Re: [PATCH] nvmem: core: add a missing of_node_put

[Christophe JAILLET]

Le 23/04/2021 à 11:30, Srinivas Kandagatla a écrit :
> On 20/04/2021 21:12, Christophe JAILLET wrote:
> > 'for_each_child_of_node' performs an of_node_get on each iteration, so a
> > return from the middle of the loop requires an of_node_put.
> >
> > Fixes: e888d445ac33 ("nvmem: resolve cells from DT at registration time")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> > ---
> >   drivers/nvmem/core.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c
> > index bca671ff4e54..4375e52ba6c2 100644
> > --- a/drivers/nvmem/core.c
> > +++ b/drivers/nvmem/core.c
> > @@ -686,12 +686,15 @@ static int nvmem_add_cells_from_of(struct 
> > nvmem_device *nvmem)
> >               continue;
> >           if (len < 2 * sizeof(u32)) {
> >               dev_err(dev, "nvmem: invalid reg on %pOF\n", child);
> > +            of_node_put(child);
> >               return -EINVAL;
> >           }
> >           cell = kzalloc(sizeof(*cell), GFP_KERNEL);
> > -        if (!cell)
> > +        if (!cell) {
> > +            of_node_put(child);
> >               return -ENOMEM;
> > +        }
> >           cell->nvmem = nvmem;
> >           cell->np = of_node_get(child);
> > @@ -717,6 +720,7 @@ static int nvmem_add_cells_from_of(struct 
> > nvmem_device *nvmem)
> >               kfree_const(cell->name);
> >               of_node_put(cell->np);
> >               kfree(cell);
> > +            of_node_put(child);
>
> two of_node_put looks bit confusing to the reader, can you move the
>
> cell->np = of_node_get(child); just before nvmem_cell_add(cell);
> so that we can remove extra put.

Sure.
I didn't pay attention that cell->np and child were the same and that 
the code looked odd now.

Thx for the review and the comment.


> Was this reported by some kind of static analysis tool?
>

Yes, this was found by coccinelle.
The script used was an old one posted by Julia Lawall a few years ago:

// <smpl>
@r@
local idexpression n;
expression e1,e2;
iterator name for_each_node_by_name, for_each_node_by_type,
for_each_compatible_node, for_each_matching_node,
for_each_matching_node_and_match, for_each_child_of_node,
for_each_available_child_of_node, for_each_node_with_property;
iterator i;
statement S;
expression list [n1] es;
@@

(
(
for_each_node_by_name(n,e1) S
|
for_each_node_by_type(n,e1) S
|
for_each_compatible_node(n,e1,e2) S
|
for_each_matching_node(n,e1) S
|
for_each_matching_node_and_match(n,e1,e2) S
|
for_each_child_of_node(e1,n) S
|
for_each_available_child_of_node(e1,n) S
|
for_each_node_with_property(n,e1) S
)
&
i(es,n,...) S
)

@@
local idexpression r.n;
iterator r.i;
expression e;
expression list [r.n1] es;
@@

 i(es,n,...) {
   ...
(
   of_node_put(n);
|
   e = n
|
   return n;
|
+  of_node_put(n);
?  return ...;
)
   ...
 }

@@
local idexpression r.n;
iterator r.i;
expression e;
expression list [r.n1] es;
@@

 i(es,n,...) {
   ...
(
   of_node_put(n);
|
   e = n
|
+  of_node_put(n);
?  break;
)
   ...
 }
... when != n

@@
local idexpression r.n;
iterator r.i;
expression e;
identifier l;
expression list [r.n1] es;
@@

 i(es,n,...) {
   ...
(
   of_node_put(n);
|
   e = n
|
+  of_node_put(n);
?  goto l;
)
   ...
 }
...
l: ... when != n
// </smpl>


> --srini
>
>
>
> >               return -EINVAL;
> >           }