The pstore infrastructure supports one single backend at a time;
trying to load a another backend causes an error and displays a
message, introduced on commit 0d7cd09a3dbb ("pstore: Improve
register_pstore() error reporting").

Happens that this message is not really clear about the situation,
also the current error returned (-EPERM) isn't accurate, whereas
-EBUSY makes more sense. We have another place in the code that
relies in the -EBUSY return for a similar check.

So, make it consistent here by returning -EBUSY and using a
similar message in both scenarios.

Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
---
 fs/pstore/platform.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 0c034ea39954..c32957e4b256 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -562,8 +562,9 @@ static int pstore_write_user_compat(struct pstore_record *record,
 int pstore_register(struct pstore_info *psi)
 {
 	if (backend && strcmp(backend, psi->name)) {
-		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
-		return -EPERM;
+		pr_warn("backend '%s' already in use: ignoring '%s'\n",
+			backend, psi->name);
+		return -EBUSY;
 	}
 
 	/* Sanity check flags. */
-- 
2.38.0

On Thu, Oct 06, 2022 at 07:42:05PM -0300, Guilherme G. Piccoli wrote:
> The pstore infrastructure supports one single backend at a time;
> trying to load a another backend causes an error and displays a
> message, introduced on commit 0d7cd09a3dbb ("pstore: Improve
> register_pstore() error reporting").
> 
> Happens that this message is not really clear about the situation,
> also the current error returned (-EPERM) isn't accurate, whereas
> -EBUSY makes more sense. We have another place in the code that
> relies in the -EBUSY return for a similar check.
> 
> So, make it consistent here by returning -EBUSY and using a
> similar message in both scenarios.
> 
> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
> ---
>  fs/pstore/platform.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
> index 0c034ea39954..c32957e4b256 100644
> --- a/fs/pstore/platform.c
> +++ b/fs/pstore/platform.c
> @@ -562,8 +562,9 @@ static int pstore_write_user_compat(struct pstore_record *record,
>  int pstore_register(struct pstore_info *psi)
>  {
>  	if (backend && strcmp(backend, psi->name)) {
> -		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
> -		return -EPERM;
> +		pr_warn("backend '%s' already in use: ignoring '%s'\n",
> +			backend, psi->name);
> +		return -EBUSY;

Thank you! Yes, this has bothered me for a while. :)

-- 
Kees Cook

On 06/10/2022 20:27, Kees Cook wrote:
> On Thu, Oct 06, 2022 at 07:42:05PM -0300, Guilherme G. Piccoli wrote:
>> The pstore infrastructure supports one single backend at a time;
>> trying to load a another backend causes an error and displays a
>> message, introduced on commit 0d7cd09a3dbb ("pstore: Improve
>> register_pstore() error reporting").
>>
>> Happens that this message is not really clear about the situation,
>> also the current error returned (-EPERM) isn't accurate, whereas
>> -EBUSY makes more sense. We have another place in the code that
>> relies in the -EBUSY return for a similar check.
>>
>> So, make it consistent here by returning -EBUSY and using a
>> similar message in both scenarios.
>>
>> Signed-off-by: Guilherme G. Piccoli <gpiccoli@igalia.com>
>> ---
>>  fs/pstore/platform.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
>> index 0c034ea39954..c32957e4b256 100644
>> --- a/fs/pstore/platform.c
>> +++ b/fs/pstore/platform.c
>> @@ -562,8 +562,9 @@ static int pstore_write_user_compat(struct pstore_record *record,
>>  int pstore_register(struct pstore_info *psi)
>>  {
>>  	if (backend && strcmp(backend, psi->name)) {
>> -		pr_warn("ignoring unexpected backend '%s'\n", psi->name);
>> -		return -EPERM;
>> +		pr_warn("backend '%s' already in use: ignoring '%s'\n",
>> +			backend, psi->name);
>> +		return -EBUSY;
> 
> Thank you! Yes, this has bothered me for a while. :)

Heheh ditto! Thank you for the great and fast review =)