media: atomisp: fix -Wdangling-pointer warning

ia_css_rmgr_acq_vbuf() uses a local on stack
"struct ia_css_rmgr_vbuf_handle v" variable.

When this path using this is hit, either the rmgr_pop_handle() call
will make *handle point to another vbuf-handle, or because
v.count == 0, ia_css_rmgr_refcount_retain_vbuf() will alloc a new
vbuf-handle and make *handle point to it.

So on leaving the function *handle will never point to the on stack
vbuf-handle, but gcc does not know this and emits the following:

drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c: In function ‘ia_css_rmgr_acq_vbuf’:
drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c:276:33: warning: storing the address of local variable ‘h’ in ‘*handle’ [-Wdangling-pointer=]
  276 |                         *handle = &h;
      |                         ~~~~~~~~^~~~
drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c:257:40: note: ‘h’ declared here
  257 |         struct ia_css_rmgr_vbuf_handle h;
      |                                        ^
drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c:257:40: note: ‘handle’ declared here

Rework the code using a new_handle helper to suppress this
false-postive compiler warning.

Link: https://lore.kernel.org/linux-media/20220612160556.108264-4-hdegoede@redhat.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

diff --git a/drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c b/drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c
index 1db28f8..2e07dab 100644 (file)
--- a/drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c
+++ b/drivers/staging/media/atomisp/pci/runtime/rmgr/src/rmgr_vbuf.c
@@ -254,14 +254,15 @@ void rmgr_pop_handle(struct ia_css_rmgr_vbuf_pool *pool,
 void ia_css_rmgr_acq_vbuf(struct ia_css_rmgr_vbuf_pool *pool,
                          struct ia_css_rmgr_vbuf_handle **handle)
 {
-       struct ia_css_rmgr_vbuf_handle h = { 0 };
-
        if ((!pool) || (!handle) || (!*handle)) {
                IA_CSS_LOG("Invalid inputs");
                return;
        }
 
        if (pool->copy_on_write) {
+               struct ia_css_rmgr_vbuf_handle *new_handle;
+               struct ia_css_rmgr_vbuf_handle h = { 0 };
+
                /* only one reference, reuse (no new retain) */
                if ((*handle)->count == 1)
                        return;
@@ -272,22 +273,29 @@ void ia_css_rmgr_acq_vbuf(struct ia_css_rmgr_vbuf_pool *pool,
                        h.size = (*handle)->size;
                        /* release ref to current buffer */
                        ia_css_rmgr_refcount_release_vbuf(handle);
-                       *handle = &h;
+                       new_handle = &h;
+               } else {
+                       new_handle = *handle;
                }
                /* get new buffer for needed size */
-               if ((*handle)->vptr == 0x0) {
+               if (new_handle->vptr == 0x0) {
                        if (pool->recycle) {
                                /* try and pop from pool */
-                               rmgr_pop_handle(pool, handle);
+                               rmgr_pop_handle(pool, &new_handle);
                        }
-                       if ((*handle)->vptr == 0x0) {
+                       if (new_handle->vptr == 0x0) {
                                /* we need to allocate */
-                               (*handle)->vptr = hmm_alloc((*handle)->size);
+                               new_handle->vptr = hmm_alloc(new_handle->size);
                        } else {
                                /* we popped a buffer */
+                               *handle = new_handle;
                                return;
                        }
                }
+               /* Note that new_handle will change to an internally maintained one */
+               ia_css_rmgr_refcount_retain_vbuf(&new_handle);
+               *handle = new_handle;
+               return;
        }
        /* Note that handle will change to an internally maintained one */
        ia_css_rmgr_refcount_retain_vbuf(handle);