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    Subject[PATCH 5.4 168/314] powerpc/64s/pgtable: fix an undefined behaviour
    Date
    From: Qian Cai <cai@lca.pw>

    [ Upstream commit c2e929b18cea6cbf71364f22d742d9aad7f4677a ]

    Booting a power9 server with hash MMU could trigger an undefined
    behaviour because pud_offset(p4d, 0) will do,

    0 >> (PAGE_SHIFT:16 + PTE_INDEX_SIZE:8 + H_PMD_INDEX_SIZE:10)

    Fix it by converting pud_index() and friends to static inline
    functions.

    UBSAN: shift-out-of-bounds in arch/powerpc/mm/ptdump/ptdump.c:282:15
    shift exponent 34 is too large for 32-bit type 'int'
    CPU: 6 PID: 1 Comm: swapper/0 Not tainted 5.6.0-rc4-next-20200303+ #13
    Call Trace:
    dump_stack+0xf4/0x164 (unreliable)
    ubsan_epilogue+0x18/0x78
    __ubsan_handle_shift_out_of_bounds+0x160/0x21c
    walk_pagetables+0x2cc/0x700
    walk_pud at arch/powerpc/mm/ptdump/ptdump.c:282
    (inlined by) walk_pagetables at arch/powerpc/mm/ptdump/ptdump.c:311
    ptdump_check_wx+0x8c/0xf0
    mark_rodata_ro+0x48/0x80
    kernel_init+0x74/0x194
    ret_from_kernel_thread+0x5c/0x74

    Suggested-by: Christophe Leroy <christophe.leroy@c-s.fr>
    Signed-off-by: Qian Cai <cai@lca.pw>
    Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
    Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
    Link: https://lore.kernel.org/r/20200306044852.3236-1-cai@lca.pw
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    arch/powerpc/include/asm/book3s/64/pgtable.h | 23 ++++++++++++++++----
    1 file changed, 19 insertions(+), 4 deletions(-)

    diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
    index a143d394ff46f..e1eb8aa9cfbbb 100644
    --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
    +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
    @@ -998,10 +998,25 @@ extern struct page *pgd_page(pgd_t pgd);
    #define pud_page_vaddr(pud) __va(pud_val(pud) & ~PUD_MASKED_BITS)
    #define pgd_page_vaddr(pgd) __va(pgd_val(pgd) & ~PGD_MASKED_BITS)

    -#define pgd_index(address) (((address) >> (PGDIR_SHIFT)) & (PTRS_PER_PGD - 1))
    -#define pud_index(address) (((address) >> (PUD_SHIFT)) & (PTRS_PER_PUD - 1))
    -#define pmd_index(address) (((address) >> (PMD_SHIFT)) & (PTRS_PER_PMD - 1))
    -#define pte_index(address) (((address) >> (PAGE_SHIFT)) & (PTRS_PER_PTE - 1))
    +static inline unsigned long pgd_index(unsigned long address)
    +{
    + return (address >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1);
    +}
    +
    +static inline unsigned long pud_index(unsigned long address)
    +{
    + return (address >> PUD_SHIFT) & (PTRS_PER_PUD - 1);
    +}
    +
    +static inline unsigned long pmd_index(unsigned long address)
    +{
    + return (address >> PMD_SHIFT) & (PTRS_PER_PMD - 1);
    +}
    +
    +static inline unsigned long pte_index(unsigned long address)
    +{
    + return (address >> PAGE_SHIFT) & (PTRS_PER_PTE - 1);
    +}

    /*
    * Find an entry in a page-table-directory. We combine the address region
    --
    2.25.1


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