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Message-ID: <CAAObsKBuaKtMDKuuwtYLALxx6tx82ioxbfncnVMrXVgB7dptHA@mail.gmail.com> Date: Wed, 24 Apr 2019 07:34:06 +0200 From: Tomeu Vizoso <tomeu.vizoso@...labora.com> To: Enric Balletbo i Serra <enric.balletbo@...labora.com> Cc: open list <linux-kernel@...r.kernel.org>, Alyssa Rosenzweig <alyssa@...enzweig.io>, MyungJoo Ham <myungjoo.ham@...sung.com>, Kyungmin Park <kyungmin.park@...sung.com>, Chanwoo Choi <cw00.choi@...sung.com>, linux-pm@...r.kernel.org Subject: Re: [PATCH] PM / devfreq: Return -ENODEV from try_then_request_governor On Tue, 23 Apr 2019 at 11:56, Enric Balletbo i Serra <enric.balletbo@...labora.com> wrote: > > Hi Tomeu, > > On 23/4/19 10:11, Tomeu Vizoso wrote: > > Callers don't expect it to return NULL, but an error code. > > > > Fixes Oops such as the one below, when one tries to set a governor that > > isn't available: > > > > Unable to handle kernel NULL pointer dereference at virtual address 00000018 > > > > [<c0dcf718>] (governor_store) from [<c0539558>] (kernfs_fop_write+0x100/0x1e0) > > [<c0539558>] (kernfs_fop_write) from [<c04b09b4>] (__vfs_write+0x2c/0x17c) > > [<c04b09b4>] (__vfs_write) from [<c04b33fc>] (vfs_write+0xa4/0x184) > > [<c04b33fc>] (vfs_write) from [<c04b361c>] (ksys_write+0x4c/0xac) > > [<c04b361c>] (ksys_write) from [<c0301000>] (ret_fast_syscall+0x0/0x28) > > > > Signed-off-by: Tomeu Vizoso <tomeu.vizoso@...labora.com> > > Fixes: 23c7b54ca1cd ("PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.") > > Reported-by: Alyssa Rosenzweig <alyssa@...enzweig.io> > > Cc: Enric Balletbo i Serra <enric.balletbo@...labora.com> > > --- > > There is already a fix for that. The fix was initially sent in October [2] but > unfortunately it got lost. I resend and now is queued [1]. Hopefully the Fixes > tag will help to pick the fix to the proper kernel releases. Actually, Steve Price sent a third patch for this same issue. Glad to read that it's being merged. Thanks, Tomeu > Thanks, > Enric > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git/mzx/devfreq.git/commit/?h=for-next&id=b53b0128052ffd687797d5f4deeb76327e7b5711 > > [2] https://lkml.org/lkml/2018/10/16/744 > > > drivers/devfreq/devfreq.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c > > index 0ae3de76833b..5539e9be718d 100644 > > --- a/drivers/devfreq/devfreq.c > > +++ b/drivers/devfreq/devfreq.c > > @@ -254,7 +254,7 @@ static struct devfreq_governor *try_then_request_governor(const char *name) > > /* Restore previous state before return */ > > mutex_lock(&devfreq_list_lock); > > if (err) > > - return NULL; > > + return ERR_PTR(-ENODEV); > > > > governor = find_devfreq_governor(name); > > } > >
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