systemd/0990-fd-util-rework-how-we-determine-highest-possible-fd.patch

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From 1b547e500207a469a533d819db5b7c6c22516ec3 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 17 Jan 2019 12:23:21 +0100
Subject: [PATCH] fd-util: rework how we determine highest possible fd
(cherry picked from commit 498e265df1c63212ec1a0991c135877a23f1ba4f)
Related: RHEL-18302
---
src/basic/fd-util.c | 37 ++++++++++++++++++++++++++-----------
1 file changed, 26 insertions(+), 11 deletions(-)
diff --git a/src/basic/fd-util.c b/src/basic/fd-util.c
index e085dc23b4..fea93d2039 100644
--- a/src/basic/fd-util.c
+++ b/src/basic/fd-util.c
@@ -188,6 +188,27 @@ _pure_ static bool fd_in_set(int fd, const int fdset[], size_t n_fdset) {
return false;
}
+static int get_max_fd(void) {
+ struct rlimit rl;
+ rlim_t m;
+
+ /* Return the highest possible fd, based RLIMIT_NOFILE, but enforcing FD_SETSIZE-1 as lower boundary
+ * and INT_MAX as upper boundary. */
+
+ if (getrlimit(RLIMIT_NOFILE, &rl) < 0)
+ return -errno;
+
+ m = MAX(rl.rlim_cur, rl.rlim_max);
+ if (m < FD_SETSIZE) /* Let's always cover at least 1024 fds */
+ return FD_SETSIZE-1;
+
+ if (m == RLIM_INFINITY || m > INT_MAX) /* Saturate on overflow. After all fds are "int", hence can
+ * never be above INT_MAX */
+ return INT_MAX;
+
+ return (int) (m - 1);
+}
+
int close_all_fds(const int except[], size_t n_except) {
_cleanup_closedir_ DIR *d = NULL;
struct dirent *de;
@@ -197,20 +218,14 @@ int close_all_fds(const int except[], size_t n_except) {
d = opendir("/proc/self/fd");
if (!d) {
- struct rlimit rl;
int fd, max_fd;
- /* When /proc isn't available (for example in chroots) the fallback is brute forcing through the fd
- * table */
-
- assert_se(getrlimit(RLIMIT_NOFILE, &rl) >= 0);
-
- if (rl.rlim_max == 0)
- return -EINVAL;
+ /* When /proc isn't available (for example in chroots) the fallback is brute forcing through
+ * the fd table */
- /* Let's take special care if the resource limit is set to unlimited, or actually larger than the range
- * of 'int'. Let's avoid implicit overflows. */
- max_fd = (rl.rlim_max == RLIM_INFINITY || rl.rlim_max > INT_MAX) ? INT_MAX : (int) (rl.rlim_max - 1);
+ max_fd = get_max_fd();
+ if (max_fd < 0)
+ return max_fd;
for (fd = 3; fd >= 0; fd = fd < max_fd ? fd + 1 : -1) {
int q;