Add log information in kernel-space when loading module failures.
Try to load the unsigned module and the module with bad signature
when set 1 to /sys/module/module/parameters/sig_enforce.

Unsigned module case:
(linux) insmod unsigned.ko
[   18.714661] Loading of unsigned module is rejected
insmod: can't insert 'unsigned.ko': Key was rejected by service
(linux)

Bad signature module case:
(linux) insmod bad_signature.ko
insmod: can't insert 'bad_signature.ko': Key was rejected by service
(linux)

There have different logging behavior the bad signature case only log
in user-space, add log info for fatal errors in module_sig_check().

Signed-off-by: Yusong Gao <a869920004@gmail.com>
---
V2: Change print level from notice to debug.
---
 kernel/module/signing.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/module/signing.c b/kernel/module/signing.c
index a2ff4242e623..b0c7b30e4d89 100644
--- a/kernel/module/signing.c
+++ b/kernel/module/signing.c
@@ -113,6 +113,7 @@ int module_sig_check(struct load_info *info, int flags)
 		 * unparseable signatures, and signature check failures --
 		 * even if signatures aren't required.
 		 */
+		pr_debug("Loading module failed (errno=%d)\n", -err);
 		return err;
 	}
 
-- 
2.34.1

On Wed, Jun 19, 2024 at 08:30:37AM +0000, Yusong Gao wrote:
> Add log information in kernel-space when loading module failures.
> Try to load the unsigned module and the module with bad signature
> when set 1 to /sys/module/module/parameters/sig_enforce.
> 
> Unsigned module case:
> (linux) insmod unsigned.ko
> [   18.714661] Loading of unsigned module is rejected
> insmod: can't insert 'unsigned.ko': Key was rejected by service
> (linux)
> 
> Bad signature module case:
> (linux) insmod bad_signature.ko
> insmod: can't insert 'bad_signature.ko': Key was rejected by service
> (linux)
> 
> There have different logging behavior the bad signature case only log
> in user-space, add log info for fatal errors in module_sig_check().
> 
> Signed-off-by: Yusong Gao <a869920004@gmail.com>
> ---
> V2: Change print level from notice to debug.
> ---
>  kernel/module/signing.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/module/signing.c b/kernel/module/signing.c
> index a2ff4242e623..b0c7b30e4d89 100644
> --- a/kernel/module/signing.c
> +++ b/kernel/module/signing.c
> @@ -113,6 +113,7 @@ int module_sig_check(struct load_info *info, int flags)
>  		 * unparseable signatures, and signature check failures --
>  		 * even if signatures aren't required.
>  		 */
> +		pr_debug("Loading module failed (errno=%d)\n", -err);

There are so many debug message, this doesn't help explain why, ie, tha
this is a signature issue.

  Luis