| From 3f8d197f953e758b7f4135f51267a14765105459 Mon Sep 17 00:00:00 2001 |
| From: Josh Poimboeuf <jpoimboe@redhat.com> |
| Date: Fri, 17 Jul 2020 09:04:26 -0500 |
| Subject: [PATCH] x86/stacktrace: Fix reliable check for empty user task stacks |
| |
| commit 039a7a30ec102ec866d382a66f87f6f7654f8140 upstream. |
| |
| If a user task's stack is empty, or if it only has user regs, ORC |
| reports it as a reliable empty stack. But arch_stack_walk_reliable() |
| incorrectly treats it as unreliable. |
| |
| That happens because the only success path for user tasks is inside the |
| loop, which only iterates on non-empty stacks. Generally, a user task |
| must end in a user regs frame, but an empty stack is an exception to |
| that rule. |
| |
| Thanks to commit 71c95825289f ("x86/unwind/orc: Fix error handling in |
| __unwind_start()"), unwind_start() now sets state->error appropriately. |
| So now for both ORC and FP unwinders, unwind_done() and !unwind_error() |
| always means the end of the stack was successfully reached. So the |
| success path for kthreads is no longer needed -- it can also be used for |
| empty user tasks. |
| |
| Reported-by: Wang ShaoBo <bobo.shaobowang@huawei.com> |
| Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> |
| Signed-off-by: Thomas Gleixner <tglx@linutronix.de> |
| Tested-by: Wang ShaoBo <bobo.shaobowang@huawei.com> |
| Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@redhat.com |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c |
| index 2d6898c2cb64..6d83b4b857e6 100644 |
| --- a/arch/x86/kernel/stacktrace.c |
| +++ b/arch/x86/kernel/stacktrace.c |
| @@ -58,7 +58,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, |
| * or a page fault), which can make frame pointers |
| * unreliable. |
| */ |
| - |
| if (IS_ENABLED(CONFIG_FRAME_POINTER)) |
| return -EINVAL; |
| } |
| @@ -81,10 +80,6 @@ int arch_stack_walk_reliable(stack_trace_consume_fn consume_entry, |
| if (unwind_error(&state)) |
| return -EINVAL; |
| |
| - /* Success path for non-user tasks, i.e. kthreads and idle tasks */ |
| - if (!(task->flags & (PF_KTHREAD | PF_IDLE))) |
| - return -EINVAL; |
| - |
| return 0; |
| } |
| |
| -- |
| 2.27.0 |
| |
