[34-longterm 135/260] aio: check for multiplication overflow in do_io_submit

Paul Gortmaker
2011-01-02T07:23:56Z

From: Jeff Moyer <jmoyer@redhat.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@cmpxchg8b.com>
Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
---
fs/aio.c | 3 +++
1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 48fdeeb..94b6cd6 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1659,6 +1659,9 @@ long do_io_submit(aio_context_t ctx_id, long nr,
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;

--
1.7.3.3