| Message ID | 20241021105028.19794-2-pstanner@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [1/2] drm/sched: memset() 'job' in drm_sched_job_init() | expand |
Am 21.10.24 um 12:50 schrieb Philipp Stanner: > drm_sched_job_init() has no control over how users allocate struct > drm_sched_job. Unfortunately, the function can also not set some struct > members such as job->sched. > > This could theoretically lead to UB by users dereferencing the struct's > pointer members too early. > > It is easier to debug such issues if these pointers are initialized to > NULL, so dereferencing them causes a NULL pointer exception. > Accordingly, drm_sched_entity_init() does precisely that and initializes > its struct with memset(). > > Initialize parameter "job" to 0 in drm_sched_job_init(). > > Signed-off-by: Philipp Stanner <pstanner@redhat.com> > --- > No changes in v2. > > +CC Christian and Tvrtko in this thread. > Would be cool if someone can do a review. > --- > drivers/gpu/drm/scheduler/sched_main.c | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c > index dab8cca79eb7..2e0e5a9577d1 100644 > --- a/drivers/gpu/drm/scheduler/sched_main.c > +++ b/drivers/gpu/drm/scheduler/sched_main.c > @@ -796,6 +796,14 @@ int drm_sched_job_init(struct drm_sched_job *job, > return -EINVAL; > } > > + /* > + * We don't know for sure how the user has allocated. Thus, zero the > + * struct so that unallowed (i.e., too early) usage of pointers that > + * this function does not set is guaranteed to lead to a NULL pointer > + * exception instead of UB. > + */ > + memset(job, 0, sizeof(*job)); > + Maybe just implicitly set the sched pointer to NULL here? On the other hand compilers these days are really good at optimizing that away anyway, so feel free to add Reviewed-by: Christian König <christian.koenig@amd.com> to the series as is as well. Regards, Christian. > job->entity = entity; > job->credits = credits; > job->s_fence = drm_sched_fence_alloc(entity, owner);
On Mon, 2024-10-21 at 15:05 +0200, Christian König wrote: > Am 21.10.24 um 12:50 schrieb Philipp Stanner: > > drm_sched_job_init() has no control over how users allocate struct > > drm_sched_job. Unfortunately, the function can also not set some > > struct > > members such as job->sched. > > > > This could theoretically lead to UB by users dereferencing the > > struct's > > pointer members too early. > > > > It is easier to debug such issues if these pointers are initialized > > to > > NULL, so dereferencing them causes a NULL pointer exception. > > Accordingly, drm_sched_entity_init() does precisely that and > > initializes > > its struct with memset(). > > > > Initialize parameter "job" to 0 in drm_sched_job_init(). > > > > Signed-off-by: Philipp Stanner <pstanner@redhat.com> > > --- > > No changes in v2. > > > > +CC Christian and Tvrtko in this thread. > > Would be cool if someone can do a review. > > --- > > drivers/gpu/drm/scheduler/sched_main.c | 8 ++++++++ > > 1 file changed, 8 insertions(+) > > > > diff --git a/drivers/gpu/drm/scheduler/sched_main.c > > b/drivers/gpu/drm/scheduler/sched_main.c > > index dab8cca79eb7..2e0e5a9577d1 100644 > > --- a/drivers/gpu/drm/scheduler/sched_main.c > > +++ b/drivers/gpu/drm/scheduler/sched_main.c > > @@ -796,6 +796,14 @@ int drm_sched_job_init(struct drm_sched_job > > *job, > > return -EINVAL; > > } > > > > + /* > > + * We don't know for sure how the user has allocated. > > Thus, zero the > > + * struct so that unallowed (i.e., too early) usage of > > pointers that > > + * this function does not set is guaranteed to lead to a > > NULL pointer > > + * exception instead of UB. > > + */ > > + memset(job, 0, sizeof(*job)); > > + > > Maybe just implicitly set the sched pointer to NULL here? > > On the other hand compilers these days are really good at optimizing > that away anyway, so feel free to add Reviewed-by: Christian König > <christian.koenig@amd.com> to the series as is as well. (I had performance-tested it with several million jobs and couldn't detect a performance regression that was measurable) Applied #1 to drm-misc-next, thanks. Regarding patch #2, I just noticed that it violates the docstring style. I therefore hereby reject my own patch and will resubmit it in a cleaner form ^^' P. > > Regards, > Christian. > > > job->entity = entity; > > job->credits = credits; > > job->s_fence = drm_sched_fence_alloc(entity, owner); >
diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c index dab8cca79eb7..2e0e5a9577d1 100644 --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -796,6 +796,14 @@ int drm_sched_job_init(struct drm_sched_job *job, return -EINVAL; } + /* + * We don't know for sure how the user has allocated. Thus, zero the + * struct so that unallowed (i.e., too early) usage of pointers that + * this function does not set is guaranteed to lead to a NULL pointer + * exception instead of UB. + */ + memset(job, 0, sizeof(*job)); + job->entity = entity; job->credits = credits; job->s_fence = drm_sched_fence_alloc(entity, owner);
drm_sched_job_init() has no control over how users allocate struct drm_sched_job. Unfortunately, the function can also not set some struct members such as job->sched. This could theoretically lead to UB by users dereferencing the struct's pointer members too early. It is easier to debug such issues if these pointers are initialized to NULL, so dereferencing them causes a NULL pointer exception. Accordingly, drm_sched_entity_init() does precisely that and initializes its struct with memset(). Initialize parameter "job" to 0 in drm_sched_job_init(). Signed-off-by: Philipp Stanner <pstanner@redhat.com> --- No changes in v2. +CC Christian and Tvrtko in this thread. Would be cool if someone can do a review. --- drivers/gpu/drm/scheduler/sched_main.c | 8 ++++++++ 1 file changed, 8 insertions(+)