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>

1 files changed, 23 insertions, 1 deletions

diff --git a/drivers/staging/p9auth/p9auth.c b/drivers/staging/p9auth/p9auth.c
index 3cac89b26faf..9111dcba37a1 100644
--- 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;
 }