[PATCH 2/8] lib/path: add error handling to path_vcreate()

[Ruediger Meier <sweet_f_a@xxxxxx>]

From: Ruediger Meier <ruediger.meier@xxxxxxxxxxx>

Do not operate on truncated/random paths. Note, path_strdup()
can now really return NULL, to be handled in next commit.

Signed-off-by: Ruediger Meier <ruediger.meier@xxxxxxxxxxx>
---
 lib/path.c | 40 ++++++++++++++++++++++++++++++++--------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/lib/path.c b/lib/path.c
index eaa6d88..48ffe17 100644
--- a/lib/path.c
+++ b/lib/path.c
@@ -38,11 +38,21 @@ static char pathbuf[PATH_MAX];
 static const char *
 path_vcreate(const char *path, va_list ap)
 {
+	int rc;
+
 	if (prefixlen)
-		vsnprintf(pathbuf + prefixlen,
+		rc = vsnprintf(pathbuf + prefixlen,
 			  sizeof(pathbuf) - prefixlen, path, ap);
 	else
-		vsnprintf(pathbuf, sizeof(pathbuf), path, ap);
+		rc = vsnprintf(pathbuf, sizeof(pathbuf), path, ap);
+
+	if (rc < 0)
+		return NULL;
+	if ((size_t)rc >= sizeof(pathbuf)) {
+		errno = ENAMETOOLONG;
+		return NULL;
+	}
+
 	return pathbuf;
 }
 
@@ -64,11 +74,19 @@ path_vfopen(const char *mode, int exit_on_error, const char *path, va_list ap)
 {
 	FILE *f;
 	const char *p = path_vcreate(path, ap);
-
+	if (!p) {
+		p = "vpath";
+		goto err;
+	}
 	f = fopen(p, mode);
-	if (!f && exit_on_error)
-		err(EXIT_FAILURE, _("cannot open %s"), p);
+	if (!f)
+		goto err;
+
 	return f;
+err:
+	if (exit_on_error)
+		err(EXIT_FAILURE, _("cannot open %s"), p);
+	return NULL;
 }
 
 static int
@@ -76,11 +94,17 @@ path_vopen(int flags, const char *path, va_list ap)
 {
 	int fd;
 	const char *p = path_vcreate(path, ap);
-
+	if (!p) {
+		p = "vpath";
+		goto err;
+	}
 	fd = open(p, flags);
 	if (fd == -1)
-		err(EXIT_FAILURE, _("cannot open %s"), p);
+		goto err;
+
 	return fd;
+err:
+	err(EXIT_FAILURE, _("cannot open %s"), p);
 }
 
 FILE *
@@ -181,7 +205,7 @@ path_exist(const char *path, ...)
 	p = path_vcreate(path, ap);
 	va_end(ap);
 
-	return access(p, F_OK) == 0;
+	return p && access(p, F_OK) == 0;
 }
 
 #ifdef HAVE_CPU_SET_T
-- 
1.8.5.6

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