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>

3 files changed, 41 insertions, 4 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) {
diff --git a/fs/coda/upcall.c b/fs/coda/upcall.c
index 1175a1722411..cf1e662681a5 100644
--- a/fs/coda/upcall.c
+++ b/fs/coda/upcall.c
@@ -804,12 +804,44 @@ exit:
  *
  * CODA_REPLACE -- replace one CodaFid with another throughout the name cache */
 
-int coda_downcall(struct venus_comm *vcp, int opcode, union outputArgs *out)
+int coda_downcall(struct venus_comm *vcp, int opcode, union outputArgs *out,
+                  size_t nbytes)
 {
         struct inode *inode = NULL;
         struct CodaFid *fid = NULL, *newfid;
         struct super_block *sb;
 
+        /*
+         * Make sure we have received enough data from the cache
+         * manager to populate the necessary fields in the buffer
+         */
+        switch (opcode) {
+        case CODA_PURGEUSER:
+                if (nbytes < sizeof(struct coda_purgeuser_out))
+                        return -EINVAL;
+                break;
+
+        case CODA_ZAPDIR:
+                if (nbytes < sizeof(struct coda_zapdir_out))
+                        return -EINVAL;
+                break;
+
+        case CODA_ZAPFILE:
+                if (nbytes < sizeof(struct coda_zapfile_out))
+                        return -EINVAL;
+                break;
+
+        case CODA_PURGEFID:
+                if (nbytes < sizeof(struct coda_purgefid_out))
+                        return -EINVAL;
+                break;
+
+        case CODA_REPLACE:
+                if (nbytes < sizeof(struct coda_replace_out))
+                        return -EINVAL;
+                break;
+        }
+
         /* Handle invalidation requests. */
         mutex_lock(&vcp->vc_mutex);
         sb = vcp->vc_sb;
diff --git a/include/linux/coda_psdev.h b/include/linux/coda_psdev.h
index 57d2b2faf6a3..d1672fd5e638 100644
--- a/include/linux/coda_psdev.h
+++ b/include/linux/coda_psdev.h
@@ -71,7 +71,8 @@ int venus_symlink(struct super_block *sb, struct CodaFid *fid,
 int venus_access(struct super_block *sb, struct CodaFid *fid, int mask);
 int venus_pioctl(struct super_block *sb, struct CodaFid *fid,
                  unsigned int cmd, struct PioctlData *data);
-int coda_downcall(struct venus_comm *vcp, int opcode, union outputArgs *out);
+int coda_downcall(struct venus_comm *vcp, int opcode, union outputArgs *out,
+                  size_t nbytes);
 int venus_fsync(struct super_block *sb, struct CodaFid *fid);
 int venus_statfs(struct dentry *dentry, struct kstatfs *sfs);