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authorMark Rutland <mark.rutland@arm.com>2016-09-23 17:55:05 +0100
committerWill Deacon <will.deacon@arm.com>2016-09-26 14:24:01 +0100
commitb5e7307d9d5a340d2c9fabbe1cee137d4c682c71 (patch)
tree88d8b7c8059b0163ddb91844d1e86a901dc96b40 /arch/arm64
parent1d8f51d41fc7116f3753fe9f9a5dd93e0b550a2c (diff)
arm64: fix dump_backtrace/unwind_frame with NULL tsk
In some places, dump_backtrace() is called with a NULL tsk parameter, e.g. in bug_handler() in arch/arm64, or indirectly via show_stack() in core code. The expectation is that this is treated as if current were passed instead of NULL. Similar is true of unwind_frame(). Commit a80a0eb70c358f8c ("arm64: make irq_stack_ptr more robust") didn't take this into account. In dump_backtrace() it compares tsk against current *before* we check if tsk is NULL, and in unwind_frame() we never set tsk if it is NULL. Due to this, we won't initialise irq_stack_ptr in either function. In dump_backtrace() this results in calling dump_mem() for memory immediately above the IRQ stack range, rather than for the relevant range on the task stack. In unwind_frame we'll reject unwinding frames on the IRQ stack. In either case this results in incomplete or misleading backtrace information, but is not otherwise problematic. The initial percpu areas (including the IRQ stacks) are allocated in the linear map, and dump_mem uses __get_user(), so we shouldn't access anything with side-effects, and will handle holes safely. This patch fixes the issue by having both functions handle the NULL tsk case before doing anything else with tsk. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Fixes: a80a0eb70c358f8c ("arm64: make irq_stack_ptr more robust") Acked-by: James Morse <james.morse@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will.deacon@arm.com> Cc: Yang Shi <yang.shi@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com>
Diffstat (limited to 'arch/arm64')
-rw-r--r--arch/arm64/kernel/stacktrace.c5
-rw-r--r--arch/arm64/kernel/traps.c10
2 files changed, 9 insertions, 6 deletions
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index ca01addf8c4c..c2efddfca18c 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -43,6 +43,9 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
unsigned long fp = frame->fp;
unsigned long irq_stack_ptr;
+ if (!tsk)
+ tsk = current;
+
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
@@ -67,7 +70,7 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8));
#ifdef CONFIG_FUNCTION_GRAPH_TRACER
- if (tsk && tsk->ret_stack &&
+ if (tsk->ret_stack &&
(frame->pc == (unsigned long)return_to_handler)) {
/*
* This is a case where function graph tracer has
diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index 93445f8b530c..5ff020f8fb7f 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -142,6 +142,11 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
unsigned long irq_stack_ptr;
int skip;
+ pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
+
+ if (!tsk)
+ tsk = current;
+
/*
* Switching between stacks is valid when tracing current and in
* non-preemptible context.
@@ -151,11 +156,6 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
else
irq_stack_ptr = 0;
- pr_debug("%s(regs = %p tsk = %p)\n", __func__, regs, tsk);
-
- if (!tsk)
- tsk = current;
-
if (tsk == current) {
frame.fp = (unsigned long)__builtin_frame_address(0);
frame.sp = current_stack_pointer;