From: Josh Poimboeuf jpoimboe@redhat.com
commit 71c95825289f585014fe9741b051d32a7a916680 upstream.
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: af085d9084b4 ("stacktrace/x86: add function for detecting reliable stack traces") Fixes: d3a09104018c ("x86/unwinder/orc: Dont bail on stack overflow") Fixes: 98d0c8ebf77e ("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/d6ac7215a84ca92b895fdd2e1aa546729417e6e6.158948727... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kernel/unwind_orc.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-)
--- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -589,23 +589,23 @@ 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 = kernel_stack_pointer(regs); @@ -638,6 +638,7 @@ void __unwind_start(struct unwind_state * 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; @@ -663,8 +664,9 @@ void __unwind_start(struct unwind_state
return;
-done: +err: + state->error = true; +the_end: state->stack_info.type = STACK_TYPE_UNKNOWN; - return; } EXPORT_SYMBOL_GPL(__unwind_start);