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Date: Fri, 4 May 2007 09:14:34 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Greg KH <greg@...ah.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Hugh Dickins <hugh@...itas.com>,
Christoph Lameter <clameter@...r.sgi.com>,
"David S. Miller" <davem@...emloft.net>, Andi Kleen <ak@...e.de>,
"Luck, Tony" <tony.luck@...el.com>, Rik van Riel <riel@...hat.com>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
Roland McGrath <roland@...hat.com>,
Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: incoming
On Fri, 4 May 2007 06:37:28 -0700 Greg KH <greg@...ah.com> wrote:
> On Wed, May 02, 2007 at 03:02:52PM -0700, Andrew Morton wrote:
> > - One little security patch
>
> Care to cc: linux-stable with it so we can do a new 2.6.21 release with
> it if needed?
>
Ah. The patch affects security code, but it doesn't actually address any
insecurity. I didn't think it was needed for -stable?
From: Roland McGrath <roland@...hat.com>
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@...ei.org: switch error code to EACCES]
Signed-off-by: Roland McGrath <roland@...hat.com>
Cc: Stephen Smalley <sds@...ho.nsa.gov>
Cc: Chris Wright <chrisw@...s-sol.org>
Cc: James Morris <jmorris@...ei.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---
kernel/exit.c | 17 +++++++++++++++--
1 files changed, 15 insertions(+), 2 deletions(-)
diff -puN kernel/exit.c~return-eperm-not-echild-on-security_task_wait-failure kernel/exit.c
--- a/kernel/exit.c~return-eperm-not-echild-on-security_task_wait-failure
+++ a/kernel/exit.c
@@ -1033,6 +1033,8 @@ asmlinkage void sys_exit_group(int error
static int eligible_child(pid_t pid, int options, struct task_struct *p)
{
+ int err;
+
if (pid > 0) {
if (p->pid != pid)
return 0;
@@ -1066,8 +1068,9 @@ static int eligible_child(pid_t pid, int
if (delay_group_leader(p))
return 2;
- if (security_task_wait(p))
- return 0;
+ err = security_task_wait(p);
+ if (err)
+ return err;
return 1;
}
@@ -1449,6 +1452,7 @@ static long do_wait(pid_t pid, int optio
DECLARE_WAITQUEUE(wait, current);
struct task_struct *tsk;
int flag, retval;
+ int allowed, denied;
add_wait_queue(¤t->signal->wait_chldexit,&wait);
repeat:
@@ -1457,6 +1461,7 @@ repeat:
* match our criteria, even if we are not able to reap it yet.
*/
flag = 0;
+ allowed = denied = 0;
current->state = TASK_INTERRUPTIBLE;
read_lock(&tasklist_lock);
tsk = current;
@@ -1472,6 +1477,12 @@ repeat:
if (!ret)
continue;
+ if (unlikely(ret < 0)) {
+ denied = ret;
+ continue;
+ }
+ allowed = 1;
+
switch (p->state) {
case TASK_TRACED:
/*
@@ -1570,6 +1581,8 @@ check_continued:
goto repeat;
}
retval = -ECHILD;
+ if (unlikely(denied) && !allowed)
+ retval = denied;
end:
current->state = TASK_RUNNING;
remove_wait_queue(¤t->signal->wait_chldexit,&wait);
_
-
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