6.6-stable review patch. If anyone has any objections, please let me know.
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From: Zheng Yejian zhengyejian@huaweicloud.com
[ 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 zhengyejian@huaweicloud.com Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 7e574cf3bf8a2..7784076819de5 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,