Re: [dm-devel] dm: rename multipath path selector source files to have "dm-ps" prefix

[Mike Snitzer <snitzer@redhat.com>]

On Wed, Nov 11 2020 at  6:45am -0500,
Colin Ian King <colin.king@canonical.com> wrote:

> Hi,
> 
> Static analysis on linux-next has detected an initialized variable issue
> with the following recent commit:
> 
> commit 28784347451fdbf4671ba97018f816041ba2306a
> Author: Mike Snitzer <snitzer@redhat.com>
> Date:   Tue Nov 10 13:41:53 2020 -0500
> 
>     dm: rename multipath path selector source files to have "dm-ps" prefix
> 
> The analysis is as follows:
> 
>  43
> static int ioa_add_path(struct path_selector *ps, struct dm_path *path,
>  44                        int argc, char **argv, char **error)
>  45 {
>  46        struct selector *s = ps->context;
>  47        struct path_info *pi = NULL;
>    1. var_decl: Declaring variable cpu without initializer.
> 
>  48        unsigned int cpu;
>  49        int ret;
>  50
>    2. Condition argc != 1, taking false branch.
> 
>  51        if (argc != 1) {
>  52                *error = "io-affinity ps: invalid number of arguments";
>  53                return -EINVAL;
>  54        }
>  55
> 
>    Uninitialized scalar variable (UNINIT)
>    3. uninit_use_in_call: Using uninitialized value cpu when calling
> __cpu_to_node.
> 
>  56        pi = kzalloc_node(sizeof(*pi), GFP_KERNEL, cpu_to_node(cpu));
>  57        if (!pi) {
>  58                *error = "io-affinity ps: Error allocating path context";
>  59                return -ENOMEM;
>  60        }

Valid report, but it focuses on a follow-on commit that is just noise.
The commit "dm mpath: add IO affinity path selector" is what is in
quesation, see:
https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-5.11&id=c3d0a31e609e299836fa6ced28cb9ec06b408181

Regardless, Mike Christie, Colin's report has identified a bug.

Please advise on how you'd like to fix ioa_add_path()'s allocation of
'struct path_info'.. pretty sure 'cpu' will default to 0 (on stack)
despite no explicit initialization... so code "works" but does not
do so with a specific cpu allocation affinity.

Mike

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