From: "Rafael J. Wysocki" <rafael@kernel.org>
To: Dan Williams <dan.j.williams@intel.com>
Cc: gregkh@linuxfoundation.org,
Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>,
Marc Herbert <marc.herbert@intel.com>,
"Rafael J. Wysocki" <rafael@kernel.org>,
linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org,
linux-coco@lists.linux.dev, alsa-devel@alsa-project.org
Subject: Re: [PATCH 1/3] sysfs: Fix crash on empty group attributes array
Date: Thu, 22 Feb 2024 22:14:55 +0100 [thread overview]
Message-ID: <CAJZ5v0hmD+7iSKKexpUccvMUtjNpd9fHo3vRrshD_s=rb5Vq_w@mail.gmail.com> (raw)
In-Reply-To: <170863445442.1479840.1818801787239831650.stgit@dwillia2-xfh.jf.intel.com>
On Thu, Feb 22, 2024 at 9:40 PM Dan Williams <dan.j.williams@intel.com> wrote:
>
> It turns out that arch/x86/events/intel/core.c makes use of "empty"
> attributes.
>
> static struct attribute *empty_attrs;
>
> __init int intel_pmu_init(void)
> {
> struct attribute **extra_skl_attr = &empty_attrs;
> struct attribute **extra_attr = &empty_attrs;
> struct attribute **td_attr = &empty_attrs;
> struct attribute **mem_attr = &empty_attrs;
> struct attribute **tsx_attr = &empty_attrs;
> ...
>
> That breaks the assumption __first_visible() that expects that if
> grp->attrs is set then grp->attrs[0] must also be set and results in
> backtraces like:
>
> BUG: kernel NULL pointer dereference, address: 00rnel mode
> #PF: error_code(0x0000) - not-present ] PREEMPT SMP NOPTI
> CPU: 1 PID: 1 Comm: swapper/IP: 0010:exra_is_visible+0x14/0x20
> ? exc_page_fault+0x68/0x190
> internal_create_groups+0x42/0xa0
> pmu_dev_alloc+0xc0/0xe0
> perf_event_sysfs_init+0x580000000000 ]---
> RIP: 0010:exra_is_visible+0x14/0
>
> Check for non-empty attributes array before calling is_visible().
>
> Reported-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> Closes: https://github.com/thesofproject/linux/pull/4799#issuecomment-1958537212
> Fixes: 70317fd24b41 ("sysfs: Introduce a mechanism to hide static attribute_groups")
This is not in the mainline, so linux-next I suppose?
> Cc: Marc Herbert <marc.herbert@intel.com>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> fs/sysfs/group.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/sysfs/group.c b/fs/sysfs/group.c
> index ccb275cdabcb..8c63ba3cfc47 100644
> --- a/fs/sysfs/group.c
> +++ b/fs/sysfs/group.c
> @@ -33,10 +33,10 @@ static void remove_files(struct kernfs_node *parent,
>
> static umode_t __first_visible(const struct attribute_group *grp, struct kobject *kobj)
> {
> - if (grp->attrs && grp->is_visible)
> + if (grp->attrs && grp->attrs[0] && grp->is_visible)
> return grp->is_visible(kobj, grp->attrs[0], 0);
>
> - if (grp->bin_attrs && grp->is_bin_visible)
> + if (grp->bin_attrs && grp->bin_attrs[0] && grp->is_bin_visible)
> return grp->is_bin_visible(kobj, grp->bin_attrs[0], 0);
>
> return 0;
>
next prev parent reply other threads:[~2024-02-22 21:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-22 20:40 [PATCH 0/3] sysfs: Group visibility fixups Dan Williams
2024-02-22 20:40 ` [PATCH 1/3] sysfs: Fix crash on empty group attributes array Dan Williams
2024-02-22 21:14 ` Rafael J. Wysocki [this message]
2024-02-22 22:03 ` Dan Williams
2024-02-22 23:15 ` Dan Williams
2024-04-22 9:20 ` Lukas Wunner
2024-04-26 17:59 ` Dan Williams
2024-04-26 19:18 ` Lukas Wunner
2024-04-27 11:05 ` Greg KH
2024-04-27 16:49 ` Dan Williams
2024-04-27 21:14 ` Lukas Wunner
2024-04-27 21:33 ` Dan Williams
2024-04-27 22:39 ` Dan Williams
2024-04-27 23:09 ` Dan Williams
2024-04-28 10:08 ` Lukas Wunner
2024-04-29 17:47 ` Dan Williams
2024-02-22 20:41 ` [PATCH 2/3] sysfs: Document new "group visible" helpers Dan Williams
2024-02-22 20:41 ` [PATCH 3/3] sysfs: Introduce DEFINE_SIMPLE_SYSFS_GROUP_VISIBLE() Dan Williams
2024-02-23 6:33 ` [PATCH 0/3] sysfs: Group visibility fixups Greg KH
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