From 6a0b95be233536f85ffb900c29ff773f47be1208 Mon Sep 17 00:00:00 2001 From: Eric Paris Date: Wed, 19 Jun 2013 10:08:21 +1000 Subject: [PATCH] fork: reorder permissions when violating number of processes limits When a task is attempting to violate the RLIMIT_NPROC limit we have a check to see if the task is sufficiently priviledged. The check first looks at CAP_SYS_ADMIN, then CAP_SYS_RESOURCE, then if the task is uid=0. A result is that tasks which are allowed by the uid=0 check are first checked against the security subsystem. This results in the security subsystem auditting a denial for sys_admin and sys_resource and then the task passing the uid=0 check. This patch rearranges the code to first check uid=0, since if we pass that we shouldn't hit the security system at all. We then check sys_resource, since it is the smallest capability which will solve the problem. Lastly we check the fallback everything cap_sysadmin. We don't want to give this capability many places since it is so powerful. This will eliminate many of the false positive/needless denial messages we get when a root task tries to violate the nproc limit. (note that kthreads count against root, so on a sufficiently large machine we can actually get past the default limits before any userspace tasks are launched.) Signed-off-by: Eric Paris Cc: Al Viro Signed-off-by: Andrew Morton --- kernel/fork.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 6fcc2e24561e..7fe4203cfe68 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1195,8 +1195,8 @@ static struct task_struct *copy_process(unsigned long clone_flags, retval = -EAGAIN; if (atomic_read(&p->real_cred->user->processes) >= task_rlimit(p, RLIMIT_NPROC)) { - if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && - p->real_cred->user != INIT_USER) + if (p->real_cred->user != INIT_USER && + !capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) goto bad_fork_free; } current->flags &= ~PF_NPROC_EXCEEDED; -- 2.39.5