Re: FAILED: patch "[PATCH] arm64: hugetlb: avoid potential NULL dereference" failed to apply to 4.9-stable tree

[Sasha Levin <sashal@kernel.org>]

On Wed, May 13, 2020 at 01:21:20PM +0200, Greg Kroah-Hartman wrote:
>On Wed, May 13, 2020 at 11:35:45AM +0100, Will Deacon wrote:
>> [+Sasha, as I think he did the backport]
>>
>> On Wed, May 13, 2020 at 04:02:09PM +0530, Naresh Kamboju wrote:
>> > On Tue, 12 May 2020 at 16:56, <gregkh@linuxfoundation.org> wrote:
>> > >
>> > >
>> > > The patch below does not apply to the 4.9-stable tree.
>> > > If someone wants it applied there, or to any other stable or longterm
>> > > tree, then please email the backport, including the original git commit
>> > > id to <stable@vger.kernel.org>.
>> > >
>> > > thanks,
>> > >
>> > > greg k-h
>> > >
>> > > ------------------ original commit in Linus's tree ------------------
>> > >
>> > > From 027d0c7101f50cf03aeea9eebf484afd4920c8d3 Mon Sep 17 00:00:00 2001
>> > > From: Mark Rutland <mark.rutland@arm.com>
>> > > Date: Tue, 5 May 2020 13:59:30 +0100
>> > > Subject: [PATCH] arm64: hugetlb: avoid potential NULL dereference
>> > > MIME-Version: 1.0
>> > > Content-Type: text/plain; charset=UTF-8
>> > > Content-Transfer-Encoding: 8bit
>> > >
>> > > The static analyzer in GCC 10 spotted that in huge_pte_alloc() we may
>> > > pass a NULL pmdp into pte_alloc_map() when pmd_alloc() returns NULL:
>> > >
>> > > |   CC      arch/arm64/mm/pageattr.o
>> > > |   CC      arch/arm64/mm/hugetlbpage.o
>> > > |                  from arch/arm64/mm/hugetlbpage.c:10:
>> > > | arch/arm64/mm/hugetlbpage.c: In function ‘huge_pte_alloc’:
>> > > | ./arch/arm64/include/asm/pgtable-types.h:28:24: warning: dereference of NULL ‘pmdp’ [CWE-690] [-Wanalyzer-null-dereference]
>> > > | ./arch/arm64/include/asm/pgtable.h:436:26: note: in expansion of macro ‘pmd_val’
>> > > | arch/arm64/mm/hugetlbpage.c:242:10: note: in expansion of macro ‘pte_alloc_map’
>> > > |     |arch/arm64/mm/hugetlbpage.c:232:10:
>> > > |     |./arch/arm64/include/asm/pgtable-types.h:28:24:
>> > > | ./arch/arm64/include/asm/pgtable.h:436:26: note: in expansion of macro ‘pmd_val’
>> > > | arch/arm64/mm/hugetlbpage.c:242:10: note: in expansion of macro ‘pte_alloc_map’
>> > >
>> > > This can only occur when the kernel cannot allocate a page, and so is
>> > > unlikely to happen in practice before other systems start failing.
>> > >
>> > > We can avoid this by bailing out if pmd_alloc() fails, as we do earlier
>> > > in the function if pud_alloc() fails.
>> > >
>> > > Fixes: 66b3923a1a0f ("arm64: hugetlb: add support for PTE contiguous bit")
>> > > Signed-off-by: Mark Rutland <mark.rutland@arm.com>
>> > > Reported-by: Kyrill Tkachov <kyrylo.tkachov@arm.com>
>> > > Cc: <stable@vger.kernel.org> # 4.5.x-
>> > > Cc: Will Deacon <will@kernel.org>
>> > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
>> > >
>> > > diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
>> > > index bbeb6a5a6ba6..0be3355e3499 100644
>> > > --- a/arch/arm64/mm/hugetlbpage.c
>> > > +++ b/arch/arm64/mm/hugetlbpage.c
>> > > @@ -230,6 +230,8 @@ pte_t *huge_pte_alloc(struct mm_struct *mm,
>> > >                 ptep = (pte_t *)pudp;
>> > >         } else if (sz == (CONT_PTE_SIZE)) {
>> > >                 pmdp = pmd_alloc(mm, pudp, addr);
>> > > +               if (!pmdp)
>> > > +                       return NULL;
>> > >
>> > >                 WARN_ON(addr & (sz - 1));
>> > >                 /*
>> > >
>> >
>> > on stable-rc 4.9 branch arm64 architecture build failed.
>> >
>> >   CC      arch/arm64/mm/hugetlbpage.o
>> > arch/arm64/mm/hugetlbpage.c: In function 'huge_pte_alloc':
>> > arch/arm64/mm/hugetlbpage.c:106:8: error: 'pmdp' undeclared (first use
>> > in this function); did you mean 'pmd'?
>> >    if (!pmdp)
>> >         ^~~~
>> >         pmd
>> > arch/arm64/mm/hugetlbpage.c:106:8: note: each undeclared identifier is
>> > reported only once for each function it appears in
>> > scripts/Makefile.build:304: recipe for target
>> > 'arch/arm64/mm/hugetlbpage.o' failed
>> >
>> > ref:
>> > https://ci.linaro.org/view/lkft/job/openembedded-lkft-linux-stable-rc-4.9/DISTRO=lkft,MACHINE=hikey,label=docker-lkft/893/consoleText
>
>Now dropped from 4.9 as well.

'pmdp' -> 'pmd' Argh :(

-- 
Thanks,
Sasha