[for-linus][PATCH 2/2] tracing: Prevent bad count for tracing_cpumask_write

[Steven Rostedt]

From: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>

If a large count is provided, it will trigger a warning in bitmap_parse_user.
Also check zero for it.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9e01c1b74c953 ("cpumask: convert kernel trace functions")
Link: https://lore.kernel.org/20241216073238.2573704-1-lizhi.xu@xxxxxxxxxxxxx
Reported-by: syzbot+0aecfd34fb878546f3fd@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=0aecfd34fb878546f3fd
Tested-by: syzbot+0aecfd34fb878546f3fd@xxxxxxxxxxxxxxxxxxxxxxxxx
Signed-off-by: Lizhi Xu <lizhi.xu@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
---
 kernel/trace/trace.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 957f941a08e7..f8aebcb01e62 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5087,6 +5087,9 @@ tracing_cpumask_write(struct file *filp, const char __user *ubuf,
 	cpumask_var_t tracing_cpumask_new;
 	int err;
 
+	if (count == 0 || count > KMALLOC_MAX_SIZE)
+		return -EINVAL;
+
 	if (!zalloc_cpumask_var(&tracing_cpumask_new, GFP_KERNEL))
 		return -ENOMEM;
 
-- 
2.45.2