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From: Hans Verkuil <hverkuil-cisco@xs4all.nl>
To: "Yang, Chenyuan" <cy54@illinois.edu>,
	"linux-media@vger.kernel.org" <linux-media@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "jani.nikula@intel.com" <jani.nikula@intel.com>,
	"syzkaller@googlegroups.com" <syzkaller@googlegroups.com>,
	"mchehab@kernel.org" <mchehab@kernel.org>,
	"Zhao, Zijie" <zijie4@illinois.edu>,
	"Zhang, Lingming" <lingming@illinois.edu>
Subject: Re: [Linux Kernel Bugs] KASAN: slab-use-after-free Read in cec_queue_msg_fh and 4 other crashes in the cec device (`cec_ioctl`)
Date: Tue, 30 Apr 2024 12:26:40 +0200	[thread overview]
Message-ID: <ace1b749-9a4d-4c68-b5a7-530e0d3ff504@xs4all.nl> (raw)
In-Reply-To: <CA3D308A-ED29-440C-A6C5-C5450CDA2C84@illinois.edu>

Hi Chenyuan,

On 29/04/2024 17:42, Yang, Chenyuan wrote:
> Hi Hans,
> 
> Here is my QEMU booting command:
> 
> ```
> qemu-system-x86_64 \
> 	-m 2G \
> 	-smp 2 \
> 	-kernel linux/arch/x86/boot/bzImage \
> 	-append "console=ttyS0 root=/dev/sda earlyprintk=serial net.ifnames=0" \
> 	-drive file=image/bullseye-qemu.img,format=raw \
> 	-net user,host=10.0.2.10,hostfwd=tcp:127.0.0.1:10021-:22 \
> 	-net nic,model=e1000 \
> 	-enable-kvm \
> 	-nographic \
> 	-pidfile vm.pi
> ```
> 
> Plus, here is the config of vivid from my linux kernel building config:
> 
> ```
> CONFIG_VIDEO_VIVID=y
> CONFIG_VIDEO_VIVID_CEC=y
> CONFIG_VIDEO_VIVID_MAX_DEVS=64
> 
> CONFIG_CMDLINE="... vivid.n_devs=16 vivid.multiplanar=1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2 ..."
> 
> # Here is the full
> CONFIG_CMDLINE="earlyprintk=serial net.ifnames=0 sysctl.kernel.hung_task_all_cpu_backtrace=1 ima_policy=tcb nf-conntrack-ftp.ports=20000 nf-conntrack-tftp.ports=20000 nf-conntrack-sip.ports=20000 nf-conntrack-irc.ports=20000 nf-conntrack-sane.ports=20000 binder.debug_mask=0 rcupdate.rcu_expedited=1 rcupdate.rcu_cpu_stall_cputime=1 no_hash_pointers page_owner=on sysctl.vm.nr_hugepages=4 sysctl.vm.nr_overcommit_hugepages=4 secretmem.enable=1 sysctl.max_rcu_stall_to_panic=1 msr.allow_writes=off coredump_filter=0xffff root=/dev/sda console=ttyS0 vsyscall=native numa=fake=2 kvm-intel.nested=1 spec_store_bypass_disable=prctl nopcid vivid.n_devs=16 vivid.multiplanar=1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2 netrom.nr_ndevs=16 rose.rose_ndevs=16 smp.csd_lock_timeout=100000 watchdog_thresh=55 workqueue.watchdog_thresh=140 sysctl.net.core.netdev_unregister_timeout_secs=140 dummy_hcd.num=8 kmsan.panic=1"
> ```
> 
> Plus, I attached the current patch (git diff > patch).
> 
> Let me know if you need any further information.

Ah, that was helpful. I also discovered that I had to run the reproducer as root,
that helped too :-)

Please add this patch on top of the diff you already have and try again.

The reproducer kills each forked process after 5 seconds from what I can
tell. That causes a driver wait call to return -ERESTARTSYS, and that corner
case was not handled correctly. It caused the harmless but confusing
"transmit timed out" message.

Regards,

	Hans

---------------------------------------------------------------------
[PATCH] cec: core: avoid confusing "transmit timed out" message

If, when waiting for a transmit to finish, the wait is interrupted,
then you might get a "transmit timed out" message, even though the
transmit was interrupted and did not actually time out.

Set transmit_in_progress_aborted to true if the
wait_for_completion_killable() call was interrupted and ensure
that the transmit is properly marked as ABORTED.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 drivers/media/cec/core/cec-adap.c | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/media/cec/core/cec-adap.c b/drivers/media/cec/core/cec-adap.c
index a493cbce24567..da09834990b87 100644
--- a/drivers/media/cec/core/cec-adap.c
+++ b/drivers/media/cec/core/cec-adap.c
@@ -490,6 +490,15 @@ int cec_thread_func(void *_adap)
 			goto unlock;
 		}

+		if (adap->transmit_in_progress &&
+		    adap->transmit_in_progress_aborted) {
+			if (adap->transmitting)
+				cec_data_cancel(adap->transmitting,
+						CEC_TX_STATUS_ABORTED, 0);
+			adap->transmit_in_progress = false;
+			adap->transmit_in_progress_aborted = false;
+			goto unlock;
+		}
 		if (adap->transmit_in_progress && timeout) {
 			/*
 			 * If we timeout, then log that. Normally this does
@@ -771,6 +780,7 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,
 {
 	struct cec_data *data;
 	bool is_raw = msg_is_raw(msg);
+	int err;

 	if (adap->devnode.unregistered)
 		return -ENODEV;
@@ -935,10 +945,13 @@ int cec_transmit_msg_fh(struct cec_adapter *adap, struct cec_msg *msg,
 	 * Release the lock and wait, retake the lock afterwards.
 	 */
 	mutex_unlock(&adap->lock);
-	wait_for_completion_killable(&data->c);
+	err = wait_for_completion_killable(&data->c);
 	cancel_delayed_work_sync(&data->work);
 	mutex_lock(&adap->lock);

+	if (err)
+		adap->transmit_in_progress_aborted = true;
+
 	/* Cancel the transmit if it was interrupted */
 	if (!data->completed) {
 		if (data->msg.tx_status & CEC_TX_STATUS_OK)
-- 
2.43.0



  reply	other threads:[~2024-04-30 10:26 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-12-28  2:33 [Linux Kernel Bugs] KASAN: slab-use-after-free Read in cec_queue_msg_fh and 4 other crashes in the cec device (`cec_ioctl`) Yang, Chenyuan
2023-12-29  6:23 ` Dmitry Vyukov
     [not found] ` <SN6PR11MB345527101A2C8A1AC99B04B5FA712@SN6PR11MB3455.namprd11.prod.outlook.com>
2024-01-18  7:52   ` Hans Verkuil
2024-01-19  8:17 ` Hans Verkuil
2024-01-22 19:11   ` Yang, Chenyuan
2024-01-23  8:02     ` Hans Verkuil
2024-01-23 10:39       ` Hans Verkuil
2024-01-24 13:33   ` Yang, Chenyuan
2024-01-25 10:35     ` Hans Verkuil
2024-01-29  3:03   ` Yang, Chenyuan
2024-01-30 14:35     ` Hans Verkuil
2024-02-12 14:42       ` Hans Verkuil
2024-02-13 15:40         ` Yang, Chenyuan
2024-02-13 16:05           ` Yang, Chenyuan
2024-02-23 14:44           ` Hans Verkuil
     [not found]             ` <PH7PR11MB5768B0BC3C042A6EA4EC1EF0A0542@PH7PR11MB5768.namprd11.prod.outlook.com>
2024-02-26 12:27               ` Yang, Chenyuan
2024-04-19 14:51                 ` Takashi Iwai
2024-04-22 12:14                   ` Hans Verkuil
2024-04-22 19:30                     ` Takashi Iwai
2024-04-22 15:04                 ` Hans Verkuil
2024-04-22 18:54                   ` Yang, Chenyuan
2024-04-22 20:57                     ` Hans Verkuil
2024-04-29 15:42                       ` Yang, Chenyuan
2024-04-30 10:26                         ` Hans Verkuil [this message]
2024-04-30 17:06                           ` Yang, Chenyuan

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