Messages in this thread | | | Date | Tue, 5 Dec 2017 20:56:07 +0300 | From | Serge Semin <> | Subject | Re: [PATCH v2 03/15] NTB: Fix UB/bug in ntb_mw_get_align() |
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On Tue, Dec 05, 2017 at 11:52:32AM -0500, Jon Mason <jdmason@kudzu.us> wrote: > On Sun, Dec 3, 2017 at 2:17 PM, Serge Semin <fancer.lancer@gmail.com> wrote: > > Simple (1 << pidx) operation causes undefined behaviour when > > pidx >= 32. It must be casted to u64 to match the actual return > > value of ntb_link_is_up() method, so to have all the possible > > peer indexes covered and to get rid of undefined behaviour. > > Additionally there are special macros in "linux/bitops.h" to perform > > the bit-set-shift operations, so it's recommended to have them used > > for proper bit setting. > > This looks good to me, but also seems like a bug fix. Please comment > on if this is not noticed. >
The consequences of the bug isn't noticeable at the moment, but potentially it can be seen on the devices like Switchtec (when multi-portness is finally added). Anyway it's better to fix it now, than to wait for obvious bug. Additionally as I said the originator of the code should have used BIT_ULL instead of the pure bit shifting.
Thanks, -Sergey
> Thanks, > Jon > > > > > Signed-off-by: Serge Semin <fancer.lancer@gmail.com> > > Reviewed-by: Logan Gunthorpe <logang@deltatee.com> > > --- > > include/linux/ntb.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/ntb.h b/include/linux/ntb.h > > index c1646f2c6344..488e586fb76c 100644 > > --- a/include/linux/ntb.h > > +++ b/include/linux/ntb.h > > @@ -764,7 +764,7 @@ static inline int ntb_mw_get_align(struct ntb_dev *ntb, int pidx, int widx, > > resource_size_t *size_align, > > resource_size_t *size_max) > > { > > - if (!(ntb_link_is_up(ntb, NULL, NULL) & (1 << pidx))) > > + if (!(ntb_link_is_up(ntb, NULL, NULL) & BIT_ULL(pidx))) > > return -ENOTCONN; > > > > return ntb->ops->mw_get_align(ntb, pidx, widx, addr_align, size_align, > > -- > > 2.12.0 > >
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