Hi Jyoti,
Please find my responses inline below.
On 2026/10/01 05:29 PM, Jyoti Gupta wrote:
> On 2026-10-01 00:20, Amit Machhiwal wrote:
> > On 2026/09/30 11:39 PM, Jyoti Gupta wrote:
> > > mpic_alloc() allocates struct mpic (and optionally the protected
> > > sources bitmap) but does not free them when mpic_setup_error_int() or
> > > irq_domain_create_linear() fails, leaking the memory.
> > >
> > > Free the bitmap and the mpic in the common error path before
> > > dropping the
> > > device node reference.
> > >
> > > Fixes: 996983b75ceb ("powerpc/mpic: Search for open-pic device-tree
> > > node if NULL")
> > > Signed-off-by: Jyoti Gupta <[email protected]>
> > > ---
> > > arch/powerpc/sysdev/mpic.c | 11 +++++------
> > > 1 file changed, 5 insertions(+), 6 deletions(-)
> >
> > Thanks for addressing the comments from v1.
> >
> > A couple of minor suggestions:
> >
> > 1. Changelog & Links: It is always a good practice to include a
> > changelog below
> > the "---" line detailing the changes made in this version (e.g. "v1
> > -> v2:
> > ...") along with a link to the previous version(s) on
> > lore.kernel.org. This
> > helps reviewers and maintainers quickly track the evolution of the
> > patch.
> >
>
> Got it, thank you for the suggestion. I'll keep it in mind.
>
> > 2. Minor nit in cleanup logic below:
> >
> > >
> > > diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
> > > index 257886ec3f70..b21a880777cc 100644
> > > --- a/arch/powerpc/sysdev/mpic.c
> > > +++ b/arch/powerpc/sysdev/mpic.c
> > > @@ -1389,7 +1389,7 @@ struct mpic * __init mpic_alloc(struct
> > > device_node *node,
> > > if (fsl_version >= 0x401) {
> > > ret = mpic_setup_error_int(mpic, intvec_top - 13);
> > > if (ret)
> > > - return NULL;
> > > + goto err_of_node_put;
> > > }
> > >
> > > }
> > > @@ -1488,12 +1488,8 @@ struct mpic * __init mpic_alloc(struct
> > > device_node *node,
> > > intvec_top,
> > > &mpic_host_ops, mpic);
> > >
> > > - /*
> > > - * FIXME: The code leaks the MPIC object and mappings here; this
> > > - * is very unlikely to fail but it ought to be fixed anyways.
> > > - */
> > > if (mpic->irqhost == NULL)
> > > - return NULL;
> > > + goto err_of_node_put;
> > >
> > > /* Display version */
> > > switch (greg_feature & MPIC_GREG_FEATURE_VERSION_MASK) {
> > > @@ -1527,6 +1523,9 @@ struct mpic * __init mpic_alloc(struct
> > > device_node *node,
> > > return mpic;
> > >
> > > err_of_node_put:
> > > + if (mpic)
> > > + bitmap_free(mpic->protected);
> > > + kfree(mpic);
> >
> > Both bitmap_free() and kfree() safely handle NULL pointers (and mpic is
> > guaranteed to be non-NULL at this label anyway), so the 'if (mpic)'
> > check is
> > redundant.
> >
>
> Thanks for the review.
>
> Regarding the 'if (mpic)' check, I think we may need to keep it. While
> bitmap_free() and kfree() both safely handle NULL, the concern here is
> dereferencing mpic to obtain mpic->protected. There are two paths that
> reach err_of_node_put before mpic is allocated (line 1276):
> of_address_to_resource() failure at line 1258 and kzalloc_obj() returning
> NULL at line 1278. In both cases, mpic->protected would dereference a
> NULL/garbage pointer and crash.
Good catch on the early error paths before mpic allocation!
However, in v2, 'struct mpic *mpic' is left uninitialized at function entry
(since the '= NULL' initialization was dropped).
Looking more closely, if of_address_to_resource() fails at line 1258, control
jumps to err_of_node_put where 'mpic' contains uninitialized stack garbage. In
that case, 'if (mpic)' evaluates to true, leading to an invalid pointer
dereference when evaluating mpic->protected and a crash on kfree(mpic).
Rather than initializing mpic to NULL and checking 'if (mpic)' on error paths,
the preferred approach in Linux is to use layered error labels. In fact,
Documentation/process/coding-style.rst (Section 7, "Centralized exiting of
functions") specifically describes this pattern when discussing "one err bugs":
A common type of bug to be aware of is ``one err bugs`` which look like this:
.. code-block:: c
err:
kfree(foo->bar);
kfree(foo);
return ret;
The bug in this code is that on some exit paths ``foo`` is NULL. Normally the
fix for this is to split it up into two error labels ``err_free_bar:`` and
``err_free_foo:``:
.. code-block:: c
err_free_bar:
kfree(foo->bar);
err_free_foo:
kfree(foo);
return ret;
Applying that pattern here gives:
diff --git a/arch/powerpc/sysdev/mpic.c b/arch/powerpc/sysdev/mpic.c
index 257886ec3f70..d799cf4da7bd 100644
--- a/arch/powerpc/sysdev/mpic.c
+++ b/arch/powerpc/sysdev/mpic.c
@@ -1389,7 +1389,7 @@ struct mpic * __init mpic_alloc(struct device_node *node,
if (fsl_version >= 0x401) {
ret = mpic_setup_error_int(mpic, intvec_top - 13);
if (ret)
- return NULL;
+ goto err_free_mpic;
}
}
@@ -1488,12 +1488,8 @@ struct mpic * __init mpic_alloc(struct device_node *node,
intvec_top,
&mpic_host_ops, mpic);
- /*
- * FIXME: The code leaks the MPIC object and mappings here; this
- * is very unlikely to fail but it ought to be fixed anyways.
- */
if (mpic->irqhost == NULL)
- return NULL;
+ goto err_free_mpic;
/* Display version */
switch (greg_feature & MPIC_GREG_FEATURE_VERSION_MASK) {
@@ -1526,6 +1522,9 @@ struct mpic * __init mpic_alloc(struct device_node *node,
return mpic;
+err_free_mpic:
+ bitmap_free(mpic->protected);
+ kfree(mpic);
err_of_node_put:
of_node_put(node);
return NULL;
This ensures:
1. Early error paths (of_address_to_resource and kzalloc_obj failures) jump
directly to err_of_node_put without touching mpic.
2. Later error paths jump to err_free_mpic where mpic is guaranteed to be valid.
3. No 'if (mpic)' check or 'struct mpic *mpic = NULL;' is needed.
What do you think?
Thanks,
Amit
