[LTP] [PATCH] lib: Handle empty saved configuration values

[LTP] [PATCH] lib: Handle empty saved configuration values

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

Empty string module parameters return EOF on older kernels, causing
fw_load02 to abort with TBROK on v4.4.

Accept empty values while retaining read-error handling and the original
errno. Restore empty strings with a NUL byte: an empty write does not
invoke the sysfs setter, while a newline would change the saved value.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
Fix the following behaviour on kernel < 4.14 96802e6b1dbf

tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
tst_security.c:115: TINFO: SecureBoot sysfs file not available
tst_security.c:94: TINFO: Unable to determine system lockdown state
tst_security.c:115: TINFO: SecureBoot sysfs file not available
tst_tmpdir.c:309: TINFO: Using /tmp/LTP_fw_ZRzLML as tmpdir (btrfs filesystem)
tst_sys_conf.c:103: TBROK: Failed to read anything from '/sys/module/firmware_class/parameters/path': SUCCESS (0)

Summary:
passed   0
failed   0
broken   1
skipped  0
warnings 0
---
 lib/tst_sys_conf.c | 27 ++++++++++++++++++++++-----
 1 file changed, 22 insertions(+), 5 deletions(-)

diff --git a/lib/tst_sys_conf.c b/lib/tst_sys_conf.c
index 80cd83569..a62af4a94 100644
--- a/lib/tst_sys_conf.c
+++ b/lib/tst_sys_conf.c
@@ -56,6 +56,7 @@ int tst_sys_conf_save(const struct tst_path_val *conf)
 {
 	char line[PATH_MAX];
 	int ttype, iret;
+	int read_err, saved_errno;
 	FILE *fp;
 	void *ret;
 
@@ -93,14 +94,23 @@ int tst_sys_conf_save(const struct tst_path_val *conf)
 	}
 
 	ret = fgets(line, sizeof(line), fp);
+	saved_errno = errno;
+	read_err = ferror(fp);
+
 	fclose(fp);
 
 	if (ret == NULL) {
-		if (conf->flags & TST_SR_IGNORE_ERR)
-			return 1;
+		if (read_err) {
+			if (conf->flags & TST_SR_IGNORE_ERR)
+				return 1;
+
+			errno = saved_errno;
+			tst_brk(TBROK | TERRNO, "Failed to read anything from '%s'",
+				conf->path);
+		}
 
-		tst_brk(TBROK | TERRNO, "Failed to read anything from '%s'",
-			conf->path);
+		/* Empty string module parameters can return EOF on older kernels. */
+		line[0] = '\0';
 	}
 
 	tst_sys_conf_save_str(conf->path, line);
@@ -142,7 +152,14 @@ void tst_sys_conf_restore(int verbose)
 			tst_res(TINFO, "Restoring conf.: %s -> %s\n",
 				i->path, i->value);
 		}
-		FILE_PRINTF(i->path, "%s", i->value);
+		/*
+		 * A zero-length write does not invoke the sysfs store callback.
+		 * Write a NUL byte to restore an empty string module parameter.
+		 */
+		if (!i->value[0])
+			FILE_PRINTF(i->path, "%c", '\0');
+		else
+			FILE_PRINTF(i->path, "%s", i->value);
 	}
 }
 

---
base-commit: 0596b09f22f449cb300e8ad2d08d8b186f551a05
change-id: 20260929-fix_fw_load02-6b0305f6bd7b

Best regards,
--  
Andrea Cervesato <andrea.cervesato@suse.com>


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Re: [LTP] [PATCH] lib: Handle empty saved configuration values

[Cyril Hrubis]

Hi!
Reviewed-by: Cyril Hrubis <chrubis@suse.cz>

-- 
Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] [PATCH] lib: Handle empty saved configuration values

[Petr Vorel]

Hi Andrea,

> Empty string module parameters return EOF on older kernels, causing
> fw_load02 to abort with TBROK on v4.4.

> Accept empty values while retaining read-error handling and the original
> errno. Restore empty strings with a NUL byte: an empty write does not
> invoke the sysfs setter, while a newline would change the saved value.

Thanks for the fix, LGTM.

Reviewed-by: Petr Vorel <pvorel@suse.cz>

> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
> Fix the following behaviour on kernel < 4.14 96802e6b1dbf

Could you please put kernel version and git hash to the commit message?

Kind regards,
Petr

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Re: [LTP] [PATCH] lib: Handle empty saved configuration values

[Martin Doucha]

Hi,
one suggestion below.

On 9/29/26 16:15, Andrea Cervesato wrote:
> From: Andrea Cervesato <andrea.cervesato@suse.com>
> 
> Empty string module parameters return EOF on older kernels, causing
> fw_load02 to abort with TBROK on v4.4.
> 
> Accept empty values while retaining read-error handling and the original
> errno. Restore empty strings with a NUL byte: an empty write does not
> invoke the sysfs setter, while a newline would change the saved value.
> 
> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
> Fix the following behaviour on kernel < 4.14 96802e6b1dbf
> 
> tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
> tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
> tst_kconfig.c:90: TINFO: Parsing kernel config '/proc/config.gz'
> tst_security.c:115: TINFO: SecureBoot sysfs file not available
> tst_security.c:94: TINFO: Unable to determine system lockdown state
> tst_security.c:115: TINFO: SecureBoot sysfs file not available
> tst_tmpdir.c:309: TINFO: Using /tmp/LTP_fw_ZRzLML as tmpdir (btrfs filesystem)
> tst_sys_conf.c:103: TBROK: Failed to read anything from '/sys/module/firmware_class/parameters/path': SUCCESS (0)
> 
> Summary:
> passed   0
> failed   0
> broken   1
> skipped  0
> warnings 0
> ---
>   lib/tst_sys_conf.c | 27 ++++++++++++++++++++++-----
>   1 file changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/lib/tst_sys_conf.c b/lib/tst_sys_conf.c
> index 80cd83569..a62af4a94 100644
> --- a/lib/tst_sys_conf.c
> +++ b/lib/tst_sys_conf.c
> @@ -56,6 +56,7 @@ int tst_sys_conf_save(const struct tst_path_val *conf)
>   {
>   	char line[PATH_MAX];
>   	int ttype, iret;
> +	int read_err, saved_errno;
>   	FILE *fp;
>   	void *ret;
>   
> @@ -93,14 +94,23 @@ int tst_sys_conf_save(const struct tst_path_val *conf)
>   	}
>   
>   	ret = fgets(line, sizeof(line), fp);
> +	saved_errno = errno;
> +	read_err = ferror(fp);
> +
>   	fclose(fp);
>   
>   	if (ret == NULL) {
> -		if (conf->flags & TST_SR_IGNORE_ERR)
> -			return 1;
> +		if (read_err) {
> +			if (conf->flags & TST_SR_IGNORE_ERR)
> +				return 1;
> +
> +			errno = saved_errno;
> +			tst_brk(TBROK | TERRNO, "Failed to read anything from '%s'",
> +				conf->path);
> +		}
>   
> -		tst_brk(TBROK | TERRNO, "Failed to read anything from '%s'",
> -			conf->path);
> +		/* Empty string module parameters can return EOF on older kernels. */
> +		line[0] = '\0';
>   	}
>   

I think you can drop most of this chunk and do two things instead:
1) char line[PATH_MAX] = {};
2) if (ret == NULL) -> if (read_err).

-- 
Martin Doucha   mdoucha@suse.cz
SW Quality Engineer
SUSE LINUX, s.r.o.
CORSO IIa
Krizikova 148/34
186 00 Prague 8
Czech Republic

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Re: [LTP] lib: Handle empty saved configuration values

[linuxtestproject.agent]

Hi Andrea,

On Tue Sep 29 16:15:19 2026 +0200, Andrea Cervesato wrote:
> lib: Handle empty saved configuration values

Verdict - Reviewed

---
Note:

The agent can sometimes produce false positives although often its
findings are genuine. If you find issues with the review, please
comment this email or ignore the suggestions.

Regards,
LTP AI Reviewer

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