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debugfs: check for NULL pointer in debugfs_create_str()

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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: 9af0440ec8 ("debugfs: Implement debugfs_create_str()")
Reported-by: yangshiguang <yangshiguang@xiaomi.com>
Closes: https://lore.kernel.org/lkml/2025122221-gag-malt-75ba@gregkh/
Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Gui-Dong Han <hanguidong02@gmail.com>
Link: https://patch.msgid.link/20260323085930.88894-2-hanguidong02@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Gui-Dong Han
2026-03-23 16:58:44 +08:00
committed by Greg Kroah-Hartman
parent 56e3ee721b
commit 31de83980d
1 changed files with 4 additions and 1 deletions
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5
fs/debugfs/file.c
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@@ -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);
}