Hi!
On Thu, 22 Apr 2021 21:37:42 +0530
Atul Gopinathan <atulgopinathan@xxxxxxxxx> wrote:
> During probing phase of a gspca driver in "gspca_dev_probe2()", the
> stv06xx subdrivers have certain sensor variants (namely, hdcs_1x00,
> hdcs_1020 and pb_0100) that allocate memory for their respective
> sensor which is passed to the "sd->sensor_priv" field. During the
> same probe routine, after "sensor_priv" allocation, there are chances
> of later functions invoked to fail which result in the probing
> routine to end immediately via "goto out" path. While doing so, the
> memory allocated earlier for the sensor isn't taken care of resulting
> in memory leak.
>
> Fix this by adding operations to the gspca, stv06xx and down to the
> sensor levels to free this allocated memory during gspca probe
> failure.
>
> -
> The current level of hierarchy looks something like this:
>
> gspca (main driver) represented by struct gspca_dev
> |
> ___________|_____________________________________
> | | | | | | (subdrivers)
> | represented
> stv06xx by "struct
> sd" |
> _______________|_______________
> | | | | | (sensors)
> | |
> hdcs_1x00/1020 pb01000
> |_________________|
> |
> These three sensor variants
> allocate memory for
> "sd->sensor_priv" field.
>
> Here, "struct gspca_dev" is the representation used in the top level.
> In the sub-driver levels, "gspca_dev" pointer is cast to "struct sd*",
> something like this:
>
> struct sd *sd = (struct sd *)gspca_dev;
>
> This is possible because the first field of "struct sd" is
> "gspca_dev":
>
> struct sd {
> struct gspca_dev;
> .
> .
> }
>
> Therefore, to deallocate the "sd->sensor_priv" fields from
> "gspca_dev_probe2()" which is at the top level, the patch creates
> operations for the subdrivers and sensors to be invoked from the gspca
> driver levels. These operations essentially free the "sd->sensor_priv"
> which were allocated by the "config" and "init_controls" operations in
> the case of stv06xx sub-drivers and the sensor levels.
>
> This patch doesn't affect other sub-drivers or even sensors who never
> allocate memory to "sensor_priv". It has also been tested by syzbot
> and it returned an "OK" result.
>
> https://syzkaller.appspot.com/bug?id=ab69427f2911374e5f0b347d0d7795bfe384016c
> -
>
> Fixes: 4c98834addfe ("V4L/DVB (10048): gspca - stv06xx: New
> subdriver.") Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> Reported-by: syzbot+990626a4ef6f043ed4cd@xxxxxxxxxxxxxxxxxxxxxxxxx
> Tested-by: syzbot+990626a4ef6f043ed4cd@xxxxxxxxxxxxxxxxxxxxxxxxx
> Signed-off-by: Atul Gopinathan <atulgopinathan@xxxxxxxxx>
AFAIK, something similar is already applied to linux-media tree
https://git.linuxtv.org/media_tree.git/commit/?id=4f4e6644cd876c844cdb3bea2dd7051787d5ae25
--
With regards,
Pavel Skripkin
