From c7365330753c55a061db0a1837a27fd5e44b1408 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Sat, 22 Jul 2017 12:48:34 +0100 Subject: arm64: unwind: disregard frame.sp when validating frame pointer Currently, when unwinding the call stack, we validate the frame pointer of each frame against frame.sp, whose value is not clearly defined, and which makes it more difficult to link stack frames together across different stacks. It is far better to simply check whether the frame pointer itself points into a valid stack. Signed-off-by: Ard Biesheuvel Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: James Morse Cc: Will Deacon --- arch/arm64/include/asm/irq.h | 10 +++++++++- arch/arm64/kernel/stacktrace.c | 24 +++++++----------------- 2 files changed, 16 insertions(+), 18 deletions(-) diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h index 6d6f85e4923e..8155e486ce48 100644 --- a/arch/arm64/include/asm/irq.h +++ b/arch/arm64/include/asm/irq.h @@ -7,6 +7,7 @@ #ifndef __ASSEMBLER__ #include +#include #include #include @@ -49,12 +50,19 @@ static inline int nr_legacy_irqs(void) static inline bool on_irq_stack(unsigned long sp) { - /* variable names the same as kernel/stacktrace.c */ unsigned long low = (unsigned long)raw_cpu_ptr(irq_stack); unsigned long high = low + IRQ_STACK_START_SP; return (low <= sp && sp <= high); } +static inline bool on_task_stack(struct task_struct *tsk, unsigned long sp) +{ + unsigned long low = (unsigned long)task_stack_page(tsk); + unsigned long high = low + THREAD_SIZE; + + return (low <= sp && sp < high); +} + #endif /* !__ASSEMBLER__ */ #endif diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c index 6ffb965be641..beaf51fb3088 100644 --- a/arch/arm64/kernel/stacktrace.c +++ b/arch/arm64/kernel/stacktrace.c @@ -42,9 +42,10 @@ */ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) { - unsigned long high, low; unsigned long fp = frame->fp; - unsigned long irq_stack_ptr; + + if (fp & 0xf) + return -EINVAL; if (!tsk) tsk = current; @@ -53,19 +54,8 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) * Switching between stacks is valid when tracing current and in * non-preemptible context. */ - if (tsk == current && !preemptible()) - irq_stack_ptr = IRQ_STACK_PTR(); - else - irq_stack_ptr = 0; - - low = frame->sp; - /* irq stacks are not THREAD_SIZE aligned */ - if (on_irq_stack(frame->sp)) - high = irq_stack_ptr; - else - high = ALIGN(low, THREAD_SIZE) - 0x20; - - if (fp < low || fp > high || fp & 0xf) + if (!(tsk == current && !preemptible() && on_irq_stack(fp)) && + !on_task_stack(tsk, fp)) return -EINVAL; frame->sp = fp + 0x10; @@ -94,9 +84,9 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame) * Check the frame->fp we read from the bottom of the irq_stack, * and the original task stack pointer are both in current->stack. */ - if (frame->sp == irq_stack_ptr) { + if (frame->sp == IRQ_STACK_PTR()) { struct pt_regs *irq_args; - unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(irq_stack_ptr); + unsigned long orig_sp = IRQ_STACK_TO_TASK_STACK(frame->sp); if (object_is_on_stack((void *)orig_sp) && object_is_on_stack((void *)frame->fp)) { -- cgit v1.2.3-59-g8ed1b