Re: [PATCH] libceph: use 64-bit arithmetic instead of 32-bit

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Hello Ilya,

Quoting Ilya Dryomov <idryomov@xxxxxxxxx>:

On Wed, Jan 31, 2018 at 6:29 AM, Gustavo A. R. Silva
<gustavo@xxxxxxxxxxxxxx> wrote:
Cast objsetno to u64 in order to give the compiler complete
information about the proper arithmetic to use. Notice
that this variable is used in a context that expects an
expression of type u64 (64 bits, unsigned).

The expression objsetno * sc + stripepos is currently
being evaluated using 32-bit arithmetic.

In general, the use of incorrect arithmetic has security
implications.

Addresses-Coverity-ID: 200686
Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
---
 net/ceph/osdmap.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ceph/osdmap.c b/net/ceph/osdmap.c
index 0da27c6..58dc965 100644
--- a/net/ceph/osdmap.c
+++ b/net/ceph/osdmap.c
@@ -2183,7 +2183,7 @@ int ceph_calc_file_object_mapping(struct ceph_file_layout *layout,
        stripepos = bl % sc;
        objsetno = stripeno / su_per_object;

-       *ono = objsetno * sc + stripepos;
+       *ono = (u64)objsetno * sc + stripepos;
dout("objset %u * sc %u = ono %u\n", objsetno, sc, (unsigned int)*ono);

        /* *oxoff = *off % layout->fl_stripe_unit;  # offset in su */

Hi Gustavo,

This (and other u32/u64 issues in this function, is this the only
warning?) is fixed in my striping v2 work branch.  I wasn't going to
push that patch separately, but I guess I should post it.


Yeah, this was the only one warning reported by Coverity in this particular module.

Thanks
--
Gustavo





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