From f60488f72e3c6839e3e77e4d35ceaad5367494b1 Mon Sep 17 00:00:00 2001
From: Daan De Meyer <daan.j.demeyer@gmail.com>
Date: Fri, 25 Aug 2023 13:55:36 +0200
Subject: [PATCH] Limit rlim_max in rlimit_nofile_safe() to nr_open

We might inherit a max rlim value that's larger than the kernel's
maximum (nr_open). This will cause setrlimit() to fail as the given
maximum is larger than the kernel's maximum. To get around this,
let's limit the max rlim we pass to rlimit() to the value of nr_open.

Should fix #28965

(cherry picked from commit f470dafddcd688c3ea6031d4bbcbf934fd094711)
(cherry picked from commit a980b83fe07521e4654d68331c31db3a4459412c)
(cherry picked from commit 30ce78cb1adff6a53bfaee57da4f208f35896dbe)

Conflict:NA
Reference:https://github.com/systemd/systemd-stable/commit/f60488f72e3c6839e3e77e4d35ceaad5367494b1
---
 src/basic/rlimit-util.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/basic/rlimit-util.c b/src/basic/rlimit-util.c
index 33dfde9d6c..e150976f75 100644
--- a/src/basic/rlimit-util.c
+++ b/src/basic/rlimit-util.c
@@ -401,7 +401,11 @@ int rlimit_nofile_safe(void) {
         if (rl.rlim_cur <= FD_SETSIZE)
                 return 0;
 
-        rl.rlim_cur = FD_SETSIZE;
+        /* So we might have inherited a hard limit that's larger than the kernel's maximum limit as stored in
+         * /proc/sys/fs/nr_open. If we pass this hard limit unmodified to setrlimit(), we'll get EPERM. To
+         * make sure that doesn't happen, let's limit our hard limit to the value from nr_open. */
+        rl.rlim_max = MIN(rl.rlim_max, (rlim_t) read_nr_open());
+        rl.rlim_cur = MIN((rlim_t) FD_SETSIZE, rl.rlim_max);
         if (setrlimit(RLIMIT_NOFILE, &rl) < 0)
                 return log_debug_errno(errno, "Failed to lower RLIMIT_NOFILE's soft limit to " RLIM_FMT ": %m", rl.rlim_cur);
 
-- 
2.33.0

