Commit e483bb9a authored Apr 23, 2021 by Mark Langsdorf Committed by Rafael J. Wysocki Apr 28, 2021

ACPI: custom_method: fix potential use-after-free issue



In cm_write(), buf is always freed when reaching the end of the
function.  If the requested count is less than table.length, the
allocated buffer will be freed but subsequent calls to cm_write() will
still try to access it.

Remove the unconditional kfree(buf) at the end of the function and
set the buf to NULL in the -EINVAL error path to match the rest of
function.

Fixes: 03d1571d ("ACPI: custom_method: fix memory leaks")
Signed-off-by: Mark Langsdorf <mlangsdo@redhat.com>
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

parent d8f9176b

drivers/acpi/custom_method.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -55,6 +55,7 @@ static ssize_t cm_write(struct file file, const char __user user_buf,
		(*ppos + count < count) \|\|
		(count > uncopied_bytes)) {
		kfree(buf);
		buf = NULL;
		return -EINVAL;
		}

		@@ -76,7 +77,6 @@ static ssize_t cm_write(struct file file, const char __user user_buf,
		add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE);
		}

		kfree(buf);
		return count;
		}