Commits
Qian Cai committed 74c953ca5f6
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 <cai@lca.pw>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
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 <mingo@kernel.org>