Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH v4 06/12] rlimits: allow setrlimit to non-current tasks | Date | Wed, 23 Jun 2010 23:52:07 +0200 |
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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.
There are some points: 1) security_task_setrlimit is now called with that lock held. This is not new, many security_* functions are called with this lock held already so it doesn't harm (all this security_* stuff does almost the same). 2) task->sighand->siglock (in update_rlimit_cpu) is nested in tasklist_lock. This dependence is already existing. 3) tsk->alloc_lock is nested in tasklist_lock. This is OK too, already existing dependence.
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 b5b96e3..9dbcbbc 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->group_leader, 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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