> return is_user ? 0 : SIGBUS;
> }
Per the above comment, for that case handle_mm_fault()
has already released mmap_sem. The same occurs in x86,
for example.
Thanks,
Davidlohr
next prev parent reply other threads:[~2017-09-07 20:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-07 16:25 [PATCH] powerpc/mm: Fix missing mmap_sem release Laurent Dufour
2017-09-07 20:51 ` Davidlohr Bueso [this message]
2017-09-08 7:08 ` Laurent Dufour
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