• Mark Rutland's avatar
    arm64: hugetlb: avoid potential NULL dereference · 027d0c71
    Mark Rutland authored
    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: 66b3923a ("arm64: hugetlb: add support for PTE contiguous bit")
    Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
    Reported-by: default avatarKyrill Tkachov <kyrylo.tkachov@arm.com>
    Cc: <stable@vger.kernel.org> # 4.5.x-
    Cc: Will Deacon <will@kernel.org>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    027d0c71
hugetlbpage.c 10.9 KB