linux-kernel - [PATCH 2.6.27-rc5] Allow set RLIMIT_NOFILE to RLIM

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Date:	Fri, 12 Sep 2008 13:06:39 +0200
From:	Adam Tkac <vonsch@...il.com>
To:	torvalds@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mtk.manpages@...il.com
Subject: [PATCH 2.6.27-rc5] Allow set RLIMIT_NOFILE to RLIM_INFINITY

When a process wants to set the limit of open files to RLIM_INFINITY it
gets EPERM even if it has CAP_SYS_RESOURCE capability.
 
For example, BIND does:

...
#elif defined(NR_OPEN) && defined(__linux__)
        /*
         * Some Linux kernels don't accept RLIM_INFINIT; the maximum
         * possible value is the NR_OPEN defined in linux/fs.h.
         */
        if (resource == isc_resource_openfiles && rlim_value == RLIM_INFINITY) {
                rl.rlim_cur = rl.rlim_max = NR_OPEN;
                unixresult = setrlimit(unixresource, &rl);
                if (unixresult == 0)
                        return (ISC_R_SUCCESS);
        }
#elif ...

If we allow setting RLIMIT_NOFILE to RLIM_INFINITY we increase portability
- you don't have to check if OS is linux and then use different schema for
limits.

The spec says "Specifying RLIM_INFINITY as any resource limit value on a
successful call to setrlimit() shall inhibit enforcement of that resource
limit." and we're presently not doing that.

Cc: Michael Kerrisk <mtk.manpages@...glemail.com>
Signed-off-by: Adam Tkac <vonsch@...il.com>
Tested-by: Adam Tkac <vonsch@...il.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 kernel/sys.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff -puN kernel/sys.c~rlimit-permit-setting-rlimit_nofile-to-rlim_infinity kernel/sys.c
--- a/kernel/sys.c~rlimit-permit-setting-rlimit_nofile-to-rlim_infinity
+++ a/kernel/sys.c
@@ -1532,8 +1532,14 @@ asmlinkage long sys_setrlimit(unsigned i
 	if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
 	    !capable(CAP_SYS_RESOURCE))
 		return -EPERM;
-	if (resource == RLIMIT_NOFILE && new_rlim.rlim_max > sysctl_nr_open)
-		return -EPERM;
+	if (resource == RLIMIT_NOFILE) {
+		if (new_rlim.rlim_max == RLIM_INFINITY)
+			new_rlim.rlim_max = sysctl_nr_open;
+		if (new_rlim.rlim_cur == RLIM_INFINITY)
+			new_rlim.rlim_cur = sysctl_nr_open;
+		if (new_rlim.rlim_max > sysctl_nr_open)
+			return -EPERM;
+	}
 
 	retval = security_task_setrlimit(resource, &new_rlim);
 	if (retval)
--
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