Patch "eCryptfs: Sanitize write counts of /dev/ecryptfs" has been added to the 2.6.32-longterm tree

Patch "eCryptfs: Sanitize write counts of /dev/ecryptfs" has been added to the 2.6.32-longterm tree

[gregkh]

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

    eCryptfs: Sanitize write counts of /dev/ecryptfs

to the 2.6.32-longterm tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/longterm/longterm-queue-2.6.32.git;a=summary

The filename of the patch is:
     ecryptfs-sanitize-write-counts-of-dev-ecryptfs.patch
and it can be found in the queue-2.6.32 subdirectory.

If you, or anyone else, feels it should not be added to the 2.6.32 longterm tree,
please let <stable@vger.kernel.org> know about it.


>From db10e556518eb9d21ee92ff944530d84349684f4 Mon Sep 17 00:00:00 2001
From: Tyler Hicks <tyhicks@canonical.com>
Date: Thu, 12 Jan 2012 11:30:44 +0100
Subject: eCryptfs: Sanitize write counts of /dev/ecryptfs

From: Tyler Hicks <tyhicks@canonical.com>

commit db10e556518eb9d21ee92ff944530d84349684f4 upstream.

A malicious count value specified when writing to /dev/ecryptfs may
result in a a very large kernel memory allocation.

This patch peeks at the specified packet payload size, adds that to the
size of the packet headers and compares the result with the write count
value. The resulting maximum memory allocation size is approximately 532
bytes.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Reported-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/ecryptfs/miscdev.c |   56 +++++++++++++++++++++++++++++++++-----------------
 1 file changed, 38 insertions(+), 18 deletions(-)

--- a/fs/ecryptfs/miscdev.c
+++ b/fs/ecryptfs/miscdev.c
@@ -408,11 +408,47 @@ ecryptfs_miscdev_write(struct file *file
 	ssize_t sz = 0;
 	char *data;
 	uid_t euid = current_euid();
+	unsigned char packet_size_peek[3];
 	int rc;
 
-	if (count == 0)
+	if (count == 0) {
 		goto out;
+	} else if (count == (1 + 4)) {
+		/* Likely a harmless MSG_HELO or MSG_QUIT - no packet length */
+		goto memdup;
+	} else if (count < (1 + 4 + 1)
+		   || count > (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
+			       + ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES)) {
+		printk(KERN_WARNING "%s: Acceptable packet size range is "
+		       "[%d-%lu], but amount of data written is [%zu].",
+		       __func__, (1 + 4 + 1),
+		       (1 + 4 + 2 + sizeof(struct ecryptfs_message) + 4
+			+ ECRYPTFS_MAX_ENCRYPTED_KEY_BYTES), count);
+		return -EINVAL;
+	}
+
+	if (copy_from_user(packet_size_peek, (buf + 1 + 4),
+			   sizeof(packet_size_peek))) {
+		printk(KERN_WARNING "%s: Error while inspecting packet size\n",
+		       __func__);
+		return -EFAULT;
+	}
 
+	rc = ecryptfs_parse_packet_length(packet_size_peek, &packet_size,
+					  &packet_size_length);
+	if (rc) {
+		printk(KERN_WARNING "%s: Error parsing packet length; "
+		       "rc = [%d]\n", __func__, rc);
+		return rc;
+	}
+
+	if ((1 + 4 + packet_size_length + packet_size) != count) {
+		printk(KERN_WARNING "%s: Invalid packet size [%zu]\n", __func__,
+		       packet_size);
+		return -EINVAL;
+	}
+
+memdup:
 	data = memdup_user(buf, count);
 	if (IS_ERR(data)) {
 		printk(KERN_ERR "%s: memdup_user returned error [%ld]\n",
@@ -434,23 +470,7 @@ ecryptfs_miscdev_write(struct file *file
 		}
 		memcpy(&counter_nbo, &data[i], 4);
 		seq = be32_to_cpu(counter_nbo);
-		i += 4;
-		rc = ecryptfs_parse_packet_length(&data[i], &packet_size,
-						  &packet_size_length);
-		if (rc) {
-			printk(KERN_WARNING "%s: Error parsing packet length; "
-			       "rc = [%d]\n", __func__, rc);
-			goto out_free;
-		}
-		i += packet_size_length;
-		if ((1 + 4 + packet_size_length + packet_size) != count) {
-			printk(KERN_WARNING "%s: (1 + packet_size_length([%zd])"
-			       " + packet_size([%zd]))([%zd]) != "
-			       "count([%zd]). Invalid packet format.\n",
-			       __func__, packet_size_length, packet_size,
-			       (1 + packet_size_length + packet_size), count);
-			goto out_free;
-		}
+		i += 4 + packet_size_length;
 		rc = ecryptfs_miscdev_response(&data[i], packet_size,
 					       euid, current_user_ns(),
 					       task_pid(current), seq);


Patches currently in longterm-queue-2.6.32 which might be from tyhicks@canonical.com are

/home/gregkh/linux/longterm/longterm-queue-2.6.32/queue-2.6.32/ecryptfs-sanitize-write-counts-of-dev-ecryptfs.patch
/home/gregkh/linux/longterm/longterm-queue-2.6.32/queue-2.6.32/ecryptfs-make-truncate-path-killable.patch
/home/gregkh/linux/longterm/longterm-queue-2.6.32/queue-2.6.32/ecryptfs-improve-metadata-read-failure-logging.patch