On Wed, 18 Apr 2012, Alex Elder wrote:
> On 12/14/2011 02:24 PM, Xi Wang wrote:
> > Given a large n, the bounds check (*p + n> end) can be bypassed due to
> > pointer wraparound. A safer check is (n> end - *p).
> >
> > Signed-off-by: Xi Wang<xi.wang@xxxxxxxxx>
>
> I noticed this proposed change never got committed.
>
> It looks good, but I don't like the name "ceph_need()".
>
> I am planning to pull this in soon, modified like this:
>
> static inline int ceph_need_ok(void **p, void *end, size_t n)
Would something like ceph_has_room() make more sense?
> {
> return end >= *p && n <= end - *p;
> }
>
> And then used like this:
>
> if (!likely(ceph_need_ok(p, end, n)))
>
> If you have an objection to that, please say so soon
> (and if you have no objection, please ACK).
>
> Reviewed-by: Alex Elder <elder@xxxxxxxxxxxxx>
>
> > ---
> > include/linux/ceph/decode.h | 9 +++++++--
> > 1 files changed, 7 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/ceph/decode.h b/include/linux/ceph/decode.h
> > index c5b6939..ea6db7b 100644
> > --- a/include/linux/ceph/decode.h
> > +++ b/include/linux/ceph/decode.h
> > @@ -12,6 +12,11 @@
> > * void *end pointer to end of buffer (last byte + 1)
> > */
> >
> > +static inline int ceph_need(void **p, void *end, size_t n)
> > +{
> > + return ((end< *p) || (n> end - *p));
> > +}
> > +
> > static inline u64 ceph_decode_64(void **p)
> > {
> > u64 v = get_unaligned_le64(*p);
> > @@ -47,7 +52,7 @@ static inline void ceph_decode_copy(void **p, void *pv,
> > size_t n)
> > */
> > #define ceph_decode_need(p, end, n, bad) \
> > do { \
> > - if (unlikely(*(p) + (n)> (end))) \
> > + if (unlikely(ceph_need(p, end, n))) \
> > goto bad; \
> > } while (0)
> >
> > @@ -166,7 +171,7 @@ static inline void ceph_encode_string(void **p, void
> > *end,
> >
> > #define ceph_encode_need(p, end, n, bad) \
> > do { \
> > - if (unlikely(*(p) + (n)> (end))) \
> > + if (unlikely(ceph_need(p, end, n))) \
> > goto bad; \
> > } while (0)
> >
>
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