[PATCH] libkmod-module: convert return value from system() to errno

[PATCH] libkmod-module: convert return value from system() to errno

[Topi Miettinen]

[-- Attachment #1: Type: text/plain, Size: 1069 bytes --]

Don't use exit status of a command directly as errno code, callers
will be confused.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
---
  libkmod/libkmod-module.c | 8 +++++---
  1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 8044a8f..6031d80 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod, 
const char *type,
         if (err == -1 || WEXITSTATUS(err)) {
                 ERR(mod->ctx, "Error running %s command for %s\n",
                                                                 type, 
modname);
-               if (err != -1)
-                       err = -WEXITSTATUS(err);
+               if (err != -1) /* nonzero exit status: something bad 
happened */
+                       return -EINVAL;
+               else /* child process could not be created */
+                       return -errno;
         }

-       return err;
+       return 0;
  }

  struct probe_insert_cb {
-- 
2.24.0

[-- Attachment #2: 0001-libkmod-module-convert-return-value-from-system-to-e.patch --]
[-- Type: text/x-diff, Size: 1099 bytes --]

From f560864a4a8fd61c2881cfefb970db27c2418690 Mon Sep 17 00:00:00 2001
From: Topi Miettinen <toiwoton@gmail.com>
Date: Mon, 23 Dec 2019 18:58:13 +0200
Subject: [PATCH] libkmod-module: convert return value from system() to errno

Don't use exit status of a command directly as errno code, callers
will be confused.

Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
---
 libkmod/libkmod-module.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 8044a8f..6031d80 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod, const char *type,
 	if (err == -1 || WEXITSTATUS(err)) {
 		ERR(mod->ctx, "Error running %s command for %s\n",
 								type, modname);
-		if (err != -1)
-			err = -WEXITSTATUS(err);
+		if (err != -1) /* nonzero exit status: something bad happened */
+			return -EINVAL;
+		else /* child process could not be created */
+			return -errno;
 	}
 
-	return err;
+	return 0;
 }
 
 struct probe_insert_cb {
-- 
2.24.0

Re: [PATCH] libkmod-module: convert return value from system() to errno

[Lucas De Marchi]

On Mon, Dec 23, 2019 at 9:07 AM Topi Miettinen <toiwoton@gmail.com> wrote:
>
> Don't use exit status of a command directly as errno code, callers
> will be confused.
>
> Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
> ---
>   libkmod/libkmod-module.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 8044a8f..6031d80 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod,
> const char *type,
>          if (err == -1 || WEXITSTATUS(err)) {
>                  ERR(mod->ctx, "Error running %s command for %s\n",
>                                                                  type,
> modname);
> -               if (err != -1)
> -                       err = -WEXITSTATUS(err);

I don't think we actually care about differentiating them. So just a plain
return -EINVAL;  here would suffice, makes sense?

Lucas De Marchi

> +               if (err != -1) /* nonzero exit status: something bad
> happened */
> +                       return -EINVAL;
> +               else /* child process could not be created */
> +                       return -errno;
>          }
>
> -       return err;
> +       return 0;
>   }
>
>   struct probe_insert_cb {
> --
> 2.24.0



-- 
Lucas De Marchi

Re: [PATCH] libkmod-module: convert return value from system() to errno

[Topi Miettinen]

On 24.12.2019 4.54, Lucas De Marchi wrote:
> On Mon, Dec 23, 2019 at 9:07 AM Topi Miettinen <toiwoton@gmail.com> wrote:
>>
>> Don't use exit status of a command directly as errno code, callers
>> will be confused.
>>
>> Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
>> ---
>>    libkmod/libkmod-module.c | 8 +++++---
>>    1 file changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
>> index 8044a8f..6031d80 100644
>> --- a/libkmod/libkmod-module.c
>> +++ b/libkmod/libkmod-module.c
>> @@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod,
>> const char *type,
>>           if (err == -1 || WEXITSTATUS(err)) {
>>                   ERR(mod->ctx, "Error running %s command for %s\n",
>>                                                                   type,
>> modname);
>> -               if (err != -1)
>> -                       err = -WEXITSTATUS(err);
> 
> I don't think we actually care about differentiating them. So just a plain
> return -EINVAL;  here would suffice, makes sense?

I think it would lose potentially valuable information. For example 
EPERM could tell the system administrator of a problem with MAC 
configuration preventing execution of the shell, ENOENT could show that 
the shell or shared libraries are missing and so forth.

-Topi

Re: [PATCH] libkmod-module: convert return value from system() to errno

[Lucas De Marchi]

On Tue, Dec 24, 2019 at 11:54:58AM +0200, Topi Miettinen wrote:
>On 24.12.2019 4.54, Lucas De Marchi wrote:
>>On Mon, Dec 23, 2019 at 9:07 AM Topi Miettinen <toiwoton@gmail.com> wrote:
>>>
>>>Don't use exit status of a command directly as errno code, callers
>>>will be confused.
>>>
>>>Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
>>>---
>>>   libkmod/libkmod-module.c | 8 +++++---
>>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>>diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
>>>index 8044a8f..6031d80 100644
>>>--- a/libkmod/libkmod-module.c
>>>+++ b/libkmod/libkmod-module.c
>>>@@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod,
>>>const char *type,
>>>          if (err == -1 || WEXITSTATUS(err)) {
>>>                  ERR(mod->ctx, "Error running %s command for %s\n",
>>>                                                                  type,
>>>modname);
>>>-               if (err != -1)
>>>-                       err = -WEXITSTATUS(err);
>>
>>I don't think we actually care about differentiating them. So just a plain
>>return -EINVAL;  here would suffice, makes sense?
>
>I think it would lose potentially valuable information. For example 
>EPERM could tell the system administrator of a problem with MAC 
>configuration preventing execution of the shell, ENOENT could show 
>that the shell or shared libraries are missing and so forth.

makes sense, but we take decisions on the callers depending on the
return value. I don't want to mix that with return values from the
commands executed. E.g. if the command returned EEXIST the caller would
treat a fail differently.

I think it would be good here to give different error messages and
always return -EINVAL. I'm thinking on squashing the following diff,
what do you think?


diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 6031d80..714ee21 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -980,13 +980,16 @@ static int command_do(struct kmod_module *mod, const char *type,
  	err = system(cmd);
  	unsetenv("MODPROBE_MODULE");
  
-	if (err == -1 || WEXITSTATUS(err)) {
-		ERR(mod->ctx, "Error running %s command for %s\n",
-								type, modname);
-		if (err != -1) /* nonzero exit status: something bad happened */
-			return -EINVAL;
-		else /* child process could not be created */
-			return -errno;
+	if (err == -1) {
+		ERR(mod->ctx, "Could not run %s command '%s' for module %s: %m\n",
+		    type, cmd, modname);
+		return -EINVAL;
+	}
+
+	if (WEXITSTATUS(err)) {
+		ERR(mod->ctx, "Error running %s command '%s' for module %s: retcode %d\n",
+		    type, cmd, modname, WEXITSTATUS(err));
+		return -EINVAL;
  	}
  
  	return 0;


thanks
Lucas De Marchi

Re: [PATCH] libkmod-module: convert return value from system() to errno

[Topi Miettinen]

On 29.12.2019 0.59, Lucas De Marchi wrote:
> On Tue, Dec 24, 2019 at 11:54:58AM +0200, Topi Miettinen wrote:
>> On 24.12.2019 4.54, Lucas De Marchi wrote:
>>> On Mon, Dec 23, 2019 at 9:07 AM Topi Miettinen <toiwoton@gmail.com> 
>>> wrote:
>>>>
>>>> Don't use exit status of a command directly as errno code, callers
>>>> will be confused.
>>>>
>>>> Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
>>>> ---
>>>>   libkmod/libkmod-module.c | 8 +++++---
>>>>   1 file changed, 5 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
>>>> index 8044a8f..6031d80 100644
>>>> --- a/libkmod/libkmod-module.c
>>>> +++ b/libkmod/libkmod-module.c
>>>> @@ -983,11 +983,13 @@ static int command_do(struct kmod_module *mod,
>>>> const char *type,
>>>>          if (err == -1 || WEXITSTATUS(err)) {
>>>>                  ERR(mod->ctx, "Error running %s command for %s\n",
>>>>                                                                  type,
>>>> modname);
>>>> -               if (err != -1)
>>>> -                       err = -WEXITSTATUS(err);
>>>
>>> I don't think we actually care about differentiating them. So just a 
>>> plain
>>> return -EINVAL;  here would suffice, makes sense?
>>
>> I think it would lose potentially valuable information. For example 
>> EPERM could tell the system administrator of a problem with MAC 
>> configuration preventing execution of the shell, ENOENT could show 
>> that the shell or shared libraries are missing and so forth.
> 
> makes sense, but we take decisions on the callers depending on the
> return value. I don't want to mix that with return values from the
> commands executed. E.g. if the command returned EEXIST the caller would
> treat a fail differently.
> 
> I think it would be good here to give different error messages and
> always return -EINVAL. I'm thinking on squashing the following diff,
> what do you think?

OK, maybe that's better.

-Topi

> 
> diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
> index 6031d80..714ee21 100644
> --- a/libkmod/libkmod-module.c
> +++ b/libkmod/libkmod-module.c
> @@ -980,13 +980,16 @@ static int command_do(struct kmod_module *mod, 
> const char *type,
>       err = system(cmd);
>       unsetenv("MODPROBE_MODULE");
> 
> -    if (err == -1 || WEXITSTATUS(err)) {
> -        ERR(mod->ctx, "Error running %s command for %s\n",
> -                                type, modname);
> -        if (err != -1) /* nonzero exit status: something bad happened */
> -            return -EINVAL;
> -        else /* child process could not be created */
> -            return -errno;
> +    if (err == -1) {
> +        ERR(mod->ctx, "Could not run %s command '%s' for module %s: %m\n",
> +            type, cmd, modname);
> +        return -EINVAL;
> +    }
> +
> +    if (WEXITSTATUS(err)) {
> +        ERR(mod->ctx, "Error running %s command '%s' for module %s: 
> retcode %d\n",
> +            type, cmd, modname, WEXITSTATUS(err));
> +        return -EINVAL;
>       }
> 
>       return 0;
> 
> 
> thanks
> Lucas De Marchi