From 80efeebaf296dc4814e15d67977726b3ee93c048 Mon Sep 17 00:00:00 2001
From: Alejandro Colomar <alx@kernel.org>
Date: Fri, 31 May 2024 18:30:16 +0200
Subject: [PATCH] lib/idmapping.c: Use long constants in prctl(2), and remove
 0s

The prctl(2) system-call wrapper is implemented as a variadic function.
This makes it important to pass arguments to it of the right type (and
more importantly of the right width), to avoid undefined behavior.

While at it, check errors with ==-1, not <0, which is more explicit.

Also, PR_SET_KEEPCAPS(2const) doesn't need all arguments, so it can be
called with just two of them; remove unnecessary 0s.

See-also: prctl(2), PR_SET_KEEPCAPS(2const)
Link: <https://lore.kernel.org/linux-man/ddbdyaiptesjalgfmztxideej67e3yaob7ucsmbf6qvriwxiif@dohhxrqgwhrf/T/#med306b5b003f9cc7cc2de69fcdd7ee2d056d0954>
Cc: Xi Ruoyao <xry111@xry111.site>
Cc: Lukas Slebodnik <lslebodn@fedoraproject.org>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
---
 lib/idmapping.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/idmapping.c b/lib/idmapping.c
index fe3ccdfe3..5cbb6fefc 100644
--- a/lib/idmapping.c
+++ b/lib/idmapping.c
@@ -159,7 +159,7 @@ void write_mapping(int proc_dir_fd, int ranges, const struct map_range *mappings
 
 	/* Align setuid- and fscaps-based new{g,u}idmap behavior. */
 	if (geteuid() == 0 && geteuid() != ruid) {
-		if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) < 0) {
+		if (prctl(PR_SET_KEEPCAPS, 1L) == -1) {
 			fprintf(log_get_logfd(), _("%s: Could not prctl(PR_SET_KEEPCAPS)\n"), log_get_progname());
 			exit(EXIT_FAILURE);
 		}
