lkml.org 
[lkml]   [2018]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [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




\
 
 \ /
  Last update: 2018-02-09 18:37    [W:0.075 / U:1.848 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site