On Sun, 2 Jan 2011, Jesper Juhl wrote:
> On Fri, 31 Dec 2010, Malcolm Priestley wrote:
>
> > On Fri, 2010-12-31 at 15:51 +0100, Jesper Juhl wrote:
> > > On Fri, 31 Dec 2010, Malcolm Priestley wrote:
> > >
> > > > On Fri, 2010-12-31 at 00:11 +0100, Jesper Juhl wrote:
> > > > > Hi,
> > > > >
> > > > > We may leak the storage allocated to 'state' in
> > > > > drivers/media/dvb/frontends/ix2505v.c::ix2505v_attach() on error.
> > > > > This patch makes sure we free the allocated memory in the failure
> > > > > case.
> > > > >
> > > > >
> > > > > Signed-off-by: Jesper Juhl <j...@chaosbits.net>
> > > > > ---
> > > > > ix2505v.c | 1 +
> > > > > 1 file changed, 1 insertion(+)
> > > > >
> > > > > Compile tested only.
> > > > >
> > > > > diff --git a/drivers/media/dvb/frontends/ix2505v.c
> > > > > b/drivers/media/dvb/frontends/ix2505v.c
> > > > > index 55f2eba..fcb173d 100644
> > > > > --- a/drivers/media/dvb/frontends/ix2505v.c
> > > > > +++ b/drivers/media/dvb/frontends/ix2505v.c
> > > > > @@ -293,6 +293,7 @@ struct dvb_frontend *ix2505v_attach(struct
> > > > > dvb_frontend *fe,
> > > > > ret = ix2505v_read_status_reg(state);
> > > > >
> > > > > if (ret & 0x80) {
> > > > > + kfree(state);
> > > > > deb_i2c("%s: No IX2505V found\n", __func__);
> > > > > goto error;
> > > > > }
> > > > >
> > > > Memory is freed in...
> > > >
> > > > error:
> > > > ix2505v_release(fe);
> > > > return NULL;
> > > >
> > > > via...
> > > >
> > > > static int ix2505v_release(struct dvb_frontend *fe)
> > > > {
> > > > struct ix2505v_state *state = fe->tuner_priv;
> > > >
> > > > fe->tuner_priv = NULL;
> > > > kfree(state);
> > > >
> > > > return 0;
> > > > }
> > > >
> > >
> > > Except that 'state' has not been assigned to fe->tuner_priv at this
> > > point, so ix2505v_release() cannot free the memory that was just
> > > allocated with kzalloc().
> > >
> > >
> > > state is a local variable:
> > > struct ix2505v_state *state = NULL;
> > > ...
> > >
> > > we allocate memory and assign it to 'state' here:
> > > state = kzalloc(sizeof(struct ix2505v_state),
> > > GFP_KERNEL);
> > > if (NULL == state)
> > > return NULL;
> > >
> > > state->config = config;
> > > state->i2c = i2c;
> > >
> > > here 'state' is used, but not in a way that saves it anywhere:
> > > if (state->config->tuner_write_only) {
> > > if (fe->ops.i2c_gate_ctrl)
> > > fe->ops.i2c_gate_ctrl(fe, 1);
> > >
> > > this function call involves 'state' but it does not save it anywhere
> > > either:
> > > ret = ix2505v_read_status_reg(state);
> > >
> > > if (ret & 0x80) {
> > > deb_i2c("%s: No IX2505V found\n",
> > > __func__);
> > > so when we jump to error here 'state' still exists only as the local
> > > variable, it has not been assigned to anything else.
> > > goto error;
> > > }
> > > ...
> > > error:
> > > there is no way this function call can free 'state' on this path since
> > > it has not been assigned to fe->tuner_priv.
> > > ix2505v_release(fe);
> > > The local variable state goes out of scope here and leaks the memory it
> > > points to:
> > > return NULL;
> > > }
> > >
> > > Am I missing something?
> >
> > Oh, Sorry, I see it now.
> >
> > Now there is two options.
> >
> > Either;
> >
> > 1) Move fe->tuner_priv = state to below line 287, so it can be released
> > by ix2505v_release and fe->tuner_priv returned to NULL;
> >
> > 2) or not calling ix2505v_release changing line 314 to kfree(state).
> > fe->tuner_priv will remain NULL through out.
> >
> [...]
>
> How about this?
>
Or actually, I think this is better:
Signed-off-by: Jesper Juhl <j...@chaosbits.net>
---
ix2505v.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/media/dvb/frontends/ix2505v.c
b/drivers/media/dvb/frontends/ix2505v.c
index 55f2eba..846ffd3 100644
--- a/drivers/media/dvb/frontends/ix2505v.c
+++ b/drivers/media/dvb/frontends/ix2505v.c
@@ -311,7 +311,7 @@ struct dvb_frontend *ix2505v_attach(struct dvb_frontend *fe,
return fe;
error:
- ix2505v_release(fe);
+ kfree(state);
return NULL;
}
EXPORT_SYMBOL(ix2505v_attach);
--
Jesper Juhl <j...@chaosbits.net> http://www.chaosbits.net/
Don't top-post http://www.catb.org/~esr/jargon/html/T/top-post.html
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