The following commit has been merged into the x86/urgent branch of tip: Commit-ID: 039a7a30ec102ec866d382a66f87f6f7654f8140 Gitweb: https://git.kernel.org/tip/039a7a30ec102ec866d382a66f87f6f7654f8140 Author: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> AuthorDate: Fri, 17 Jul 2020 09:04:26 -05:00 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitterDate: Wed, 22 Jul 2020 23:47:47 +02:00 x86/stacktrace: Fix reliable check for empty user task stacks 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@xxxxxxxxxx> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Tested-by: Wang ShaoBo <bobo.shaobowang@xxxxxxxxxx> Link: https://lkml.kernel.org/r/f136a4e5f019219cbc4f4da33b30c2f44fa65b84.1594994374.git.jpoimboe@xxxxxxxxxx --- arch/x86/kernel/stacktrace.c | 5 ----- 1 file changed, 5 deletions(-) diff --git a/arch/x86/kernel/stacktrace.c b/arch/x86/kernel/stacktrace.c index 6ad43fc..2fd698e 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; }
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