linux-kernel - [PATCH -repost 4/8] sys_setrlimit: make sure ->rlim

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <1255814482-13994-4-git-send-email-jirislaby@gmail.com>
Date:	Sat, 17 Oct 2009 23:21:18 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	akpm@...ux-foundation.org
Cc:	linux-kernel@...r.kernel.org, Oleg Nesterov <oleg@...hat.com>,
	Jiri Slaby <jirislaby@...il.com>
Subject: [PATCH -repost 4/8] sys_setrlimit: make sure ->rlim_max never grows

From: Oleg Nesterov <oleg@...hat.com>

Mostly preparation for Jiri's changes, but probably makes sense anyway.

sys_setrlimit() checks new_rlim.rlim_max <= old_rlim->rlim_max, but when
it takes task_lock() old_rlim->rlim_max can be already lowered. Move this
check under task_lock().

Currently this is not important, we can only race with our sub-thread,
this means the application is stupid. But when we change the code to allow
the update of !current task's limits, it becomes important to make sure
->rlim_max can be lowered "reliably" even if we race with the application
doing sys_setrlimit().

Signed-off-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Jiri Slaby <jirislaby@...il.com>
---
 kernel/sys.c |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index b8f9f13..4b3a966 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1249,10 +1249,6 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 		return -EFAULT;
 	if (new_rlim.rlim_cur > new_rlim.rlim_max)
 		return -EINVAL;
-	old_rlim = current->signal->rlim + resource;
-	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;
 
@@ -1270,11 +1266,16 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 		new_rlim.rlim_cur = 1;
 	}
 
+	old_rlim = current->signal->rlim + resource;
 	task_lock(current->group_leader);
-	*old_rlim = new_rlim;
+	if ((new_rlim.rlim_max <= old_rlim->rlim_max) ||
+				capable(CAP_SYS_RESOURCE))
+		*old_rlim = new_rlim;
+	else
+		retval = -EPERM;
 	task_unlock(current->group_leader);
 
-	if (resource != RLIMIT_CPU)
+	if (retval || resource != RLIMIT_CPU)
 		goto out;
 
 	/*
@@ -1288,7 +1289,7 @@ SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
 
 	update_rlimit_cpu(current, new_rlim.rlim_cur);
 out:
-	return 0;
+	return retval;
 }
 
 /*
-- 
1.6.4.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/