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Subject[PATCH v4 07/12] rlimits: do security check under task_lock
Date
Do security_task_setrlimit under task_lock. Other tasks may change
limits under our hands while we are checking limits inside the
function. From now on, they can't.

Note that all the security work is done under a spinlock here now.
Security hooks count with that, they are called from interrupt context
(like security_task_kill) and with spinlocks already held (e.g.
capable->security_capable).

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Acked-by: James Morris <jmorris@namei.org>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
---
kernel/sys.c | 20 ++++++++++----------
1 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 9dbcbbc..c762eeb 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1277,7 +1277,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
struct rlimit *new_rlim)
{
struct rlimit *old_rlim;
- int retval;
+ int retval = 0;

if (resource >= RLIM_NLIMITS)
return -EINVAL;
@@ -1293,9 +1293,14 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
goto out;
}

- retval = security_task_setrlimit(tsk->group_leader, resource, new_rlim);
- if (retval)
- goto out;
+ old_rlim = tsk->signal->rlim + resource;
+ task_lock(tsk->group_leader);
+ if (new_rlim->rlim_max > old_rlim->rlim_max &&
+ !capable(CAP_SYS_RESOURCE))
+ retval = -EPERM;
+ if (!retval)
+ retval = security_task_setrlimit(tsk->group_leader, resource,
+ new_rlim);

if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
/*
@@ -1307,12 +1312,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,
new_rlim->rlim_cur = 1;
}

- old_rlim = tsk->signal->rlim + resource;
- task_lock(tsk->group_leader);
- if (new_rlim->rlim_max > old_rlim->rlim_max &&
- !capable(CAP_SYS_RESOURCE))
- retval = -EPERM;
- else
+ if (!retval)
*old_rlim = *new_rlim;
task_unlock(tsk->group_leader);

--
1.7.1



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