pstore: add vmalloc error check

If vmalloc fails, make write_pmsg return -ENOMEM.
Signed-off-by: NGeliang Tang <geliangtang@163.com>
Acked-by: NKees Cook <keescook@chromium.org>
Signed-off-by: NTony Luck <tony.luck@intel.com>

fs/pstore/pmsg.c

@@ -37,6 +37,8 @@ static ssize_t write_pmsg(struct file *file, const char __user *buf,
 	if (buffer_size > PMSG_MAX_BOUNCE_BUFFER_SIZE)
 		buffer_size = PMSG_MAX_BOUNCE_BUFFER_SIZE;
 	buffer = vmalloc(buffer_size);
+	if (!buffer)
+		return -ENOMEM;
 
 	mutex_lock(&pmsg_lock);
 	for (i = 0; i < count; ) {