From 3fb66a70a4ae886445743354e4b60e54058bb3ff Mon Sep 17 00:00:00 2001 From: Laurentiu Tudor Date: Thu, 16 Feb 2017 09:11:29 -0600 Subject: powerpc/booke: Fix boot crash due to null hugepd On 32-bit book-e machines, hugepd_ok() no longer takes into account null hugepd values, causing this crash at boot: Unable to handle kernel paging request for data at address 0x80000000 ... NIP [c0018378] follow_huge_addr+0x38/0xf0 LR [c001836c] follow_huge_addr+0x2c/0xf0 Call Trace: follow_huge_addr+0x2c/0xf0 (unreliable) follow_page_mask+0x40/0x3e0 __get_user_pages+0xc8/0x450 get_user_pages_remote+0x8c/0x250 copy_strings+0x110/0x390 copy_strings_kernel+0x2c/0x50 do_execveat_common+0x478/0x630 do_execve+0x2c/0x40 try_to_run_init_process+0x18/0x60 kernel_init+0xbc/0x110 ret_from_kernel_thread+0x5c/0x64 This impacts all nxp (ex-freescale) 32-bit booke platforms. This was caused by the change of hugepd_t.pd from signed to unsigned, and the update to the nohash version of hugepd_ok(). Previously hugepd_ok() could exclude all non-huge and NULL pgds using > 0, whereas now we need to explicitly check that the value is not zero and also that PD_HUGE is *clear*. This isn't protected by the pgd_none() check in __find_linux_pte_or_hugepte() because on 32-bit we use pgtable-nopud.h, which causes the pgd_none() check to be always false. Fixes: 20717e1ff526 ("powerpc/mm: Fix little-endian 4K hugetlb") Cc: stable@vger.kernel.org # v4.7+ Reported-by: Madalin-Cristian Bucur Signed-off-by: Laurentiu Tudor [mpe: Flesh out change log details.] Signed-off-by: Michael Ellerman --- arch/powerpc/include/asm/nohash/pgtable.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h index 0cd8a3852763..e5805ad78e12 100644 --- a/arch/powerpc/include/asm/nohash/pgtable.h +++ b/arch/powerpc/include/asm/nohash/pgtable.h @@ -230,7 +230,7 @@ static inline int hugepd_ok(hugepd_t hpd) return ((hpd_val(hpd) & 0x4) != 0); #else /* We clear the top bit to indicate hugepd */ - return ((hpd_val(hpd) & PD_HUGE) == 0); + return (hpd_val(hpd) && (hpd_val(hpd) & PD_HUGE) == 0); #endif } -- cgit v1.2.3