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authorTyler Hicks <tyhicks@canonical.com>2012-01-12 11:30:44 +0100
committerTyler Hicks <tyhicks@canonical.com>2012-01-25 14:43:39 -0600
commitdb10e556518eb9d21ee92ff944530d84349684f4 (patch)
tree84a82f496a4fe4ee90812b5d7f2cd358f9730911
parentbb4503615d95d6826b7907986ad574e3157877e8 (diff)
downloadlinux-linaro-stable-db10e556518eb9d21ee92ff944530d84349684f4.tar.gz
eCryptfs: Sanitize write counts of /dev/ecryptfs
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> Cc: <stable@vger.kernel.org>
-rw-r--r--fs/ecryptfs/miscdev.c56
1 files changed, 38 insertions, 18 deletions
diff --git a/fs/ecryptfs/miscdev.c b/fs/ecryptfs/miscdev.c
index 940a82e63dc3..0dc5a3d554a4 100644
--- a/fs/ecryptfs/miscdev.c
+++ b/fs/ecryptfs/miscdev.c
@@ -409,11 +409,47 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf,
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",
@@ -435,23 +471,7 @@ ecryptfs_miscdev_write(struct file *file, const char __user *buf,
}
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);