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 03cd45d ("thunderbolt: Prevent crash if non-active NVMem file is read") Signed-off-by: Nicholas Johnson <[email protected]> Cc: stable <[email protected]> Signed-off-by: Srinivas Kandagatla <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Greg Kroah-Hartman <[email protected]>
mrcsosa · Mar 19, 2020 · 3c91ef6 · 3c91ef6
1 parent 061a320
commit 3c91ef6
Showing 1 changed file with 6 additions and 0 deletions.
diff --git a/drivers/nvmem/nvmem-sysfs.c b/drivers/nvmem/nvmem-sysfs.c
@@ -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)