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

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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.