This is a note to let you know that I've just added the patch titled ACPI: custom_method: fix a possible memory leak to the 5.11-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: acpi-custom_method-fix-a-possible-memory-leak.patch and it can be found in the queue-5.11 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 1cfd8956437f842836e8a066b40d1ec2fc01f13e Mon Sep 17 00:00:00 2001 From: Mark Langsdorf <mlangsdo@xxxxxxxxxx> Date: Tue, 27 Apr 2021 13:54:33 -0500 Subject: ACPI: custom_method: fix a possible memory leak From: Mark Langsdorf <mlangsdo@xxxxxxxxxx> commit 1cfd8956437f842836e8a066b40d1ec2fc01f13e upstream. In cm_write(), if the 'buf' is allocated memory but not fully consumed, it is possible to reallocate the buffer without freeing it by passing '*ppos' as 0 on a subsequent call. Add an explicit kfree() before kzalloc() to prevent the possible memory leak. Fixes: 526b4af47f44 ("ACPI: Split out custom_method functionality into an own driver") Signed-off-by: Mark Langsdorf <mlangsdo@xxxxxxxxxx> Cc: 5.4+ <stable@xxxxxxxxxxxxxxx> # 5.4+ Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/acpi/custom_method.c | 2 ++ 1 file changed, 2 insertions(+) --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -42,6 +42,8 @@ static ssize_t cm_write(struct file *fil sizeof(struct acpi_table_header))) return -EFAULT; uncopied_bytes = max_size = table.length; + /* make sure the buf is not allocated */ + kfree(buf); buf = kzalloc(max_size, GFP_KERNEL); if (!buf) return -ENOMEM; Patches currently in stable-queue which might be from mlangsdo@xxxxxxxxxx are queue-5.11/acpi-custom_method-fix-a-possible-memory-leak.patch queue-5.11/acpi-custom_method-fix-potential-use-after-free-issue.patch