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Subject[PATCH v3 05/11] rlimits: allow setrlimit to non-current tasks
Date
From: Jiri Slaby <jirislaby@gmail.com>

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.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Cc: Oleg Nesterov <oleg@redhat.com>
---
kernel/sys.c | 11 ++++++++++-
1 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/kernel/sys.c b/kernel/sys.c
index 7c76f84..eb21661 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -1272,6 +1272,7 @@ SYSCALL_DEFINE2(old_getrlimit, unsigned int, resource,

#endif

+/* make sure you are allowed to change @tsk limits before calling this */
int do_setrlimit(struct task_struct *tsk, unsigned int resource,
struct rlimit *new_rlim)
{
@@ -1285,9 +1286,16 @@ int do_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) {
/*
@@ -1322,6 +1330,7 @@ int do_setrlimit(struct task_struct *tsk, unsigned int resource,

update_rlimit_cpu(tsk, new_rlim->rlim_cur);
out:
+ read_unlock(&tasklist_lock);
return retval;
}

--
1.7.1



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