From: Mark Rutland mark.rutland@arm.com
commit 027d0c7101f50cf03aeea9eebf484afd4920c8d3 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/arm64/mm/hugetlbpage.c | 2 ++ 1 file changed, 2 insertions(+)
--- a/arch/arm64/mm/hugetlbpage.c +++ b/arch/arm64/mm/hugetlbpage.c @@ -218,6 +218,8 @@ pte_t *huge_pte_alloc(struct mm_struct * ptep = (pte_t *)pudp; } else if (sz == (PAGE_SIZE * CONT_PTES)) { pmdp = pmd_alloc(mm, pudp, addr); + if (!pmdp) + return NULL;
WARN_ON(addr & (sz - 1)); /*