Re: [PATCH -next v2] powerpc/64s/pgtable: fix an undefined behaviour
From: Christophe Leroy <hidden>
Date: 2020-03-05 19:22:26
Also in:
linux-mm, lkml
Le 05/03/2020 à 15:32, 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_offset() and friends to static inline functions.
I was suggesting to convert pud_index() to static inline, because that's where the shift sits. Is it not possible ? Here you seems to fix the problem for now, but if someone reuses pud_index() in another macro one day, the same problem may happen again. Christophe
quoted hunk ↗ jump to hunk
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 <redacted> Signed-off-by: Qian Cai <redacted> --- arch/powerpc/include/asm/book3s/64/pgtable.h | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index fa60e8594b9f..4967bc9e25e2 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h@@ -1016,12 +1016,20 @@ static inline bool p4d_access_permitted(p4d_t p4d, bool write) #define pgd_offset(mm, address) ((mm)->pgd + pgd_index(address)) -#define pud_offset(p4dp, addr) \ - (((pud_t *) p4d_page_vaddr(*(p4dp))) + pud_index(addr)) -#define pmd_offset(pudp,addr) \ - (((pmd_t *) pud_page_vaddr(*(pudp))) + pmd_index(addr)) -#define pte_offset_kernel(dir,addr) \ - (((pte_t *) pmd_page_vaddr(*(dir))) + pte_index(addr)) +static inline pud_t *pud_offset(p4d_t *p4d, unsigned long address) +{ + return (pud_t *)p4d_page_vaddr(*p4d) + pud_index(address); +} + +static inline pmd_t *pmd_offset(pud_t *pud, unsigned long address) +{ + return (pmd_t *)pud_page_vaddr(*pud) + pmd_index(address); +} + +static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address) +{ + return (pte_t *)pmd_page_vaddr(*pmd) + pte_index(address); +} #define pte_offset_map(dir,addr) pte_offset_kernel((dir), (addr))