sysusers: make sure to reset the returned value when EOF is reached in fget*ent_sane() wrappers (#8737)

To indicate that the there're no more entries, these wrappers return false but
did leave the passed pointed unmodified.

However EOF is not an error and is a very common case so initialize the output
argument to NULL even in this case so callers don't need to do that.

Fixes: #8721

6 files changed, 15 insertions, 20 deletions

diff --git a/src/basic/user-util.c b/src/basic/user-util.c
index 1effd55b0..0f0f21dbc 100644
--- a/src/basic/user-util.c
+++ b/src/basic/user-util.c
@@ -775,14 +775,11 @@ int fgetpwent_sane(FILE *stream, struct passwd **pw) {
 
         errno = 0;
         p = fgetpwent(stream);
-        if (p == NULL) {
-                if (errno == ENOENT)
-                        return false;
+        if (p == NULL && errno != ENOENT)
                 return errno > 0 ? -errno : -EIO;
-        }
 
         *pw = p;
-        return true;
+        return p != NULL;
 }
 
 int fgetspent_sane(FILE *stream, struct spwd **sp) {
@@ -793,14 +790,11 @@ int fgetspent_sane(FILE *stream, struct spwd **sp) {
 
         errno = 0;
         s = fgetspent(stream);
-        if (s == NULL) {
-                if (errno == ENOENT)
-                        return false;
+        if (s == NULL && errno != ENOENT)
                 return errno > 0 ? -errno : -EIO;
-        }
 
         *sp = s;
-        return true;
+        return s != NULL;
 }
 
 int fgetgrent_sane(FILE *stream, struct group **gr) {
@@ -811,14 +805,11 @@ int fgetgrent_sane(FILE *stream, struct group **gr) {
 
         errno = 0;
         g = fgetgrent(stream);
-        if (g == NULL) {
-                if (errno == ENOENT)
-                        return false;
+        if (g == NULL && errno != ENOENT)
                 return errno > 0 ? -errno : -EIO;
-        }
 
         *gr = g;
-        return true;
+        return g != NULL;
 }
 
 #if ENABLE_GSHADOW
@@ -830,13 +821,10 @@ int fgetsgent_sane(FILE *stream, struct sgrp **sg) {
 
         errno = 0;
         s = fgetsgent(stream);
-        if (s == NULL) {
-                if (errno == ENOENT)
-                        return false;
+        if (s == NULL && errno != ENOENT)
                 return errno > 0 ? -errno : -EIO;
-        }
 
         *sg = s;
-        return true;
+        return s != NULL;
 }
 #endif
diff --git a/test/TEST-21-SYSUSERS/test-12.expected-group b/test/TEST-21-SYSUSERS/test-12.expected-group
new file mode 100644
index 000000000..5d94846ed
--- /dev/null
+++ b/test/TEST-21-SYSUSERS/test-12.expected-group
@@ -0,0 +1,2 @@
+root:x:0:
+systemd-coredump:x:1:
diff --git a/test/TEST-21-SYSUSERS/test-12.expected-passwd b/test/TEST-21-SYSUSERS/test-12.expected-passwd
new file mode 100644
index 000000000..75fe9b420
--- /dev/null
+++ b/test/TEST-21-SYSUSERS/test-12.expected-passwd
@@ -0,0 +1,2 @@
+root:x:0:0:root:/root:/bin/bash
+systemd-coredump:x:1:1:systemd Core Dumper:/:/sbin/nologin
diff --git a/test/TEST-21-SYSUSERS/test-12.initial-group b/test/TEST-21-SYSUSERS/test-12.initial-group
new file mode 100644
index 000000000..1dbf9013e
--- /dev/null
+++ b/test/TEST-21-SYSUSERS/test-12.initial-group
@@ -0,0 +1 @@
+root:x:0:
diff --git a/test/TEST-21-SYSUSERS/test-12.initial-passwd b/test/TEST-21-SYSUSERS/test-12.initial-passwd
new file mode 100644
index 000000000..aebc4923f
--- /dev/null
+++ b/test/TEST-21-SYSUSERS/test-12.initial-passwd
@@ -0,0 +1 @@
+root:x:0:0:root:/root:/bin/bash
diff --git a/test/TEST-21-SYSUSERS/test-12.input b/test/TEST-21-SYSUSERS/test-12.input
new file mode 100644
index 000000000..291312027
--- /dev/null
+++ b/test/TEST-21-SYSUSERS/test-12.input
@@ -0,0 +1 @@
+u systemd-coredump  1 "systemd Core Dumper"