linux-kernel - [PATCH] pid: Fix error return value in some cases

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Message-Id: <20200306152001.30442-1-minyard@acm.org>
Date:   Fri,  6 Mar 2020 09:20:01 -0600
From:   minyard@....org
To:     linux-kernel@...r.kernel.org
Cc:     Corey Minyard <cminyard@...sta.com>, stable@...r.kernel.org,
        Adrian Reber <areber@...hat.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Dmitry Safonov <0x7f454c46@...il.com>,
        Andrei Vagin <avagin@...il.com>
Subject: [PATCH] pid: Fix error return value in some cases

From: Corey Minyard <cminyard@...sta.com>

Recent changes to alloc_pid() allow the pid number to be specified on
the command line.  If set_tid_size is set, then the code scanning the
levels will hard-set retval to -EPERM, overriding it's previous -ENOMEM
value.

After the code scanning the levels, there are error returns that do not
set retval, assuming it is still set to -ENOMEM.

In the first place, pid_ns_prepare_proc() returns its own error, just
use that.

In the second place:

	if (!(ns->pid_allocated & PIDNS_ADDING))
		goto out_unlock;

a return value of -ENOMEM is probably wrong, since that means that the
namespace is in deletion while this happened.  -EINVAL is probably a
better choice.

Fixes: 49cb2fc42ce4 "fork: extend clone3() to support setting a PID"
Signed-off-by: Corey Minyard <cminyard@...sta.com>
Cc: <stable@...r.kernel.org> # 5.5
Cc: Adrian Reber <areber@...hat.com>
Cc: Christian Brauner <christian.brauner@...ntu.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Dmitry Safonov <0x7f454c46@...il.com>
Cc: Andrei Vagin <avagin@...il.com>
Cc: Christian Brauner <christian.brauner@...ntu.com>
---
 kernel/pid.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/kernel/pid.c b/kernel/pid.c
index 0f4ecb57214c..1921f7f4b236 100644
--- a/kernel/pid.c
+++ b/kernel/pid.c
@@ -248,7 +248,8 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 	}
 
 	if (unlikely(is_child_reaper(pid))) {
-		if (pid_ns_prepare_proc(ns))
+		retval = pid_ns_prepare_proc(ns);
+		if (retval)
 			goto out_free;
 	}
 
@@ -261,8 +262,10 @@ struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
 
 	upid = pid->numbers + ns->level;
 	spin_lock_irq(&pidmap_lock);
-	if (!(ns->pid_allocated & PIDNS_ADDING))
+	if (!(ns->pid_allocated & PIDNS_ADDING)) {
+		retval = -EINVAL;
 		goto out_unlock;
+	}
 	for ( ; upid >= pid->numbers; --upid) {
 		/* Make the PID visible to find_pid_ns. */
 		idr_replace(&upid->ns->idr, pid, upid->nr);
-- 
2.17.1