summaryrefslogtreecommitdiffstats
path: root/arch/x86/kernel/unwind_frame.c
diff options
context:
space:
mode:
Diffstat (limited to 'arch/x86/kernel/unwind_frame.c')
-rw-r--r--arch/x86/kernel/unwind_frame.c30
1 files changed, 28 insertions, 2 deletions
diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c
index 4443e499f279..23d15565d02a 100644
--- a/arch/x86/kernel/unwind_frame.c
+++ b/arch/x86/kernel/unwind_frame.c
@@ -6,6 +6,21 @@
#define FRAME_HEADER_SIZE (sizeof(long) * 2)
+/*
+ * This disables KASAN checking when reading a value from another task's stack,
+ * since the other task could be running on another CPU and could have poisoned
+ * the stack in the meantime.
+ */
+#define READ_ONCE_TASK_STACK(task, x) \
+({ \
+ unsigned long val; \
+ if (task == current) \
+ val = READ_ONCE(x); \
+ else \
+ val = READ_ONCE_NOCHECK(x); \
+ val; \
+})
+
static void unwind_dump(struct unwind_state *state, unsigned long *sp)
{
static bool dumped_before = false;
@@ -48,7 +63,8 @@ unsigned long unwind_get_return_address(struct unwind_state *state)
if (state->regs && user_mode(state->regs))
return 0;
- addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, *addr_p,
+ addr = READ_ONCE_TASK_STACK(state->task, *addr_p);
+ addr = ftrace_graph_ret_addr(state->task, &state->graph_idx, addr,
addr_p);
return __kernel_text_address(addr) ? addr : 0;
@@ -162,7 +178,7 @@ bool unwind_next_frame(struct unwind_state *state)
if (state->regs)
next_bp = (unsigned long *)state->regs->bp;
else
- next_bp = (unsigned long *)*state->bp;
+ next_bp = (unsigned long *)READ_ONCE_TASK_STACK(state->task,*state->bp);
/* is the next frame pointer an encoded pointer to pt_regs? */
regs = decode_frame_pointer(next_bp);
@@ -207,6 +223,16 @@ bool unwind_next_frame(struct unwind_state *state)
return true;
bad_address:
+ /*
+ * When unwinding a non-current task, the task might actually be
+ * running on another CPU, in which case it could be modifying its
+ * stack while we're reading it. This is generally not a problem and
+ * can be ignored as long as the caller understands that unwinding
+ * another task will not always succeed.
+ */
+ if (state->task != current)
+ goto the_end;
+
if (state->regs) {
printk_deferred_once(KERN_WARNING
"WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n",
OpenPOWER on IntegriCloud