Commit 71c95825 authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Peter Zijlstra

x86/unwind/orc: Fix error handling in __unwind_start()

The unwind_state 'error' field is used to inform the reliable unwinding
code that the stack trace can't be trusted.  Set this field for all
errors in __unwind_start().

Also, move the zeroing out of the unwind_state struct to before the ORC
table initialization check, to prevent the caller from reading
uninitialized data if the ORC table is corrupted.

Fixes: af085d90 ("stacktrace/x86: add function for detecting reliable stack traces")
Fixes: d3a09104 ("x86/unwinder/orc: Dont bail on stack overflow")
Fixes: 98d0c8eb ("x86/unwind/orc: Prevent unwinding before ORC initialization")
Reported-by: default avatarPavel Machek <pavel@denx.de>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/d6ac7215a84ca92b895fdd2e1aa546729417e6e6.1589487277.git.jpoimboe@redhat.com
parent 2ef96a5b
...@@ -617,23 +617,23 @@ EXPORT_SYMBOL_GPL(unwind_next_frame); ...@@ -617,23 +617,23 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task, void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame) struct pt_regs *regs, unsigned long *first_frame)
{ {
if (!orc_init)
goto done;
memset(state, 0, sizeof(*state)); memset(state, 0, sizeof(*state));
state->task = task; state->task = task;
if (!orc_init)
goto err;
/* /*
* Refuse to unwind the stack of a task while it's executing on another * Refuse to unwind the stack of a task while it's executing on another
* CPU. This check is racy, but that's ok: the unwinder has other * CPU. This check is racy, but that's ok: the unwinder has other
* checks to prevent it from going off the rails. * checks to prevent it from going off the rails.
*/ */
if (task_on_another_cpu(task)) if (task_on_another_cpu(task))
goto done; goto err;
if (regs) { if (regs) {
if (user_mode(regs)) if (user_mode(regs))
goto done; goto the_end;
state->ip = regs->ip; state->ip = regs->ip;
state->sp = regs->sp; state->sp = regs->sp;
...@@ -666,6 +666,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, ...@@ -666,6 +666,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
* generate some kind of backtrace if this happens. * generate some kind of backtrace if this happens.
*/ */
void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp); void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
state->error = true;
if (get_stack_info(next_page, state->task, &state->stack_info, if (get_stack_info(next_page, state->task, &state->stack_info,
&state->stack_mask)) &state->stack_mask))
return; return;
...@@ -691,8 +692,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, ...@@ -691,8 +692,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
return; return;
done: err:
state->error = true;
the_end:
state->stack_info.type = STACK_TYPE_UNKNOWN; state->stack_info.type = STACK_TYPE_UNKNOWN;
return;
} }
EXPORT_SYMBOL_GPL(__unwind_start); EXPORT_SYMBOL_GPL(__unwind_start);
Markdown is supported
0%
or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment