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Thu, 13 Aug 2026 22:26:24 -0700 (PDT) From: "Cen Zhang (Microsoft)" To: mchehab@kernel.org, hverkuil@kernel.org Cc: kees@kernel.org, rongqianfeng@vivo.com, axboe@kernel.dk, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, AutonomousCodeSecurity@microsoft.com, tgopinath@linux.microsoft.com, kys@microsoft.com, blbllhy@gmail.com, stable@vger.kernel.org Subject: [PATCH v3] media: dvb-core: add upper bound check in DMX_SET_BUFFER_SIZE ioctl Date: Fri, 14 Aug 2026 01:26:08 -0400 Message-ID: <20260814052608.39361-1-blbllhy@gmail.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit dvb_dvr_set_buffer_size() and dvb_dmxdev_set_buffer_size() pass the user-supplied size argument directly to vmalloc() without any upper bound check. This allows excessive kernel memory allocation via the DMX_SET_BUFFER_SIZE ioctl, which can lead to system-wide OOM conditions. Kernel panic - not syncing: System is deadlocked on memory Call Trace: out_of_memory+0x12fd/0x1370 __alloc_frozen_pages_noprof+0x2620/0x2fa0 __vmalloc_node_range_noprof+0x7fa/0x1490 dvb_dvr_do_ioctl+0x11e/0x260 (drivers/media/dvb-core/dmxdev.c:296) dvb_usercopy+0x15b/0x360 Fix by clamping both functions to 64 MiB for oversized requests. A quick survey of SATPI, DVBlast, dvbv5-zap, minisatip, TVheadend, MythTV, and MuMuDVB found the largest requested buffer to be about 30 MiB. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Fixes: a095be4b030c ("V4L/DVB (7659): dvb-core: Implement DMX_SET_BUFFER_SIZE for dvr") Cc: stable@vger.kernel.org Reported-by: AutonomousCodeSecurity@microsoft.com Link: https://lore.kernel.org/all/20260722193719.81157-1-blbllhy@gmail.com/ Signed-off-by: Cen Zhang (Microsoft) --- V3: - Clamp oversized requests to maximum instead of returning -EINVAL. - Clamp before size comparison to avoid redundant reallocation. - Explain the choice of the 64 MiB limit. V2: - Add Cc: stable and Link: tag. drivers/media/dvb-core/dmxdev.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/drivers/media/dvb-core/dmxdev.c b/drivers/media/dvb-core/dmxdev.c index 3c8bc75e4d6c..330255312c85 100644 --- a/drivers/media/dvb-core/dmxdev.c +++ b/drivers/media/dvb-core/dmxdev.c @@ -20,6 +20,9 @@ #include #include +/* 64 MiB upper bound for DVB ring buffer allocations */ +#define DVB_BUFFER_SIZE_MAX (64 * 1024 * 1024) + static int debug; module_param(debug, int, 0644); @@ -288,6 +291,8 @@ static int dvb_dvr_set_buffer_size(struct dmxdev *dmxdev, dprintk("%s\n", __func__); + if (size > DVB_BUFFER_SIZE_MAX) + size = DVB_BUFFER_SIZE_MAX; if (buf->size == size) return 0; if (!size) @@ -327,6 +332,8 @@ static int dvb_dmxdev_set_buffer_size(struct dmxdev_filter *dmxdevfilter, void *newmem; void *oldmem; + if (size > DVB_BUFFER_SIZE_MAX) + size = DVB_BUFFER_SIZE_MAX; if (buf->size == size) return 0; if (!size) -- 2.52.0