Messages in this thread | | | Date | Fri, 09 Feb 2018 11:36:40 -0600 | From | "Gustavo A. R. Silva" <> | Subject | Re: [PATCH] RDMA/nldev: Fix multiple potential NULL pointer dereferences |
| |
Quoting Leon Romanovsky <leon@kernel.org>:
> On Fri, Feb 09, 2018 at 09:56:00AM -0600, Gustavo A. R. Silva wrote: >> >> Quoting Leon Romanovsky <leon@kernel.org>: >> >> > On Fri, Feb 09, 2018 at 07:36:49AM -0600, Gustavo A. R. Silva wrote: >> > > Hi Leon, >> > > >> > > Quoting Leon Romanovsky <leon@kernel.org>: >> > > >> > > > On Fri, Feb 09, 2018 at 12:37:02AM -0600, Gustavo A. R. Silva wrote: >> > > > > In case the message header and payload cannot be stored, function >> > > > > nlmsg_put returns null. >> > > > > >> > > > > Fix this by adding multiple sanity checks and avoid a potential >> > > > > null dereference on _nlh_ when calling nlmsg_end. >> > > > > >> > > > > Addresses-Coverity-ID: 1454215 ("Dereference null return value") >> > > > > Addresses-Coverity-ID: 1454223 ("Dereference null return value") >> > > > > Addresses-Coverity-ID: 1454224 ("Dereference null return value") >> > > > > Addresses-Coverity-ID: 1464669 ("Dereference null return value") >> > > > > Addresses-Coverity-ID: 1464670 ("Dereference null return value") >> > > > > Addresses-Coverity-ID: 1464672 ("Dereference null return value") >> > > > > Fixes: e5c9469efcb1 ("RDMA/netlink: Add nldev device doit >> > > implementation") >> > > > > Fixes: c3f66f7b0052 ("RDMA/netlink: Implement nldev port >> doit callback") >> > > > > Fixes: 7d02f605f0dc ("RDMA/netlink: Add nldev port dumpit >> > > implementation") >> > > > > Fixes: b5fa635aab8f ("RDMA/nldev: Provide detailed QP information") >> > > > > Fixes: bf3c5a93c523 ("RDMA/nldev: Provide global resource >> utilization") >> > > > > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com> >> > > > > --- >> > > > > drivers/infiniband/core/nldev.c | 26 +++++++++++++++++++++++++- >> > > > > 1 file changed, 25 insertions(+), 1 deletion(-) >> > > > > >> > > > >> > > > It will be much better to fix the tool instead of fixing ghost case. >> > > > This scenario is impossible for all those flows. >> > > > We can receive the skv/msg in two ways: >> > > > * First by allocating new message with NLMSG_DEFAULT_SIZE, which has >> > > > more room >> > > > than nlmsg_total_size(payload), payload is 0. >> > > > * Second by getting from netlink.c and it will be at least "struct >> > > > nlmsghdr" too. >> > > > >> > > > Can you please add this info to the commit message? >> > > > >> > > >> > > Actually, I was planing to send a new version of this patch. >> This time using >> > > the unlikely macro for all the null checks on nlh. >> > > >> > > What do you think? >> > >> > It is not datapath, so "unlikely" is not needed. Let's assume that smart >> > enough >> > compiler will optimize such flow anyway, because nlmsg_put returns NULL >> > in unlikely scenario, so this check will be unlikely automatically too. >> > >> >> I'm curious about why the return value of nlmsg_put is null checked 118 out >> of 129 times (based on Coverity reports) in the last linux-next tree. >> >> So based on what you mention, do you think all those checks are actually >> unnecessary and, maybe they should be removed? > > I honestly don't know about all cases, but if message is allocated with > NLMSG_DEFAULT_SIZE and payload is 0, this check won't be needed. >
I got it.
> So go ahead, add check if (!...) in all places, but be cautious with > "potential null dereference" claims, it is not always true. >
You are right. I will update the subject and commit message.
Thanks for the feedback, Leon. I appreciate it. -- Gustavo
| |