Patch "fgraph: Fix missing unlock in register_ftrace_graph()" has been added to the 6.11-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    fgraph: Fix missing unlock in register_ftrace_graph()

to the 6.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fgraph-fix-missing-unlock-in-register_ftrace_graph.patch
and it can be found in the queue-6.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 7b72fdf4ccc307bc325ed13074eaff146ebe1c43
Author: Li Huafei <lihuafei1@xxxxxxxxxx>
Date:   Thu Oct 24 23:59:17 2024 +0800

    fgraph: Fix missing unlock in register_ftrace_graph()
    
    [ Upstream commit bd3734db86e01e20dd239a40b419059a0ce9c901 ]
    
    Use guard(mutex)() to acquire and automatically release ftrace_lock,
    fixing the issue of not unlocking when calling cpuhp_setup_state()
    fails.
    
    Fixes smatch warning:
    
    kernel/trace/fgraph.c:1317 register_ftrace_graph() warn: inconsistent returns '&ftrace_lock'.
    
    Link: https://lore.kernel.org/20241024155917.1019580-1-lihuafei1@xxxxxxxxxx
    Fixes: 2c02f7375e65 ("fgraph: Use CPU hotplug mechanism to initialize idle shadow stacks")
    Reported-by: kernel test robot <lkp@xxxxxxxxx>
    Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
    Closes: https://lore.kernel.org/r/202410220121.wxg0olfd-lkp@xxxxxxxxx/
    Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
    Signed-off-by: Li Huafei <lihuafei1@xxxxxxxxxx>
    Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
    Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/trace/fgraph.c b/kernel/trace/fgraph.c
index 41e7a15dcb50c..cd1c2946018c8 100644
--- a/kernel/trace/fgraph.c
+++ b/kernel/trace/fgraph.c
@@ -1252,7 +1252,7 @@ int register_ftrace_graph(struct fgraph_ops *gops)
 	int ret = 0;
 	int i = -1;
 
-	mutex_lock(&ftrace_lock);
+	guard(mutex)(&ftrace_lock);
 
 	if (!fgraph_initialized) {
 		ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "fgraph_idle_init",
@@ -1273,10 +1273,8 @@ int register_ftrace_graph(struct fgraph_ops *gops)
 	}
 
 	i = fgraph_lru_alloc_index();
-	if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub)) {
-		ret = -ENOSPC;
-		goto out;
-	}
+	if (i < 0 || WARN_ON_ONCE(fgraph_array[i] != &fgraph_stub))
+		return -ENOSPC;
 	gops->idx = i;
 
 	ftrace_graph_active++;
@@ -1313,8 +1311,6 @@ int register_ftrace_graph(struct fgraph_ops *gops)
 		gops->saved_func = NULL;
 		fgraph_lru_release_index(i);
 	}
-out:
-	mutex_unlock(&ftrace_lock);
 	return ret;
 }