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authorArd Biesheuvel <ard.biesheuvel@linaro.org>2017-04-17 11:32:01 +0200
committerIngo Molnar <mingo@kernel.org>2017-04-17 12:35:33 +0200
commit197decefdb79d6f1350ba0316ce26ba737372d0c (patch)
tree79d32c8ebc3515cf7de726694105b3aa0d203ca1 /drivers/firmware/efi/libstub
parentef/libstub/arm/arm64: Randomize the base of the UEFI rt services region (diff)
downloadlinux-197decefdb79d6f1350ba0316ce26ba737372d0c.tar.xz
linux-197decefdb79d6f1350ba0316ce26ba737372d0c.zip
efi/libstub/arm: Don't use TASK_SIZE when randomizing the RT space
As reported by James, Catalin and Mark, commit: e69176d68d26 ("ef/libstub/arm/arm64: Randomize the base of the UEFI rt services region") ... results in a crash in the firmware, regardless of whether KASLR is in effect or not and whether the firmware implements EFI_RNG_PROTOCOL or not. Mark has identified the root cause to be the inappropriate use of TASK_SIZE in the stub, which arm64 defines as: #define TASK_SIZE (test_thread_flag(TIF_32BIT) ? \ TASK_SIZE_32 : TASK_SIZE_64) and testing thread flags at this point results in the dereference of pointers in uninitialized structures. So instead, introduce a preprocessor symbol EFI_RT_VIRTUAL_LIMIT and define it to TASK_SIZE_64 on arm64 and TASK_SIZE on ARM, both of which are compile time constants. Also, change the 'headroom' variable to static const to force an error if this might change in the future. Tested-by: Mark Rutland <mark.rutland@arm.com> Tested-by: James Morse <james.morse@arm.com> Tested-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Matt Fleming <matt@codeblueprint.co.uk> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-arm-kernel@lists.infradead.org Cc: linux-efi@vger.kernel.org Link: http://lkml.kernel.org/r/20170417093201.10181-2-ard.biesheuvel@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'drivers/firmware/efi/libstub')
-rw-r--r--drivers/firmware/efi/libstub/arm-stub.c11
1 files changed, 9 insertions, 2 deletions
diff --git a/drivers/firmware/efi/libstub/arm-stub.c b/drivers/firmware/efi/libstub/arm-stub.c
index 1e45ec51b094..8181ac179d14 100644
--- a/drivers/firmware/efi/libstub/arm-stub.c
+++ b/drivers/firmware/efi/libstub/arm-stub.c
@@ -32,6 +32,12 @@
#define EFI_RT_VIRTUAL_BASE SZ_512M
#define EFI_RT_VIRTUAL_SIZE SZ_512M
+#ifdef CONFIG_ARM64
+# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE_64
+#else
+# define EFI_RT_VIRTUAL_LIMIT TASK_SIZE
+#endif
+
static u64 virtmap_base = EFI_RT_VIRTUAL_BASE;
efi_status_t efi_open_volume(efi_system_table_t *sys_table_arg,
@@ -236,8 +242,9 @@ unsigned long efi_entry(void *handle, efi_system_table_t *sys_table,
* shift of 21 bit positions into account when scaling
* the headroom value using a 32-bit random value.
*/
- u64 headroom = TASK_SIZE - EFI_RT_VIRTUAL_BASE -
- EFI_RT_VIRTUAL_SIZE;
+ static const u64 headroom = EFI_RT_VIRTUAL_LIMIT -
+ EFI_RT_VIRTUAL_BASE -
+ EFI_RT_VIRTUAL_SIZE;
u32 rnd;
status = efi_get_random_bytes(sys_table, sizeof(rnd),