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Wed, 26 Aug 2026 20:52:11 -0700 (PDT) From: Jeffin Philip To: jeffinphilip14@gmail.com Cc: hverkuil+cisco@kernel.org, kees@kernel.org, linma@zju.edu.cn, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, mchehab@kernel.org, ribalda@chromium.org, sakari.ailus@linux.intel.com, stable@vger.kernel.org, syzbot+37578f730d38898f4b74@syzkaller.appspotmail.com Subject: Re: [PATCH] media: dvbdev: fix uaf in dvb_remove_device() Date: Thu, 27 Aug 2026 09:21:55 +0530 Message-ID: <20260827035155.10725-1-jeffinphilip14@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260822112256.12346-1-jeffinphilip14@gmail.com> References: <20260822112256.12346-1-jeffinphilip14@gmail.com> Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On Sat, 22 Aug 2026 16:52:56 +0530, Jeffin Philip wrote: >In dvb_remove_device(), dvb_media_device_free(), device_destroy() >and list_del() all dereference dvbdev regardless of its refcount. >Thus, if refcount for dvbdev is 1, it can be freed and we >operate on freed memory causing a UAF. Fix this by moving >dvb_device_put() at the end of dvb_remove_device() so dvbdev >members can be safely freed and assigned NULL when dvbdev is alive. > >Reported-by: syzbot+37578f730d38898f4b74@syzkaller.appspotmail.com >Closes: https://syzkaller.appspot.com/bug?extid=37578f730d38898f4b74 >Fixes: 0fc044b2b5e2 ("media: dvbdev: adopts refcnt to avoid UAF") >Cc: stable@vger.kernel.org >Signed-off-by: Jeffin Philip >--- > drivers/media/dvb-core/dvbdev.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > >diff --git a/drivers/media/dvb-core/dvbdev.c b/drivers/media/dvb-core/dvbdev.c >index d753d329502a..9aa4b8fd7379 100644 >--- a/drivers/media/dvb-core/dvbdev.c >+++ b/drivers/media/dvb-core/dvbdev.c >@@ -598,7 +598,6 @@ void dvb_remove_device(struct dvb_device *dvbdev) > > down_write(&minor_rwsem); > dvb_minors[dvbdev->minor] = NULL; >- dvb_device_put(dvbdev); > up_write(&minor_rwsem); > > dvb_media_device_free(dvbdev); >@@ -606,6 +605,8 @@ void dvb_remove_device(struct dvb_device *dvbdev) > device_destroy(dvb_class, MKDEV(DVB_MAJOR, dvbdev->minor)); > > list_del(&dvbdev->list_head); >+ >+ dvb_device_put(dvbdev); > } > EXPORT_SYMBOL(dvb_remove_device); > >-- Friendly ping, let me know if you want me to fix anything. Thanks, Jeffin.