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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: af085d9084 ("stacktrace/x86: add function for detecting reliable stack traces")
Fixes: d3a0910401 ("x86/unwinder/orc: Dont bail on stack overflow")
Fixes: 98d0c8ebf7 ("x86/unwind/orc: Prevent unwinding before ORC initialization")
Reported-by: Pavel Machek <pavel@denx.de>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/d6ac7215a84ca92b895fdd2e1aa546729417e6e6.1589487277.git.jpoimboe@redhat.com
This commit is contained in:
Josh Poimboeuf 2020-05-14 15:31:10 -05:00 committed by Peter Zijlstra
parent 2ef96a5bb1
commit 71c9582528
1 changed files with 9 additions and 7 deletions
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16
arch/x86/kernel/unwind_orc.c
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@ -617,23 +617,23 @@ EXPORT_SYMBOL_GPL(unwind_next_frame);
void __unwind_start(struct unwind_state *state, struct task_struct *task,
struct pt_regs *regs, unsigned long *first_frame)
{
if (!orc_init)
goto done;
memset(state, 0, sizeof(*state));
state->task = task;
if (!orc_init)
goto err;
/*
* 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
* checks to prevent it from going off the rails.
*/
if (task_on_another_cpu(task))
goto done;
goto err;
if (regs) {
if (user_mode(regs))
goto done;
goto the_end;
state->ip = regs->ip;
state->sp = regs->sp;
@ -666,6 +666,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
* generate some kind of backtrace if this happens.
*/
void *next_page = (void *)PAGE_ALIGN((unsigned long)state->sp);
state->error = true;
if (get_stack_info(next_page, state->task, &state->stack_info,
&state->stack_mask))
return;
@ -691,8 +692,9 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task,
return;
done:
err:
state->error = true;
the_end:
state->stack_info.type = STACK_TYPE_UNKNOWN;
return;
}
EXPORT_SYMBOL_GPL(__unwind_start);