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Subject[PATCH 5/6] core: allow setrlimit to non-current tasks
Date
Add locking to allow setrlimit accept task parameter other than
current.

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

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
---
kernel/sys.c | 26 ++++++++++++++++++++------
1 files changed, 20 insertions(+), 6 deletions(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index 919cebe..777a152 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1244,16 +1244,27 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,

if (new_rlim->rlim_cur > new_rlim->rlim_max)
return -EINVAL;
+
+ /* protect tsk->signal and tsk->sighand from disappearing */
+ read_lock_irq(&tasklist_lock);
+ if (!tsk->signal || !tsk->sighand) {
+ retval = -ESRCH;
+ goto unlock;
+ }
old_rlim = tsk->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;
+ !capable(CAP_SYS_RESOURCE)) {
+ retval = -EPERM;
+ goto unlock;
+ }
+ if (resource == RLIMIT_NOFILE && new_rlim->rlim_max > sysctl_nr_open) {
+ retval = -EPERM;
+ goto unlock;
+ }

retval = security_task_setrlimit(tsk, resource, new_rlim);
if (retval)
- return retval;
+ goto unlock;

if (resource == RLIMIT_CPU && new_rlim->rlim_cur == 0) {
/*
@@ -1283,7 +1294,10 @@ int setrlimit(struct task_struct *tsk, unsigned int resource,

update_rlimit_cpu(tsk, new_rlim->rlim_cur);
out:
- return 0;
+ retval = 0;
+unlock:
+ read_unlock_irq(&tasklist_lock);
+ return retval;
}

SYSCALL_DEFINE2(setrlimit, unsigned int, resource, struct rlimit __user *, rlim)
--
1.6.3.3


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