From c9c6537731d21c00ef5829003db0bb694c6aec56 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=D0=BD=D0=B0=D0=B1?= <nabijaczleweli@nabijaczleweli.xyz>
Date: Sat, 3 Apr 2021 12:09:24 +0200
Subject: [PATCH] zed: only go up to current limit in close_from() fallback
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Consider the following strace log:
  prlimit64(0, RLIMIT_NOFILE,
            NULL, {rlim_cur=1024, rlim_max=1024*1024}) = 0
  dup2(0, 30)                         = 30
  dup2(0, 300)                        = 300
  dup2(0, 3000)                       = -1 EBADF (Bad file descriptor)
  dup2(0, 30000)                      = -1 EBADF (Bad file descriptor)
  dup2(0, 300000)                     = -1 EBADF (Bad file descriptor)
  prlimit64(0, RLIMIT_NOFILE,
            {rlim_cur=1024*1024, rlim_max=1024*1024}, NULL) = 0
  dup2(0, 30)                         = 30
  dup2(0, 300)                        = 300
  dup2(0, 3000)                       = 3000
  dup2(0, 30000)                      = 30000
  dup2(0, 300000)                     = 300000

Even a privileged process needs to bump its rlimit before being able
to use fds higher than rlim_cur.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Closes #11834
---
 cmd/zed/zed_file.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/cmd/zed/zed_file.c b/cmd/zed/zed_file.c
index 401ab89eb..0e7086d9e 100644
--- a/cmd/zed/zed_file.c
+++ b/cmd/zed/zed_file.c
@@ -17,7 +17,6 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <string.h>
-#include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <unistd.h>
@@ -119,9 +118,7 @@ zed_file_is_locked(int fd)
 void
 zed_file_close_from(int lowfd)
 {
-	static const int maxfd_def = 256;
 	int errno_bak = errno;
-	struct rlimit rl;
 	int maxfd = 0;
 	int fd;
 	DIR *fddir;
@@ -134,11 +131,8 @@ zed_file_close_from(int lowfd)
 				maxfd = fd;
 		}
 		(void) closedir(fddir);
-	} else if (getrlimit(RLIMIT_NOFILE, &rl) < 0 ||
-	    rl.rlim_max == RLIM_INFINITY) {
-		maxfd = maxfd_def;
 	} else {
-		maxfd = rl.rlim_max;
+		maxfd = sysconf(_SC_OPEN_MAX);
 	}
 	for (fd = lowfd; fd < maxfd; fd++)
 		(void) close(fd);