2019-05-26 09:27:36

by Bartosz Golaszewski

Subject: [kmod][PATCH] module: fix error path in kmod_module_probe_insert_module()

From: Bartosz Golaszewski <[email protected]>

The documentation says that kmod_module_probe_insert_module() will
return >0 if "stopped by a reason given in @flags" but it returns a
negative value if KMOD_PROBE_FAIL_ON_LOADED flag is passed and the
relevant module is already loaded. Fix the error path by using a
positive error value where required.

Signed-off-by: Bartosz Golaszewski <[email protected]>
---
libkmod/libkmod-module.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index bffe715..a3afaba 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -1253,7 +1253,7 @@ KMOD_EXPORT int kmod_module_probe_insert_module(struct kmod_module *mod,
if (!(flags & KMOD_PROBE_IGNORE_LOADED)
&& module_is_inkernel(mod)) {
if (flags & KMOD_PROBE_FAIL_ON_LOADED)
- return -EEXIST;
+ return EEXIST;
else
return 0;
}
@@ -1304,7 +1304,7 @@ KMOD_EXPORT int kmod_module_probe_insert_module(struct kmod_module *mod,
&& module_is_inkernel(m)) {
DBG(mod->ctx, "Ignoring module '%s': already loaded\n",
m->name);
- err = -EEXIST;
+ err = EEXIST;
goto finish_module;
}

@@ -1340,14 +1340,14 @@ finish_module:
* been loaded between the check and the moment we try to
* insert it.
*/
- if (err == -EEXIST && m == mod &&
+ if (err == EEXIST && m == mod &&
(flags & KMOD_PROBE_FAIL_ON_LOADED))
break;

/*
* Ignore errors from softdeps
*/
- if (err == -EEXIST || !m->required)
+ if (err == EEXIST || !m->required)
err = 0;

else if (err < 0)
--
2.21.0

2019-05-28 22:25:35

by Lucas De Marchi

Subject: Re: [kmod][PATCH] module: fix error path in kmod_module_probe_insert_module()

On Sun, May 26, 2019 at 11:25:12AM +0200, Bartosz Golaszewski wrote:
>From: Bartosz Golaszewski <[email protected]>
>
>The documentation says that kmod_module_probe_insert_module() will
>return >0 if "stopped by a reason given in @flags" but it returns a
>negative value if KMOD_PROBE_FAIL_ON_LOADED flag is passed and the
>relevant module is already loaded. Fix the error path by using a
>positive error value where required.
>
>Signed-off-by: Bartosz Golaszewski <[email protected]>
>---
> libkmod/libkmod-module.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
>diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
>index bffe715..a3afaba 100644
>--- a/libkmod/libkmod-module.c
>+++ b/libkmod/libkmod-module.c
>@@ -1253,7 +1253,7 @@ KMOD_EXPORT int kmod_module_probe_insert_module(struct kmod_module *mod,
> if (!(flags & KMOD_PROBE_IGNORE_LOADED)
> && module_is_inkernel(mod)) {
> if (flags & KMOD_PROBE_FAIL_ON_LOADED)
>- return -EEXIST;
>+ return EEXIST;
> else
> return 0;
> }
>@@ -1304,7 +1304,7 @@ KMOD_EXPORT int kmod_module_probe_insert_module(struct kmod_module *mod,
> && module_is_inkernel(m)) {
> DBG(mod->ctx, "Ignoring module '%s': already loaded\n",
> m->name);
>- err = -EEXIST;
>+ err = EEXIST;

this would break the ABI. modprobe for instance, that is in the same
repository would be broken by it:

kmod_list_foreach() {
...
if (err >= 0)
/* ignore flag return values such as a mod being blacklisted */
err = 0;
else {
switch (err) {
case -EEXIST:
...
}

I think we need to say the bug is actually in the bad documentation - my
bad actually, on commit b1a51256a9ed ("libkmod-module: probe: change
insertion to cover more use cases").

If you look at the definition of 'enum kmod_probe' you will see that
not all flags are returned as positive values - the only values that
have this behavior are the ones related to blacklist.

Could you rather patch the documentation?

thanks
Lucas De Marchi

> goto finish_module;
> }
>
>@@ -1340,14 +1340,14 @@ finish_module:
> * been loaded between the check and the moment we try to
> * insert it.
> */
>- if (err == -EEXIST && m == mod &&
>+ if (err == EEXIST && m == mod &&
> (flags & KMOD_PROBE_FAIL_ON_LOADED))
> break;
>
> /*
> * Ignore errors from softdeps
> */
>- if (err == -EEXIST || !m->required)
>+ if (err == EEXIST || !m->required)
> err = 0;
>
> else if (err < 0)
>--
>2.21.0
>