[LTP] [PATCH v2 0/2] Fix proc parsing in newuname01

[LTP] [PATCH v2 0/2] Fix proc parsing in newuname01

[Cyril Hrubis]

Turns out some of the strings in procfs can be empty (file with just a
newline) and in such case scanf("%s", ...) fails to read the file while
what we needed instead is a function that would produce an empty string.
This patchset addds such function and makes use of it in the
newuname01 test.

v2:
   - added returns to safe_file_read_str()
   - fixed typo in doc comment

Cyril Hrubis (2):
  lib: safe_file_ops: Add SAFE_FILE_READ_STR()
  syscalls: newuname01: Fix fail on empty domainname

 include/tst_safe_file_ops.h                   | 21 +++++++++++++++
 lib/safe_file_ops.c                           | 26 +++++++++++++++++++
 .../kernel/syscalls/newuname/newuname01.c     |  8 +++---
 3 files changed, 51 insertions(+), 4 deletions(-)

-- 
2.53.0


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[LTP] [PATCH v2 1/2] lib: safe_file_ops: Add SAFE_FILE_READ_STR()

[Cyril Hrubis]

Unlike the scanf("%s") this function can properly handle empty files and
in case of an empty file produces an empty string.

Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
---
 include/tst_safe_file_ops.h | 21 +++++++++++++++++++++
 lib/safe_file_ops.c         | 26 ++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/include/tst_safe_file_ops.h b/include/tst_safe_file_ops.h
index 0d8819594..73ebd2ab8 100644
--- a/include/tst_safe_file_ops.h
+++ b/include/tst_safe_file_ops.h
@@ -14,6 +14,27 @@
 	safe_file_scanf(__FILE__, __LINE__, NULL, \
 	                (path), (fmt), ## __VA_ARGS__)
 
+/**
+ * SAFE_FILE_READ_STR() - Reads a string from a file.
+ *
+ * Unlike scanf("%s") this function works fine with empty files or files that
+ * consist only of white spaces. In such case an empty string is stored into
+ * the supplied buffer.
+ *
+ * It's recommended to use this for various sysfs or procfs files that may be
+ * empty.
+ *
+ * @path: A path to a file.
+ * @buf: A buffer to store the string into.
+ * @buf_size: A buffer size.
+ */
+#define SAFE_FILE_READ_STR(path, buf, buf_size) \
+	safe_file_read_str(__FILE__, __LINE__, \
+	                   (path), (buf), (buf_size))
+
+void safe_file_read_str(const char *file, const int lineno,
+                        const char *path, char *buf, size_t buf_size);
+
 #define FILE_LINES_SCANF(path, fmt, ...) \
 	file_lines_scanf(__FILE__, __LINE__, NULL, 0,\
 			(path), (fmt), ## __VA_ARGS__)
diff --git a/lib/safe_file_ops.c b/lib/safe_file_ops.c
index 8314c4b1b..19da1fd97 100644
--- a/lib/safe_file_ops.c
+++ b/lib/safe_file_ops.c
@@ -160,6 +160,32 @@ void safe_file_scanf(const char *file, const int lineno,
 	}
 }
 
+void safe_file_read_str(const char *file, const int lineno,
+                        const char *path, char *buf, size_t buf_size)
+{
+	FILE *f;
+
+	f = fopen(path, "r");
+	if (!f) {
+		tst_brkm_(file, lineno, TBROK | TERRNO, NULL,
+		          "Failed to open FILE '%s' for reading", path);
+		return;
+	}
+
+	if (!fgets(buf, buf_size, f))
+		buf[0] = 0;
+
+	size_t len = strlen(buf);
+
+	if (len && buf[len-1] == '\n')
+		buf[len-1] = 0;
+
+	if (fclose(f)) {
+		tst_brkm_(file, lineno, TBROK | TERRNO, NULL,
+			"Failed to close FILE '%s'", path);
+		return;
+	}
+}
 
 /*
  * Try to parse each line from file specified by 'path' according
-- 
2.53.0


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[LTP] [PATCH v2 2/2] syscalls: newuname01: Fix fail on empty domainname

[Cyril Hrubis]

The domainname can be empty hence we cannot use scanf() string for
format for reading the file. Use the newly added SAFE_FILE_READ_STR()
to read the strings from procfs instead.

Fixes: https://github.com/linux-test-project/ltp/issues/1304
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
---
 testcases/kernel/syscalls/newuname/newuname01.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/testcases/kernel/syscalls/newuname/newuname01.c b/testcases/kernel/syscalls/newuname/newuname01.c
index 37058023a..995ea978e 100644
--- a/testcases/kernel/syscalls/newuname/newuname01.c
+++ b/testcases/kernel/syscalls/newuname/newuname01.c
@@ -31,16 +31,16 @@ static void run(void)
 
 	TST_EXP_EQ_STR(name->sysname, "Linux");
 
-	SAFE_FILE_SCANF("/proc/sys/kernel/hostname", "%1023[^\n]", proc_val);
+	SAFE_FILE_READ_STR("/proc/sys/kernel/hostname", proc_val, sizeof(proc_val));
 	TST_EXP_EQ_STR(name->nodename, proc_val);
 
-	SAFE_FILE_SCANF("/proc/sys/kernel/osrelease", "%1023[^\n]", proc_val);
+	SAFE_FILE_READ_STR("/proc/sys/kernel/osrelease", proc_val, sizeof(proc_val));
 	TST_EXP_EQ_STR(name->release, proc_val);
 
-	SAFE_FILE_SCANF("/proc/sys/kernel/version", "%1023[^\n]", proc_val);
+	SAFE_FILE_READ_STR("/proc/sys/kernel/version", proc_val, sizeof(proc_val));
 	TST_EXP_EQ_STR(name->version, proc_val);
 
-	SAFE_FILE_SCANF("/proc/sys/kernel/domainname", "%1023[^\n]", proc_val);
+	SAFE_FILE_READ_STR("/proc/sys/kernel/domainname", proc_val, sizeof(proc_val));
 	TST_EXP_EQ_STR(name->domainname, proc_val);
 }
 
-- 
2.53.0


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Re: [LTP] lib: safe_file_ops: Add SAFE_FILE_READ_STR()

[linuxtestproject.agent]

Hi Cyril,

--- [PATCH 1/2] ---

On Thu, 7 May 2026, Cyril Hrubis wrote:
> lib: safe_file_ops: Add SAFE_FILE_READ_STR()

> +	if (!fgets(buf, buf_size, f))
> +		buf[0] = 0;
> +
> +	size_t len = strlen(buf);

Move `size_t len` to the top of the function alongside `FILE *f`; mixed
declarations after executable statements violate kernel coding style.

--- [PATCH 2/2] ---

On Thu, 7 May 2026, Cyril Hrubis wrote:
> syscalls: newuname01: Fix fail on empty domainname

> Fixes: https://github.com/linux-test-project/ltp/issues/1304

`Fixes:` must reference a git commit hash in the form
`Fixes: <hash> ("<subject>")`. Use `Closes:` to reference GitHub issues.

---
Note:

Our agent completed the review of the patch.

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Re: [LTP] lib: safe_file_ops: Add SAFE_FILE_READ_STR()

[Andrea Cervesato via ltp]

Hi,

> Hi Cyril,
> 
> --- [PATCH 1/2] ---
> 
> On Thu, 7 May 2026, Cyril Hrubis wrote:
> > lib: safe_file_ops: Add SAFE_FILE_READ_STR()
> 
> > +	if (!fgets(buf, buf_size, f))
> > +		buf[0] = 0;
> > +
> > +	size_t len = strlen(buf);
> 
> Move `size_t len` to the top of the function alongside `FILE *f`; mixed
> declarations after executable statements violate kernel coding style.

I see this is happening again. I'm gonna add a rule for it.

> 
> --- [PATCH 2/2] ---
> 
> On Thu, 7 May 2026, Cyril Hrubis wrote:
> > syscalls: newuname01: Fix fail on empty domainname
> 
> > Fixes: https://github.com/linux-test-project/ltp/issues/1304
> 
> `Fixes:` must reference a git commit hash in the form
> `Fixes: <hash> ("<subject>")`. Use `Closes:` to reference GitHub issues.
> 

This is actually correct. I will change the Fixes to Closes
before merge.

Regards,
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SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com

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Re: [LTP] [PATCH v2 1/2] lib: safe_file_ops: Add SAFE_FILE_READ_STR()

[Andrea Cervesato via ltp]

Reviewed-by: Andrea Cervesato <andrea.cervesato@suse.com>

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Re: [LTP] [PATCH v2 2/2] syscalls: newuname01: Fix fail on empty domainname

[Andrea Cervesato via ltp]

Reviewed-by: Andrea Cervesato <andrea.cervesato@suse.com>

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Re: [LTP] [PATCH v2 0/2] Fix proc parsing in newuname01

[Andrea Cervesato via ltp]

Merged, Thanks!

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