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Return EPERM not ECHILD on security_task_wait failure

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wait* syscalls return -ECHILD even when an individual PID of a live child
was requested explicitly, when security_task_wait denies the operation.
This means that something like a broken SELinux policy can produce an
unexpected failure that looks just like a bug with wait or ptrace or
something.

This patch makes do_wait return -EACCES (or other appropriate error returned
from security_task_wait() instead of -ECHILD if some children were ruled out
solely because security_task_wait failed.

[jmorris@namei.org: switch error code to EACCES]
Signed-off-by: Roland McGrath <roland@redhat.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Roland McGrath 2007-05-06 14:50:20 -07:00 committed by Linus Torvalds
parent 906e0be197
commit 7324328446
1 changed files with 15 additions and 2 deletions
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17
kernel/exit.c
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@ -1033,6 +1033,8 @@ asmlinkage void sys_exit_group(int error_code)
static int eligible_child(pid_t pid, int options, struct task_struct *p) static int eligible_child(pid_t pid, int options, struct task_struct *p)
{ {
int err;
if (pid > 0) { if (pid > 0) {
if (p->pid != pid) if (p->pid != pid)
return 0; return 0;
@ -1066,8 +1068,9 @@ static int eligible_child(pid_t pid, int options, struct task_struct *p)
if (delay_group_leader(p)) if (delay_group_leader(p))
return 2; return 2;
if (security_task_wait(p)) err = security_task_wait(p);
return 0; if (err)
return err;
return 1; return 1;
} }
@ -1449,6 +1452,7 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
DECLARE_WAITQUEUE(wait, current); DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk; struct task_struct *tsk;
int flag, retval; int flag, retval;
int allowed, denied;
add_wait_queue(&current->signal->wait_chldexit,&wait); add_wait_queue(&current->signal->wait_chldexit,&wait);
repeat: repeat:
@ -1457,6 +1461,7 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
* match our criteria, even if we are not able to reap it yet. * match our criteria, even if we are not able to reap it yet.
*/ */
flag = 0; flag = 0;
allowed = denied = 0;
current->state = TASK_INTERRUPTIBLE; current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock); read_lock(&tasklist_lock);
tsk = current; tsk = current;
@ -1472,6 +1477,12 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
if (!ret) if (!ret)
continue; continue;
if (unlikely(ret < 0)) {
denied = ret;
continue;
}
allowed = 1;
switch (p->state) { switch (p->state) {
case TASK_TRACED: case TASK_TRACED:
/* /*
@ -1570,6 +1581,8 @@ static long do_wait(pid_t pid, int options, struct siginfo __user *infop,
goto repeat; goto repeat;
} }
retval = -ECHILD; retval = -ECHILD;
if (unlikely(denied) && !allowed)
retval = denied;
end: end:
current->state = TASK_RUNNING; current->state = TASK_RUNNING;
remove_wait_queue(&current->signal->wait_chldexit,&wait); remove_wait_queue(&current->signal->wait_chldexit,&wait);