On Tue, May 08, 2018 at 08:04:54AM -0500, Wenwen Wang wrote: > On Tue, May 8, 2018 at 7:16 AM, Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote: > > On Wed, May 02, 2018 at 05:38:49PM -0500, Wenwen Wang wrote: > >> At the end of atomisp_subdev_set_selection(), the function > >> atomisp_subdev_get_rect() is invoked to get the pointer to v4l2_rect. Since > >> this function may return a NULL pointer, it is firstly invoked to check > >> the returned pointer. If the returned pointer is not NULL, then the > >> function is invoked again to obtain the pointer and the memory content > >> at the location of the returned pointer is copied to the memory location of > >> r. In most cases, the pointers returned by the two invocations are same. > >> However, given that the pointer returned by the function > >> atomisp_subdev_get_rect() is not a constant, it is possible that the two > >> invocations return two different pointers. For example, another thread may > >> race to modify the related pointers during the two invocations. > > > > You're assuming a very serious race condition exists. > > > > > >> In that > >> case, even if the first returned pointer is not null, the second returned > >> pointer might be null, which will cause issues such as null pointer > >> dereference. > > > > And then complaining that if a really serious bug exists then this very > > minor bug would exist too... If there were really a race condition like > > that then we'd want to fix it instead. In other words, this is not a > > real life bug fix. > > > > But it would be fine as a readability or static checker fix so that's > > fine. > > Thanks for your response. From the performance perspective, this bug > should also be fixed, as the second invocation is redundant if it is > expected to return a same pointer as the first one. The arguments are unchanged so the function returns the same pointer. Btw. this driver is being removed; please see discussion here: <URL:https://www.spinics.net/lists/linux-media/msg133223.html> -- Sakari Ailus sakari.ailus@xxxxxxxxxxxxxxx _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
