Passing a NULL pointer to debugfs_create_str() leads to a NULL pointer
dereference when the debugfs file is read. Following upstream
discussions, forbid the creation of debugfs string files with NULL
pointers. Add a WARN_ON() to expose offending callers and return early.
Fixes: 9af0440ec86e ("debugfs: Implement debugfs_create_str()")
Reported-by: yangshiguang <[email protected]>
Closes: https://lore.kernel.org/lkml/2025122221-gag-malt-75ba@gregkh/
Suggested-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Gui-Dong Han <[email protected]>
---
fs/debugfs/file.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/debugfs/file.c b/fs/debugfs/file.c
index 3376ab6a519d..a941d73251b0 100644
--- a/fs/debugfs/file.c
+++ b/fs/debugfs/file.c
@@ -1127,7 +1127,7 @@ static const struct file_operations fops_str_wo = {
* directory dentry if set. If this parameter is %NULL, then the
* file will be created in the root of the debugfs filesystem.
* @value: a pointer to the variable that the file should read to and write
- * from.
+ * from. This pointer and the string it points to must not be %NULL.
*
* This function creates a file in debugfs with the given name that
* contains the value of the variable @value. If the @mode variable is so
@@ -1136,6 +1136,9 @@ static const struct file_operations fops_str_wo = {
void debugfs_create_str(const char *name, umode_t mode,
struct dentry *parent, char **value)
{
+ if (WARN_ON(!value || !*value))
+ return;
+
debugfs_create_mode_unsafe(name, mode, parent, value, &fops_str,
&fops_str_ro, &fops_str_wo);
}
--
2.43.0
