linux-kernel - [48/80] aio: check for multiplication overflow in do_io

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Message-Id: <20100924162619.052259227@clark.site>
Date:	Fri, 24 Sep 2010 09:24:36 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jeff Moyer <jmoyer@...hat.com>
Subject: [48/80] aio: check for multiplication overflow in do_io_submit

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeff Moyer <jmoyer@...hat.com>

commit 75e1c70fc31490ef8a373ea2a4bea2524099b478 upstream.

Tavis Ormandy pointed out that do_io_submit does not do proper bounds
checking on the passed-in iocb array:

       if (unlikely(nr < 0))
               return -EINVAL;

       if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(iocbpp)))))
               return -EFAULT;                      ^^^^^^^^^^^^^^^^^^

The attached patch checks for overflow, and if it is detected, the
number of iocbs submitted is scaled down to a number that will fit in
the long.  This is an ok thing to do, as sys_io_submit is documented as
returning the number of iocbs submitted, so callers should handle a
return value of less than the 'nr' argument passed in.

Reported-by: Tavis Ormandy <taviso@...xchg8b.com>
Signed-off-by: Jeff Moyer <jmoyer@...hat.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/aio.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1667,6 +1667,9 @@ long do_io_submit(aio_context_t ctx_id,
 	if (unlikely(nr < 0))
 		return -EINVAL;
 
+	if (unlikely(nr > LONG_MAX/sizeof(*iocbpp)))
+		nr = LONG_MAX/sizeof(*iocbpp);
+
 	if (unlikely(!access_ok(VERIFY_READ, iocbpp, (nr*sizeof(*iocbpp)))))
 		return -EFAULT;
 


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