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([2405:4802:1d4a:e90:3a0c:2ea9:4ab7:bd1b]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a0b9356f48sm13557768a91.6.2026.09.26.23.10.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 26 Sep 2026 23:10:12 -0700 (PDT) From: Nguyen Ngoc Thang To: Mauro Carvalho Chehab , Antti Palosaari Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Nguyen Ngoc Thang , syzbot+c35815bad054e6ad396e@syzkaller.appspotmail.com, stable@vger.kernel.org Subject: [PATCH v2] media: dvb-usb-v2: set active_fe before the demux goes live Date: Sun, 27 Sep 2026 13:10:08 +0700 Message-ID: <20260927061008.47318-1-ngocthang2710.1999@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260927044547.26979-1-ngocthang2710.1999@gmail.com> References: <20260927044547.26979-1-ngocthang2710.1999@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit dvb_usbv2_adapter_dvb_init() registers the demux devices before dvb_usbv2_adapter_frontend_init() runs. Only the latter set adap->active_fe to -1, so until then it holds the kzalloc'ed 0 while adap->fe[0] is still NULL. A process that opens the demux and starts a filter in that window, which lasts as long as frontend_attach() takes, gets past the active_fe == -1 check in dvb_usb_start_feed() and passes the NULL adap->fe[0] to streaming_ctrl() (or get_stream_config()). mxl111sf_ep6_streaming_ctrl() then dereferences it: Oops: general protection fault, probably for non-canonical address 0xdffffc0000000061 KASAN: null-ptr-deref in range [0x0000000000000308-0x000000000000030f] RIP: 0010:mxl111sf_ep6_streaming_ctrl+0x2e/0x2e0 dvb_usb_start_feed+0x57a/0xc70 dmx_ts_feed_start_filtering+0x129/0x220 dvb_dmxdev_filter_start+0x434/0x10d0 dvb_demux_do_ioctl+0x48b/0x540 Initialise active_fe to -1 before the demux is registered so early feeds fail with -EINVAL. Reported-by: syzbot+c35815bad054e6ad396e@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=c35815bad054e6ad396e Fixes: ad6b9e517b39 ("[media] dvb_usb_v2: move from dvb-usb to dvb-usb-v2") Cc: stable@vger.kernel.org Signed-off-by: Nguyen Ngoc Thang --- drivers/media/usb/dvb-usb-v2/dvb_usb_core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c index bd86d250433d..557451b541e6 100644 --- a/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c +++ b/drivers/media/usb/dvb-usb-v2/dvb_usb_core.c @@ -637,7 +637,6 @@ static int dvb_usbv2_adapter_frontend_init(struct dvb_usb_adapter *adap) dev_dbg(&d->udev->dev, "%s: adap=%d\n", __func__, adap->id); memset(adap->fe, 0, sizeof(adap->fe)); - adap->active_fe = -1; if (d->props->frontend_attach) { ret = d->props->frontend_attach(adap); @@ -795,6 +794,9 @@ static int dvb_usbv2_adapter_init(struct dvb_usb_device *d) adap->max_feed_count = adap->props->pid_filter_count; } + /* demux is live before frontends attach: no feed until then */ + adap->active_fe = -1; + ret = dvb_usbv2_adapter_stream_init(adap); if (ret) goto err; -- 2.43.0