patch "nvmem: check for NULL reg_read and reg_write before dereferencing" added to char-misc-testing

This is a note to let you know that I've just added the patch titled

nvmem: check for NULL reg_read and reg_write before dereferencing

to my char-misc git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
in the char-misc-testing branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will be merged to the char-misc-next branch sometime soon, after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.

From a263682a3c9b9ce7b57fbe0296492d1a73d8be58 Mon Sep 17 00:00:00 2001
From: Nicholas Johnson <[email protected]>
Date: Tue, 10 Mar 2020 13:22:52 +0000
Subject: nvmem: check for NULL reg_read and reg_write before dereferencing

Return -EPERM if reg_read is NULL in bin_attr_nvmem_read() or if reg_write is NULL in bin_attr_nvmem_write().

This prevents NULL dereferences such as the one described in 03cd45d2e219 ("thunderbolt: Prevent crash if non-active NVMem file is read")

---
 drivers/nvmem/nvmem-sysfs.c | 6 ++++++
 1 file changed, 6 insertions(+)

index 9e0c429cd08a..8759c4470012 100644
@@ -56,6 +56,9 @@ static ssize_t bin_attr_nvmem_read(struct file *filp, struct kobject *kobj,
 
 	count = round_down(count, nvmem->word_size);
 
+	if (!nvmem->reg_read)
+		return -EPERM;
+
 	rc = nvmem->reg_read(nvmem->priv, pos, buf, count);
 
 	if (rc)

@@ -90,6 +93,9 @@ static ssize_t bin_attr_nvmem_write(struct file *filp, struct kobject *kobj,
 
 	count = round_down(count, nvmem->word_size);
 
+	if (!nvmem->reg_write)
+		return -EPERM;
+
 	rc = nvmem->reg_write(nvmem->priv, pos, buf, count);
 
 	if (rc)

2.25.1