From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Qian Cai <cai@lca.pw>, mpe@ellerman.id.au
Cc: linuxppc-dev@lists.ozlabs.org, rashmicy@gmail.com,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3] powerpc/64s/pgtable: fix an undefined behaviour
Date: Fri, 6 Mar 2020 07:56:06 +0100 [thread overview]
Message-ID: <952c3921-5aa8-bff5-9a87-baf5f901c535@c-s.fr> (raw)
In-Reply-To: <20200306044852.3236-1-cai@lca.pw>
Le 06/03/2020 à 05:48, Qian Cai a écrit :
> 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>
Reviewed-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
>
> v3: convert pud_index() etc to static inline functions.
> v2: convert pud_offset() etc to static inline functions.
>
> 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 201a69e6a355..bd432c6706b9 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
>
next prev parent reply other threads:[~2020-03-06 7:02 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-06 4:48 [PATCH v3] powerpc/64s/pgtable: fix an undefined behaviour Qian Cai
2020-03-06 6:56 ` Christophe Leroy [this message]
2020-05-09 13:19 ` Qian Cai
2020-06-09 5:28 ` Michael Ellerman
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