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authorOleg Nesterov <oleg@tv-sign.ru>2008-02-08 04:19:06 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2008-02-08 09:22:26 -0800
commitf2cc3eb133baa2e9dc8efd40f417106b2ee520f3 (patch)
tree37b08158ee5296e79a61aad086be36c742825e3b /kernel/exit.c
parent96fabbf55ae79826f2e8a86f4066d7e8834315ae (diff)
downloadlinux-f2cc3eb133baa2e9dc8efd40f417106b2ee520f3.tar.gz
do_wait: fix security checks
Imho, the current usage of security_task_wait() is not logical. Suppose we have the single child p, and security_task_wait(p) return -EANY. In that case waitpid(-1) returns this error. Why? Isn't it better to return ECHLD? We don't really have reapable children. Now suppose that child was stolen by gdb. In that case we find this child on ->ptrace_children and set flag = 1, but we don't check that the child was denied. So, do_wait(..., WNOHANG) returns 0, this doesn't match the behaviour above. Without WNOHANG do_wait() blocks only to return the error later, when the child will be untraced. Inho, really strange. I think eligible_child() should return the error only if the child's pid was requested explicitly, otherwise we should silently ignore the tasks which were nacked by security_task_wait(). Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Cc: Roland McGrath <roland@redhat.com> Cc: Chris Wright <chrisw@sous-sol.org> Cc: Eric Paris <eparis@redhat.com> Cc: James Morris <jmorris@namei.org> Cc: Stephen Smalley <sds@tycho.nsa.gov> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/exit.c')
-rw-r--r--kernel/exit.c39
1 files changed, 18 insertions, 21 deletions
diff --git a/kernel/exit.c b/kernel/exit.c
index 9ee229ea97e..ee607720ae5 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1142,10 +1142,14 @@ static int eligible_child(pid_t pid, int options, struct task_struct *p)
return 0;
err = security_task_wait(p);
- if (err)
- return err;
+ if (likely(!err))
+ return 1;
- return 1;
+ if (pid <= 0)
+ return 0;
+ /* This child was explicitly requested, abort */
+ read_unlock(&tasklist_lock);
+ return err;
}
static int wait_noreap_copyout(struct task_struct *p, pid_t pid, uid_t uid,
@@ -1476,7 +1480,6 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int flag, retval;
- int allowed, denied;
add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat:
@@ -1484,8 +1487,7 @@ repeat:
* We will set this flag if we see any child that might later
* match our criteria, even if we are not able to reap it yet.
*/
- flag = 0;
- allowed = denied = 0;
+ flag = retval = 0;
current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
tsk = current;
@@ -1498,13 +1500,8 @@ repeat:
continue;
if (unlikely(ret < 0)) {
- denied = ret;
- continue;
- }
- allowed = 1;
-
- retval = 0;
- if (task_is_stopped_or_traced(p)) {
+ retval = ret;
+ } else if (task_is_stopped_or_traced(p)) {
/*
* It's stopped now, so it might later
* continue, exit, or stop again.
@@ -1544,11 +1541,14 @@ repeat:
}
if (!flag) {
list_for_each_entry(p, &tsk->ptrace_children,
- ptrace_list) {
- if (!eligible_child(pid, options, p))
+ ptrace_list) {
+ flag = eligible_child(pid, options, p);
+ if (!flag)
continue;
- flag = 1;
- break;
+ if (likely(flag > 0))
+ break;
+ retval = flag;
+ goto end;
}
}
if (options & __WNOTHREAD)
@@ -1556,10 +1556,9 @@ repeat:
tsk = next_thread(tsk);
BUG_ON(tsk->signal != current->signal);
} while (tsk != current);
-
read_unlock(&tasklist_lock);
+
if (flag) {
- retval = 0;
if (options & WNOHANG)
goto end;
retval = -ERESTARTSYS;
@@ -1569,8 +1568,6 @@ repeat:
goto repeat;
}
retval = -ECHILD;
- if (unlikely(denied) && !allowed)
- retval = denied;
end:
current->state = TASK_RUNNING;
remove_wait_queue(&current->signal->wait_chldexit,&wait);