Patch "coda: fix 'kernel memory exposure attempt' in fsync" has been added to the 4.13-stable tree

Patch "coda: fix 'kernel memory exposure attempt' in fsync" has been added to the 4.13-stable tree

[gregkh]

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

    coda: fix 'kernel memory exposure attempt' in fsync

to the 4.13-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     coda-fix-kernel-memory-exposure-attempt-in-fsync.patch
and it can be found in the queue-4.13 subdirectory.

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


>From d337b66a4c52c7b04eec661d86c2ef6e168965a2 Mon Sep 17 00:00:00 2001
From: Jan Harkes <jaharkes@cs.cmu.edu>
Date: Wed, 27 Sep 2017 15:52:12 -0400
Subject: coda: fix 'kernel memory exposure attempt' in fsync

From: Jan Harkes <jaharkes@cs.cmu.edu>

commit d337b66a4c52c7b04eec661d86c2ef6e168965a2 upstream.

When an application called fsync on a file in Coda a small request with
just the file identifier was allocated, but the declared length was set
to the size of union of all possible upcall requests.

This bug has been around for a very long time and is now caught by the
extra checking in usercopy that was introduced in Linux-4.8.

The exposure happens when the Coda cache manager process reads the fsync
upcall request at which point it is killed. As a result there is nobody
servicing any further upcalls, trapping any processes that try to access
the mounted Coda filesystem.

Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/coda/upcall.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

--- a/fs/coda/upcall.c
+++ b/fs/coda/upcall.c
@@ -446,8 +446,7 @@ int venus_fsync(struct super_block *sb,
 	UPARG(CODA_FSYNC);
 
 	inp->coda_fsync.VFid = *fid;
-	error = coda_upcall(coda_vcp(sb), sizeof(union inputArgs),
-			    &outsize, inp);
+	error = coda_upcall(coda_vcp(sb), insize, &outsize, inp);
 
 	CODA_FREE(inp, insize);
 	return error;


Patches currently in stable-queue which might be from jaharkes@cs.cmu.edu are

queue-4.13/coda-fix-kernel-memory-exposure-attempt-in-fsync.patch