From 8d91bdca2f97fa7a195b7a5f7552ffb6d259dda5 Mon Sep 17 00:00:00 2001 From: Zheng Yejian Date: Fri, 13 Sep 2024 10:45:01 +0800 Subject: [PATCH] x86/unwind/orc: Fix unwind for newly forked tasks [ Upstream commit 3bf19a0fb690022ec22ce87a5afeb1030cbcb56c ] When arch_stack_walk_reliable() is called to unwind for newly forked tasks, the return value is negative which means the call stack is unreliable. This obviously does not meet expectations. The root cause is that after commit 3aec4ecb3d1f ("x86: Rewrite ret_from_fork() in C"), the 'ret_addr' of newly forked task is changed to 'ret_from_fork_asm' (see copy_thread()), then at the start of the unwind, it is incorrectly interprets not as a "signal" one because 'ret_from_fork' is still used to determine the initial "signal" (see __unwind_start()). Then the address gets incorrectly decremented in the call to orc_find() (see unwind_next_frame()) and resulting in the incorrect ORC data. To fix it, check 'ret_from_fork_asm' rather than 'ret_from_fork' in __unwind_start(). Fixes: 3aec4ecb3d1f ("x86: Rewrite ret_from_fork() in C") Signed-off-by: Zheng Yejian Signed-off-by: Josh Poimboeuf Signed-off-by: Sasha Levin --- arch/x86/kernel/unwind_orc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c index 7e574cf3bf8a..7784076819de 100644 --- a/arch/x86/kernel/unwind_orc.c +++ b/arch/x86/kernel/unwind_orc.c @@ -723,7 +723,7 @@ void __unwind_start(struct unwind_state *state, struct task_struct *task, state->sp = task->thread.sp + sizeof(*frame); state->bp = READ_ONCE_NOCHECK(frame->bp); state->ip = READ_ONCE_NOCHECK(frame->ret_addr); - state->signal = (void *)state->ip == ret_from_fork; + state->signal = (void *)state->ip == ret_from_fork_asm; } if (get_stack_info((unsigned long *)state->sp, state->task,