staging: p9auth: prevent some oopses and memory leaks

Before all testcases, do:
	mknod /dev/caphash c 253 0
	mknod /dev/capuse c 253 1

This patch does the following:

1. caphash write of > CAP_NODE_SIZE bytes overruns node_ptr->data
	(test: cat /etc/mime.types > /dev/caphash)
2. make sure we don't dereference a NULL cap_devices[0].head
	(test: cat serge@root@abab > /dev/capuse)
3. don't let strlen dereference a NULL target_user etc
	(test: echo ab > /dev/capuse)
4. Don't leak a bunch of memory in cap_write().  Note that
   technically node_ptr is not needed for the capuse write case.
   As a result I have a much more extensive patch splitting up
   cap_write(), but I thought a smaller patch that is easier to test
   and verify would be a better start.  To test:
	cnt=0
	while [ 1 ]; do
		echo /etc/mime.types > /dev/capuse
		if [ $((cnt%25)) -eq 0 ]; then
			head -2 /proc/meminfo
		fi
		cnt=$((cnt+1))
		sleep 0.3
	done
   Without this patch, it MemFree steadily drops.  With the patch,
   it does not.

I have *not* tested this driver (with or without these patches)
with factotum or anything - only using the tests described above.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/staging/p9auth/p9auth.c b/drivers/staging/p9auth/p9auth.c
index 3cac89b..9111dcb 100644 (file)
--- a/drivers/staging/p9auth/p9auth.c
+++ b/drivers/staging/p9auth/p9auth.c
@@ -180,8 +180,12 @@ static ssize_t cap_write(struct file *filp, const char __user *buf,
        if (down_interruptible(&dev->sem))
                return -ERESTARTSYS;
 
+       user_buf_running = NULL;
+       hash_str = NULL;
        node_ptr = kmalloc(sizeof(struct cap_node), GFP_KERNEL);
        user_buf = kzalloc(count, GFP_KERNEL);
+       if (!node_ptr || !user_buf)
+               goto out;
 
        if (copy_from_user(user_buf, buf, count)) {
                retval = -EFAULT;
@@ -193,11 +197,21 @@ static ssize_t cap_write(struct file *filp, const char __user *buf,
         * hashed capability supplied by the user to the list of hashes
         */
        if (0 == iminor(filp->f_dentry->d_inode)) {
+               if (count > CAP_NODE_SIZE) {
+                       retval = -EINVAL;
+                       goto out;
+               }
                printk(KERN_INFO "Capability being written to /dev/caphash : \n");
                hexdump(user_buf, count);
                memcpy(node_ptr->data, user_buf, count);
                list_add(&(node_ptr->list), &(dev->head->list));
+               node_ptr = NULL;
        } else {
+               if (!cap_devices[0].head ||
+                               list_empty(&(cap_devices[0].head->list))) {
+                       retval = -EINVAL;
+                       goto out;
+               }
                /*
                 * break the supplied string into tokens with @ as the
                 * delimiter If the string is "user1@user2@randomstring" we
@@ -208,6 +222,10 @@ static ssize_t cap_write(struct file *filp, const char __user *buf,
                source_user = strsep(&user_buf_running, "@");
                target_user = strsep(&user_buf_running, "@");
                rand_str = strsep(&user_buf_running, "@");
+               if (!source_user || !target_user || !rand_str) {
+                       retval = -EINVAL;
+                       goto out;
+               }
 
                /* hash the string user1@user2 with rand_str as the key */
                len = strlen(source_user) + strlen(target_user) + 1;
@@ -224,7 +242,7 @@ static ssize_t cap_write(struct file *filp, const char __user *buf,
                        retval = -EFAULT;
                        goto out;
                }
-               memcpy(node_ptr->data, result, CAP_NODE_SIZE);
+               memcpy(node_ptr->data, result, CAP_NODE_SIZE);  /* why? */
                /* Change the process's uid if the hash is present in the
                 * list of hashes
                 */
@@ -299,6 +317,10 @@ static ssize_t cap_write(struct file *filp, const char __user *buf,
                dev->size = *f_pos;
 
 out:
+       kfree(node_ptr);
+       kfree(user_buf);
+       kfree(user_buf_running);
+       kfree(hash_str);
        up(&dev->sem);
        return retval;
 }