Re: [PATCH rdma-core] verbs: Do not copy uninitialized data in ibv_cmd_modify_qp

[Bart Van Assche <Bart.VanAssche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>]

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On Thu, 2016-12-22 at 15:13 -0700, Jason Gunthorpe wrote:
> Valgrind reports:
> 
> ==1196== Syscall param write(buf) points to uninitialised byte(s)
> ==1196==    at 0x506250D: ??? (syscall-template.S:84)
> ==1196==    by 0x527756F: ibv_cmd_modify_qp (cmd.c:1291)
> ==1196==    by 0x8008D74: mlx4_modify_qp (verbs.c:820)
> ==1196==    by 0x527E4F4: ibv_modify_qp@@IBVERBS_1.1 (verbs.c:561)
> ==1196==    by 0x4E3FAB3: ucma_modify_qp_err.isra.6 (cma.c:1115)
> ==1196==    by 0x4E41D56: rdma_get_cm_event.part.15 (cma.c:2180)
> ==1196==    by 0x402CF0: cm_thread (rping.c:576)
> ==1196==    by 0x5059709: start_thread (pthread_create.c:333)
> ==1196==    by 0x558A82C: clone (clone.S:109)
> ==1196==  Address 0x9847980 is on thread 2's stack
> ==1196==  in frame #2, created by mlx4_modify_qp (verbs.c:775)
> 
> This is because of code like this:
> 
>         struct ibv_qp_attr qp_attr;
>         qp_attr.qp_state = IBV_QPS_ERR;
>         return rdma_seterrno(ibv_modify_qp(id->qp, &qp_attr, IBV_QP_STATE));
> 
> Always pass 0 into the kernel for for attributes that are not requested
> to be modified.

Hello Jason,

Have you considered to modify Valgrind? It is possible to modify Valgrind
such that it doesn't report false positives like the above report without
changing the rdma-core code. See also PRE(sys_ioctl) in source file
coregrind/m_syswrap/syswrap-linux.c.

Bart.
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