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From: Dan Carpenter <dan.carpenter@oracle.com>
To: Jan Harkes <jaharkes@cs.cmu.edu>
Cc: coda@cs.cmu.edu, codalist@telemann.coda.cs.cmu.edu,
	linux-fsdevel@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: [PATCH] fs/coda: potential buffer overflow in coda_psdev_write()
Date: Thu, 12 Jul 2018 15:32:56 +0300	[thread overview]
Message-ID: <20180712123255.rkcszmwdmrloxaki@kili.mountain> (raw)

"dcbuf" is a union that is "size" bytes large.  We ensure that "nbytes"
is large enough to hold the smallest member of the union, but if we
require a larger union member then then we could access beyond the end
of the allocated memory in coda_downcall().

The union is quite small so we can allocate enough space so everything
fits.  The CODA_ALLOC() macro calls kzalloc() which means the extra
memory is just zeroed and it's fine.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/fs/coda/psdev.c b/fs/coda/psdev.c
index c5234c21b539..910d57e576e2 100644
--- a/fs/coda/psdev.c
+++ b/fs/coda/psdev.c
@@ -124,7 +124,7 @@ static ssize_t coda_psdev_write(struct file *file, const char __user *buf,
 				hdr.opcode, hdr.unique);
 		        nbytes = size;
 		}
-		CODA_ALLOC(dcbuf, union outputArgs *, nbytes);
+		CODA_ALLOC(dcbuf, union outputArgs *, size);
 		if (copy_from_user(dcbuf, buf, nbytes)) {
 			CODA_FREE(dcbuf, nbytes);
 			retval = -EFAULT;

             reply	other threads:[~2018-07-12 12:43 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-07-12 12:32 Dan Carpenter [this message]
2018-07-12 15:31 ` [PATCH] fs/coda: potential buffer overflow in coda_psdev_write() Jan Harkes
2018-07-12 15:50   ` Dan Carpenter
     [not found] ` <20180713151017.lxbv4eljvd6olziq@kili.mountain>
     [not found]   ` <20180713161630.olrwa2n2tnpqbmlt@cs.cmu.edu>
2018-07-13 19:05     ` [PATCH v2] " Dan Carpenter
2018-07-13 19:08       ` Jan Harkes
2018-07-14  2:24       ` [PATCH v3] " Jan Harkes

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