user-util: add get{pw,gr}{uid,gid,name}_malloc() helpers

These are wrappers around getpwuid_r() and friends, and will allocate the
right-sized buffer for this call.

We so far had multiple implementations of a buffer allocation loop
around getpwuid_r() and friends, and they all suck in some way. Let's
clean this up and add a common implementation, and use it everywhere.

Also, be more careful with error numbers, in particular systematically
turn ENOENT into ENOSRCH (the former is what is returned if /etc/passwd
is absent, which we want to consider identical to user not existing,
which is ENOSRCH). We so far did this at some invocations, but not all.

There are some invocations of getpwuid() left in the codebase. We really
should fix those too, and have a single unified implementation of the
logic, but those are not as trivial to convert, so left for another
time.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/nspawn/nspawn.c b/src/nspawn/nspawn.c
index c48b51323b..89ef0e4daa 100644
--- a/src/nspawn/nspawn.c
+++ b/src/nspawn/nspawn.c
@@ -4211,13 +4211,13 @@ static int uid_shift_pick(uid_t *shift, LockFile *ret_lock_file) {
                         return r;
 
                 /* Make some superficial checks whether the range is currently known in the user database */
-                if (getpwuid(candidate))
+                if (getpwuid_malloc(candidate, /* ret= */ NULL) >= 0)
                         goto next;
-                if (getpwuid(candidate + UINT32_C(0xFFFE)))
+                if (getpwuid_malloc(candidate + UINT32_C(0xFFFE), /* ret= */ NULL) >= 0)
                         goto next;
-                if (getgrgid(candidate))
+                if (getgrgid_malloc(candidate, /* ret= */ NULL) >= 0)
                         goto next;
-                if (getgrgid(candidate + UINT32_C(0xFFFE)))
+                if (getgrgid_malloc(candidate + UINT32_C(0xFFFE), /* ret= */ NULL) >= 0)
                         goto next;
 
                 *ret_lock_file = lf;