From 240dfe0c17a9cb17a1217d2346cc42f33920e187 Mon Sep 17 00:00:00 2001 From: Zheng Yejian Date: Tue, 11 Mar 2025 08:51:19 +0900 Subject: [PATCH] x86/unwind/orc: Fix unwind for newly forked tasks BugLink: https://bugs.launchpad.net/bugs/2101915 [ 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 Signed-off-by: Koichiro Den Signed-off-by: Stefan Bader --- 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 d00c28aaa5be..d4705a348a80 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,