[stable:PATCH 1/2] arm64: kernel: Save and restore addr_limit on exception entry
From: James Morse <james.morse@arm.com>
Date: 2016-08-12 18:11:29
commit e19a6ee2460bdd0d0055a6029383422773f9999a upstream. If we take an exception while at EL1, the exception handler inherits the original context's addr_limit value. To be consistent always reset addr_limit and PSTATE.UAO on (re-)entry to EL1. This prevents accidental re-use of the original context's addr_limit. Based on a similar patch for arm from Russell King. Acked-by: Will Deacon <redacted> Reviewed-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: James Morse <james.morse@arm.com> Signed-off-by: Will Deacon <redacted> [ backport to stop perf misusing inherited addr_limit. Removed code interacting with UAO and the irqstack ] Link: https://bugs.chromium.org/p/project-zero/issues/detail?id=822 Signed-off-by: James Morse <james.morse@arm.com> Cc: <redacted> #4.1 --- arch/arm64/include/asm/ptrace.h | 2 ++ arch/arm64/kernel/asm-offsets.c | 1 + arch/arm64/kernel/entry.S | 15 ++++++++++++++- 3 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index d4264bb0a409..31f7344c503b 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h@@ -116,6 +116,8 @@ struct pt_regs { }; u64 orig_x0; u64 syscallno; + u64 orig_addr_limit; + u64 unused; // maintain 16 byte alignment }; #define arch_has_single_step() (1)
diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index da675cc5dfae..4106ac64f95e 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c@@ -58,6 +58,7 @@ int main(void) DEFINE(S_PC, offsetof(struct pt_regs, pc)); DEFINE(S_ORIG_X0, offsetof(struct pt_regs, orig_x0)); DEFINE(S_SYSCALLNO, offsetof(struct pt_regs, syscallno)); + DEFINE(S_ORIG_ADDR_LIMIT, offsetof(struct pt_regs, orig_addr_limit)); DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs)); BLANK(); DEFINE(MM_CONTEXT_ID, offsetof(struct mm_struct, context.id));
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index bddd04d031db..05012cdb555f 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S@@ -27,6 +27,7 @@ #include <asm/cpufeature.h> #include <asm/errno.h> #include <asm/esr.h> +#include <asm/memory.h> #include <asm/thread_info.h> #include <asm/unistd.h>
@@ -93,7 +94,13 @@ disable_step_tsk x19, x20 // exceptions when scheduling. .else add x21, sp, #S_FRAME_SIZE - .endif + get_thread_info tsk + /* Save the task's original addr_limit and set USER_DS (TASK_SIZE_64) */ + ldr x20, [tsk, #TI_ADDR_LIMIT] + str x20, [sp, #S_ORIG_ADDR_LIMIT] + mov x20, #TASK_SIZE_64 + str x20, [tsk, #TI_ADDR_LIMIT] + .endif /* \el == 0 */ mrs x22, elr_el1 mrs x23, spsr_el1 stp lr, x21, [sp, #S_LR]
@@ -117,6 +124,12 @@ .endm .macro kernel_exit, el, ret = 0 + .if \el != 0 + /* Restore the task's original addr_limit. */ + ldr x20, [sp, #S_ORIG_ADDR_LIMIT] + str x20, [tsk, #TI_ADDR_LIMIT] + .endif + ldp x21, x22, [sp, #S_PC] // load ELR, SPSR .if \el == 0 ct_user_enter
--
2.8.0.rc3