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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-08-18 18:42:30 +0100
committerWill Deacon <will.deacon@arm.com>2017-08-22 18:15:42 +0100
commit4a23e56ad6549d0b8c0fac6d9eb752884379c391 (patch)
treebe09ef1ef45c2eeede655b2b5f51623e99910cc7 /arch/arm64/kernel
parentarm64: mm: abort uaccess retries upon fatal signal (diff)
downloadlinux-dev-4a23e56ad6549d0b8c0fac6d9eb752884379c391.tar.xz
linux-dev-4a23e56ad6549d0b8c0fac6d9eb752884379c391.zip
arm64: kaslr: ignore modulo offset when validating virtual displacement
In the KASLR setup routine, we ensure that the early virtual mapping of the kernel image does not cover more than a single table entry at the level above the swapper block level, so that the assembler routines involved in setting up this mapping can remain simple. In this calculation we add the proposed KASLR offset to the values of the _text and _end markers, and reject it if they would end up falling in different swapper table sized windows. However, when taking the addresses of _text and _end, the modulo offset (the physical displacement modulo 2 MB) is already accounted for, and so adding it again results in incorrect results. So disregard the modulo offset from the calculation. Fixes: 08cdac619c81 ("arm64: relocatable: deal with physically misaligned ...") Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Tested-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r--arch/arm64/kernel/head.S1
-rw-r--r--arch/arm64/kernel/kaslr.c12
2 files changed, 9 insertions, 4 deletions
diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 973df7de7bf8..adb0910b88f5 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -354,7 +354,6 @@ __primary_switched:
tst x23, ~(MIN_KIMG_ALIGN - 1) // already running randomized?
b.ne 0f
mov x0, x21 // pass FDT address in x0
- mov x1, x23 // pass modulo offset in x1
bl kaslr_early_init // parse FDT for KASLR options
cbz x0, 0f // KASLR disabled? just proceed
orr x23, x23, x0 // record KASLR offset
diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
index a9710efb8c01..1d95c204186b 100644
--- a/arch/arm64/kernel/kaslr.c
+++ b/arch/arm64/kernel/kaslr.c
@@ -75,7 +75,7 @@ extern void *__init __fixmap_remap_fdt(phys_addr_t dt_phys, int *size,
* containing function pointers) to be reinitialized, and zero-initialized
* .bss variables will be reset to 0.
*/
-u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset)
+u64 __init kaslr_early_init(u64 dt_phys)
{
void *fdt;
u64 seed, offset, mask, module_range;
@@ -133,9 +133,15 @@ u64 __init kaslr_early_init(u64 dt_phys, u64 modulo_offset)
* boundary (for 4KB/16KB/64KB granule kernels, respectively). If this
* happens, increase the KASLR offset by the size of the kernel image
* rounded up by SWAPPER_BLOCK_SIZE.
+ *
+ * NOTE: The references to _text and _end below will already take the
+ * modulo offset (the physical displacement modulo 2 MB) into
+ * account, given that the physical placement is controlled by
+ * the loader, and will not change as a result of the virtual
+ * mapping we choose.
*/
- if ((((u64)_text + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT) !=
- (((u64)_end + offset + modulo_offset) >> SWAPPER_TABLE_SHIFT)) {
+ if ((((u64)_text + offset) >> SWAPPER_TABLE_SHIFT) !=
+ (((u64)_end + offset) >> SWAPPER_TABLE_SHIFT)) {
u64 kimg_sz = _end - _text;
offset = (offset + round_up(kimg_sz, SWAPPER_BLOCK_SIZE))
& mask;