linux-kernel - [PATCH v2 6/8] core: allow setrlimit to non-current tasks

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Date:	Thu,  3 Sep 2009 22:08:42 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	oleg@...hat.com
Cc:	akpm@...ux-foundation.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org, Jiri Slaby <jirislaby@...il.com>
Subject: [PATCH v2 6/8] core: allow setrlimit to non-current tasks

Add locking to allow setrlimit accept task parameter other than
current.

Namely, lock tasklist_lock for read and check whether the task
structure has sighand non-null. Do all the signal processing under
that lock still held. We do this only for non-current tasks.

Signed-off-by: Jiri Slaby <jirislaby@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>
---
 kernel/sys.c |   10 +++++++++-
 1 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 655dd7b..791b5c5 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1247,9 +1247,16 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,
 	if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open)
 		return -EPERM;
 
+	/* protect tsk->signal and tsk->sighand from disappearing */
+	read_lock(&tasklist_lock);
+	if (!tsk->sighand) {
+		retval = -ESRCH;
+		goto out;
+	}
+
 	retval = security_task_setrlimit(tsk, resource, new_rlim);
 	if (retval)
-		return retval;
+		goto out;
 
 	if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
 		/*
@@ -1284,6 +1291,7 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,
 
 	update_rlimit_cpu(tsk, new_rlim->rlim_cur);
 out:
+	read_unlock(&tasklist_lock);
 	return retval;
 }
 
-- 
1.6.3.3

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