From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org,
linux-rt-users <linux-rt-users@vger.kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Carsten Emde <C.Emde@osadl.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
John Kacur <jkacur@redhat.com>, Daniel Wagner <wagi@monom.org>,
Tom Zanussi <zanussi@kernel.org>,
"Srivatsa S. Bhat" <srivatsa@csail.mit.edu>,
Matt Fleming <matt@codeblueprint.co.uk>
Subject: [PATCH RT 1/6] signal: Prevent double-free of user struct
Date: Wed, 12 Aug 2020 21:45:35 -0400 [thread overview]
Message-ID: <20200813014555.384329363@goodmis.org> (raw)
In-Reply-To: 20200813014534.833107526@goodmis.org
5.4.54-rt33-rc1 stable review patch.
If anyone has any objections, please let me know.
------------------
From: Matt Fleming <matt@codeblueprint.co.uk>
The way user struct reference counting works changed significantly with,
fda31c50292a ("signal: avoid double atomic counter increments for user accounting")
Now user structs are only freed once the last pending signal is
dequeued. Make sigqueue_free_current() follow this new convention to
avoid freeing the user struct multiple times and triggering this
warning:
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 6794 at lib/refcount.c:288 refcount_dec_not_one+0x45/0x50
Call Trace:
refcount_dec_and_lock_irqsave+0x16/0x60
free_uid+0x31/0xa0
__dequeue_signal+0x17c/0x190
dequeue_signal+0x5a/0x1b0
do_sigtimedwait+0x208/0x250
__x64_sys_rt_sigtimedwait+0x6f/0xd0
do_syscall_64+0x72/0x200
entry_SYSCALL_64_after_hwframe+0x49/0xbe
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Reported-by: Daniel Wagner <wagi@monom.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/signal.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/signal.c b/kernel/signal.c
index def2e8e37f1f..aa924f0141cf 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -494,8 +494,8 @@ static void sigqueue_free_current(struct sigqueue *q)
up = q->user;
if (rt_prio(current->normal_prio) && !put_task_cache(current, q)) {
- atomic_dec(&up->sigpending);
- free_uid(up);
+ if (atomic_dec_and_test(&up->sigpending))
+ free_uid(up);
} else
__sigqueue_free(q);
}
--
2.28.0
next prev parent reply other threads:[~2020-08-13 1:46 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-13 1:45 [PATCH RT 0/6] Linux 5.4.54-rt33-rc1 Steven Rostedt
2020-08-13 1:45 ` Steven Rostedt [this message]
2020-08-13 8:25 ` [PATCH RT 1/6] signal: Prevent double-free of user struct Rasmus Villemoes
2020-08-13 19:28 ` Steven Rostedt
2020-08-13 1:45 ` [PATCH RT 2/6] workqueue: Sync with upstream Steven Rostedt
2020-08-13 1:45 ` [PATCH RT 3/6] Bluetooth: Acquire sk_lock.slock without disabling interrupts Steven Rostedt
2020-08-13 1:45 ` [PATCH RT 4/6] net: phy: fixed_phy: Remove unused seqcount Steven Rostedt
2020-08-13 1:45 ` [PATCH RT 5/6] rwsem: Provide down_read_non_owner() and up_read_non_owner() for -RT Steven Rostedt
2020-08-13 1:45 ` [PATCH RT 6/6] Linux 5.4.54-rt33-rc1 Steven Rostedt
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