media: v4l2-event: Annotate struct v4l2_subscribed_event with __counted_by

Prepare for the coming implementation by GCC and Clang of the __counted_by
attribute. Flexible array members annotated with __counted_by can have
their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
(for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
functions).

As found with Coccinelle[1], add __counted_by for
struct v4l2_subscribed_event.
Additionally, since the element count member must be set before accessing
the annotated flexible array member, move its initialization earlier.

[1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci

Cc: lijian <lijian@yulong.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>

diff --git a/drivers/media/v4l2-core/v4l2-event.c b/drivers/media/v4l2-core/v4l2-event.c
index c5ce9f11ad7bcece86f98be2a6c88f76c200d79e..3898ff7edddbf74d2650e5567d3f7b7d1c93552f 100644 (file)
--- a/drivers/media/v4l2-core/v4l2-event.c
+++ b/drivers/media/v4l2-core/v4l2-event.c
@@ -238,6 +238,7 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
        sev = kvzalloc(struct_size(sev, events, elems), GFP_KERNEL);
        if (!sev)
                return -ENOMEM;
+       sev->elems = elems;
        for (i = 0; i < elems; i++)
                sev->events[i].sev = sev;
        sev->type = sub->type;
@@ -245,7 +246,6 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
        sev->flags = sub->flags;
        sev->fh = fh;
        sev->ops = ops;
-       sev->elems = elems;
 
        mutex_lock(&fh->subscribe_lock);
 

diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h
index 4ffa914ade3a16b18bd3572b3461a4e1632bc90e..3a0e2588361cf451b3dbfc63dfab99550d13cf6a 100644 (file)
--- a/include/media/v4l2-event.h
+++ b/include/media/v4l2-event.h
@@ -78,7 +78,7 @@ struct v4l2_subscribed_event {
        unsigned int            elems;
        unsigned int            first;
        unsigned int            in_use;
-       struct v4l2_kevent      events[];
+       struct v4l2_kevent      events[] __counted_by(elems);
 };
 
 /**