From 74c953ca5f6b4d5f1daa1ef34f4317e15c1a2987 Mon Sep 17 00:00:00 2001 From: Qian Cai Date: Sat, 2 Feb 2019 10:50:17 +0100 Subject: [PATCH] efi/arm64: Fix debugfs crash by adding a terminator for ptdump marker When reading 'efi_page_tables' debugfs triggers an out-of-bounds access here: arch/arm64/mm/dump.c: 282 if (addr >= st->marker[1].start_address) { called from: arch/arm64/mm/dump.c: 331 note_page(st, addr, 2, pud_val(pud)); because st->marker++ is is called after "UEFI runtime end" which is the last element in addr_marker[]. Therefore, add a terminator like the one for kernel_page_tables, so it can be skipped to print out non-existent markers. Here's the KASAN bug report: # cat /sys/kernel/debug/efi_page_tables ---[ UEFI runtime start ]--- 0x0000000020000000-0x0000000020010000 64K PTE RW NX SHD AF ... 0x0000000020200000-0x0000000021340000 17664K PTE RW NX SHD AF ... ... 0x0000000021920000-0x0000000021950000 192K PTE RW x SHD AF ... 0x0000000021950000-0x00000000219a0000 320K PTE RW NX SHD AF ... ---[ UEFI runtime end ]--- ---[ (null) ]--- ---[ (null) ]--- BUG: KASAN: global-out-of-bounds in note_page+0x1f0/0xac0 Read of size 8 at addr ffff2000123f2ac0 by task read_all/42464 Call trace: dump_backtrace+0x0/0x298 show_stack+0x24/0x30 dump_stack+0xb0/0xdc print_address_description+0x64/0x2b0 kasan_report+0x150/0x1a4 __asan_report_load8_noabort+0x30/0x3c note_page+0x1f0/0xac0 walk_pgd+0xb4/0x244 ptdump_walk_pgd+0xec/0x140 ptdump_show+0x40/0x50 seq_read+0x3f8/0xad0 full_proxy_read+0x9c/0xc0 __vfs_read+0xfc/0x4c8 vfs_read+0xec/0x208 ksys_read+0xd0/0x15c __arm64_sys_read+0x84/0x94 el0_svc_handler+0x258/0x304 el0_svc+0x8/0xc The buggy address belongs to the variable: __compound_literal.0+0x20/0x800 Memory state around the buggy address: ffff2000123f2980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff2000123f2a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa >ffff2000123f2a80: fa fa fa fa 00 00 00 00 fa fa fa fa 00 00 00 00 ^ ffff2000123f2b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff2000123f2b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 0 [ ardb: fix up whitespace ] [ mingo: fix up some moar ] Signed-off-by: Qian Cai Signed-off-by: Ard Biesheuvel Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: linux-efi@vger.kernel.org Fixes: 9d80448ac92b ("efi/arm64: Add debugfs node to dump UEFI runtime page tables") Link: http://lkml.kernel.org/r/20190202095017.13799-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar --- drivers/firmware/efi/arm-runtime.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/drivers/firmware/efi/arm-runtime.c b/drivers/firmware/efi/arm-runtime.c index 23ea1ed409d1..352bd2473162 100644 --- a/drivers/firmware/efi/arm-runtime.c +++ b/drivers/firmware/efi/arm-runtime.c @@ -37,8 +37,9 @@ extern u64 efi_system_table; static struct ptdump_info efi_ptdump_info = { .mm = &efi_mm, .markers = (struct addr_marker[]){ - { 0, "UEFI runtime start" }, - { DEFAULT_MAP_WINDOW_64, "UEFI runtime end" } + { 0, "UEFI runtime start" }, + { DEFAULT_MAP_WINDOW_64, "UEFI runtime end" }, + { -1, NULL } }, .base_addr = 0, };