coda: potential buffer overflow in coda_psdev_write()

Add checks to make sure the downcall message we got from the Coda cache
manager is large enough to contain the data it is supposed to have.
i.e.  when we get a CODA_ZAPDIR we can access &out->coda_zapdir.CodaFid.

Link: http://lkml.kernel.org/r/894fb6b250add09e4e3935f14649f21284a5cb18.1558117389.git.jaharkes@cs.cmu.edu
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Cc: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/coda/psdev.c b/fs/coda/psdev.c
index 241f7e04ad04..b4da2812499e 100644
--- a/fs/coda/psdev.c
+++ b/fs/coda/psdev.c
@@ -100,8 +100,12 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
         ssize_t retval = 0, count = 0;
         int error;
 
+        /* make sure there is enough to copy out the (opcode, unique) values */
+        if (nbytes < (2 * sizeof(u_int32_t)))
+                return -EINVAL;
+
         /* Peek at the opcode, uniquefier */
-        if (copy_from_user(&hdr, buf, 2 * sizeof(u_long)))
+        if (copy_from_user(&hdr, buf, 2 * sizeof(u_int32_t)))
                 return -EFAULT;
 
         if (DOWNCALL(hdr.opcode)) {
@@ -127,7 +131,7 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
                 }
 
                 /* what downcall errors does Venus handle ? */
-                error = coda_downcall(vcp, hdr.opcode, dcbuf);
+                error = coda_downcall(vcp, hdr.opcode, dcbuf, nbytes);
 
                 CODA_FREE(dcbuf, nbytes);
                 if (error) {