From mboxrd@z Thu Jan 1 00:00:00 1970 From: ard.biesheuvel@linaro.org (Ard Biesheuvel) Date: Fri, 22 Jul 2016 20:42:08 +0200 Subject: [PATCH] ARM: mm: use fully constructed struct pages for EFI pgd allocations Message-ID: <1469212928-21517-1-git-send-email-ard.biesheuvel@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The late_alloc() PTE allocation function used by create_mapping_late() does not call pgtable_page_ctor() on PTE pages it allocates, leaving the per-page spinlock uninitialized. Since generic page table manipulation code may assume that translation table pages that are not owned by init_mm are covered by fully constructed struct pages, the following crash may occur with the new UEFI memory attributes table code. efi: memattr: Processing EFI Memory Attributes table: efi: memattr: 0x0000ffa16000-0x0000ffa82fff [Runtime Code |RUN| | |XP| | | | | | | | ] Unable to handle kernel NULL pointer dereference at virtual address 00000010 pgd = c0204000 [00000010] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.7.0-rc4-00063-g3882aa7b340b #361 Hardware name: Generic DT based system task: ed858000 ti: ed842000 task.ti: ed842000 PC is at __lock_acquire+0xa0/0x19a8 ... [] (__lock_acquire) from [] (lock_acquire+0x6c/0x88) [] (lock_acquire) from [] (_raw_spin_lock+0x2c/0x3c) [] (_raw_spin_lock) from [] (apply_to_page_range+0xe8/0x238) [] (apply_to_page_range) from [] (efi_set_mapping_permissions+0x54/0x5c) [] (efi_set_mapping_permissions) from [] (efi_memattr_apply_permissions+0x2b8/0x378) [] (efi_memattr_apply_permissions) from [] (arm_enable_runtime_services+0x1f0/0x22c) [] (arm_enable_runtime_services) from [] (do_one_initcall+0x44/0x174) [] (do_one_initcall) from [] (kernel_init_freeable+0x90/0x1e8) [] (kernel_init_freeable) from [] (kernel_init+0x8/0x114) [] (kernel_init) from [] (ret_from_fork+0x14/0x24) The crash is due to the fact that the UEFI page tables are not owned by init_mm, but are not covered by fully constructed struct pages. Given that the UEFI subsystem is currently the only user of create_mapping_late(), add an unconditional call to pgtable_page_ctor() to late_alloc(). Fixes: 9fc68b717c24 ("ARM/efi: Apply strict permissions for UEFI Runtime Services regions") Signed-off-by: Ard Biesheuvel --- The commit in question was introduced in v4.7, so ideally this should go in as a late fix. However, EFI on ARM is not widely used [yet], and the memory attributes table even less so, so I am perfectly happy for this to go in later. arch/arm/mm/mmu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c index 62f4d01941f7..d0ac45451805 100644 --- a/arch/arm/mm/mmu.c +++ b/arch/arm/mm/mmu.c @@ -728,7 +728,7 @@ static void *__init late_alloc(unsigned long sz) { void *ptr = (void *)__get_free_pages(PGALLOC_GFP, get_order(sz)); - BUG_ON(!ptr); + BUG_ON(!ptr || !pgtable_page_ctor(virt_to_page(ptr))); return ptr; } -- 2.7.4