Le 05/03/2020 à 05:47, 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) 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 Fixes: 8eb07b187000 ("powerpc/mm: Dump linux pagetables") Signed-off-by: Qian Cai <cai@xxxxxx> --- Notes for maintainers: This is on the top of the linux-next commit "powerpc: add support for folded p4d page tables" which is in the Andrew's tree. arch/powerpc/mm/ptdump/ptdump.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/mm/ptdump/ptdump.c b/arch/powerpc/mm/ptdump/ptdump.c index 9d6256b61df3..b530f81398a7 100644 --- a/arch/powerpc/mm/ptdump/ptdump.c +++ b/arch/powerpc/mm/ptdump/ptdump.c @@ -279,7 +279,7 @@ static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)static void walk_pud(struct pg_state *st, p4d_t *p4d, unsigned long start){ - pud_t *pud = pud_offset(p4d, 0); + pud_t *pud = pud_offset(p4d, 0UL);
Is that the only place we have to do this ? (In 5.6-rc) I see the same in: /arch/powerpc/mm/ptdump/hashpagetable.c /arch/powerpc/kvm/book3s_64_mmu_radix.c Wouldn't it be better to: - Either cast addr to unsigned long in pud_index() macro - Or change pud_index() macro to a static inline function as x86 ? Christophe
