From: Tomer Samara <tomersamara98@gmail.com>
To: Randy Dunlap <rdunlap@infradead.org>
Cc: "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Arve Hjønnevåg" <arve@android.com>,
"Riley Andrews" <riandrews@android.com>,
"Laura Abbott" <labbott@redhat.com>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Todd Kjos" <tkjos@android.com>,
"Martijn Coenen" <maco@android.com>,
"Joel Fernandes" <joel@joelfernandes.org>,
"Christian Brauner" <christian@brauner.io>,
"Hridya Valsaraju" <hridya@google.com>,
"Suren Baghdasaryan" <surenb@google.com>,
devel@driverdev.osuosl.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4 2/2] staging: android: Remove BUG from ion_system_heap.c
Date: Sat, 22 Aug 2020 12:34:21 +0300 [thread overview]
Message-ID: <20200822093421.GA6631@tsnow> (raw)
In-Reply-To: <3eba90dc-128f-49da-41a6-81494653d535@infradead.org>
On Fri, Aug 21, 2020 at 09:25:26AM -0700, Randy Dunlap wrote:
> On 8/21/20 8:28 AM, Tomer Samara wrote:
> > Remove BUG() from ion_sytem_heap.c
> >
> > this fix the following checkpatch issue:
> > Avoid crashing the kernel - try using WARN_ON &
> > recovery code ratherthan BUG() or BUG_ON().
> >
> > Signed-off-by: Tomer Samara <tomersamara98@gmail.com>
> > ---
> > drivers/staging/android/ion/ion_system_heap.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/staging/android/ion/ion_system_heap.c b/drivers/staging/android/ion/ion_system_heap.c
> > index eac0632ab4e8..00d6154aec34 100644
> > --- a/drivers/staging/android/ion/ion_system_heap.c
> > +++ b/drivers/staging/android/ion/ion_system_heap.c
> > @@ -30,7 +30,7 @@ static int order_to_index(unsigned int order)
> > for (i = 0; i < NUM_ORDERS; i++)
> > if (order == orders[i])
> > return i;
> > - BUG();
> > + /* This is impossible. */
> > return -1;
> > }
>
> Hi,
> Please explain why this is impossible.
>
> If some caller calls order_to_index(5), it will return -1, yes?
>
> --
> ~Randy
>
As Dan Carpenter says here https://lkml.kernel.org/lkml/cover.1597865771.git.tomersamara98@gmail.com/T/#mc790b91029565b1bb0cb87997b39007d9edb6e04.
After looking at callers we see that order_to_index called from 2 functions:
- alloc_buffer_page called from alloc_largest_available which
loop over all legit order nubmers
( Flow:
alloc_largest_available-->alloc_buffer_page-->order_to_index
)
- free_buffer_page takes the order using compound_order, which return 0 or
the order number for the page, this function has 2 callers too,
ion_system_heap_allocate (which called it in case of failure at sg_alloc_table,
thus calling from this flow will no casue error) and ion_system_heap_free
(which will be called on every sg table in the buffer that allocated good,
meaning from this flow also error will not be created).
( Flows:
ion_system_heap_free --> free_buffer_page --> order_to_index
ion_system_heap_allocate --> free_buffer_page --> order_to_index
)
Of course if some user will use this function with wrong order number he will be able to get this -1.
So should I remove this comment and resotre the error checks?
Btw, this is the same reason that I dropped the error check at ion_page_pool_shrink, so should I restore here also?
Thanks,
Tomer Samara
next prev parent reply other threads:[~2020-08-22 9:34 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 15:27 [PATCH v4 0/2] staging: android: Remove BUG/BUG_ON from ion Tomer Samara
2020-08-21 15:27 ` [PATCH v4 1/2] staging: android: Remove BUG_ON from ion_page_pool.c Tomer Samara
2020-08-24 11:22 ` Dan Carpenter
2020-08-21 15:28 ` [PATCH v4 2/2] staging: android: Remove BUG from ion_system_heap.c Tomer Samara
2020-08-21 16:25 ` Randy Dunlap
2020-08-22 9:34 ` Tomer Samara [this message]
2020-08-22 14:22 ` Randy Dunlap
2020-08-24 11:24 ` Dan Carpenter
2020-08-24 11:27 ` Dan Carpenter
2020-08-24 11:43 ` Dan Carpenter
2020-08-25 6:47 ` [PATCH v4 0/2] staging: android: Remove BUG/BUG_ON from ion Christoph Hellwig
2020-08-25 6:52 ` Greg Kroah-Hartman
2020-08-27 7:16 ` Christoph Hellwig
2020-08-27 12:15 ` Greg Kroah-Hartman
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