From: ard.biesheuvel@linaro.org (Ard Biesheuvel)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] arm64: kernel: restrict /dev/mem read() calls to linear region
Date: Wed, 12 Apr 2017 09:26:06 +0100 [thread overview]
Message-ID: <20170412082606.17151-1-ard.biesheuvel@linaro.org> (raw)
When running lscpu on an AArch64 system that has SMBIOS version 2.0
tables, it will segfault in the following way:
Unable to handle kernel paging request at virtual address ffff8000bfff0000
pgd = ffff8000f9615000
[ffff8000bfff0000] *pgd=0000000000000000
Internal error: Oops: 96000007 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 1284 Comm: lscpu Not tainted 4.11.0-rc3+ #103
Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
task: ffff8000fa78e800 task.stack: ffff8000f9780000
PC is at __arch_copy_to_user+0x90/0x220
LR is at read_mem+0xcc/0x140
This is caused by the fact that lspci issues a read() on /dev/mem at the
offset where it expects to find the SMBIOS structure array. However, this
region is classified as EFI_RUNTIME_SERVICE_DATA (as per the UEFI spec),
and so it is omitted from the linear mapping.
So let's restrict /dev/mem read/write access to those areas that are
covered by the linear region.
Reported-by: Alexander Graf <agraf@suse.de>
Fixes: 4dffbfc48d65 ("arm64/efi: mark UEFI reserved regions as MEMBLOCK_NOMAP")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/arm64/mm/mmap.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/arch/arm64/mm/mmap.c b/arch/arm64/mm/mmap.c
index 7b0d55756eb1..2956240d17d7 100644
--- a/arch/arm64/mm/mmap.c
+++ b/arch/arm64/mm/mmap.c
@@ -18,6 +18,7 @@
#include <linux/elf.h>
#include <linux/fs.h>
+#include <linux/memblock.h>
#include <linux/mm.h>
#include <linux/mman.h>
#include <linux/export.h>
@@ -103,12 +104,8 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
*/
int valid_phys_addr_range(phys_addr_t addr, size_t size)
{
- if (addr < PHYS_OFFSET)
- return 0;
- if (addr + size > __pa(high_memory - 1) + 1)
- return 0;
-
- return 1;
+ return memblock_is_map_memory(addr) &&
+ memblock_is_map_memory(addr + size - 1);
}
/*
--
2.9.3
next reply other threads:[~2017-04-12 8:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-12 8:26 Ard Biesheuvel [this message]
2017-04-12 8:29 ` [PATCH] arm64: kernel: restrict /dev/mem read() calls to linear region Alexander Graf
2017-04-12 8:31 ` Ard Biesheuvel
2017-04-25 16:46 ` Will Deacon
2017-04-12 8:33 ` Domenico Andreoli
2017-04-12 9:29 ` Russell King - ARM Linux
2017-04-12 9:37 ` Ard Biesheuvel
2017-04-12 12:44 ` Domenico Andreoli
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