From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Schmid, Carsten" <Carsten_Schmid@mentor.com>
Cc: "bp@suse.de" <bp@suse.de>,
"dan.j.williams@intel.com" <dan.j.williams@intel.com>,
"mingo@kernel.org" <mingo@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"osalvador@suse.de" <osalvador@suse.de>,
"rdunlap@infradead.org" <rdunlap@infradead.org>,
"richardw.yang@linux.intel.com" <richardw.yang@linux.intel.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>
Subject: Re: Resend [PATCH] kernel/resource.c: invalidate parent when freed resource has childs
Date: Fri, 9 Aug 2019 13:09:58 -0700 [thread overview]
Message-ID: <CAHk-=wi=3y4XW1RA15crZpbDy8Z0pgQL7nHeTn69MX1xm3J4yw@mail.gmail.com> (raw)
In-Reply-To: <1565358624103.3694@mentor.com>
On Fri, Aug 9, 2019 at 6:50 AM Schmid, Carsten
<Carsten_Schmid@mentor.com> wrote:
>
> @@ -1200,6 +1200,15 @@ void __release_region(struct resource *parent, resource_size_t start,
> write_unlock(&resource_lock);
> if (res->flags & IORESOURCE_MUXED)
> wake_up(&muxed_resource_wait);
> +
> + write_lock(&resource_lock);
> + if (res->child) {
> + printk(KERN_WARNING "__release_region: %s has child %s,"
> + "invalidating childs parent\n",
> + res->name, res->child->name);
> + res->child->parent = NULL;
> + }
> + write_unlock(&resource_lock);
> free_resource(res);
So I think that this should be inside the previous resource_lock, and
before the whole "wake up muxed resource".
Also, a few other issues:
- what about other freeing cases? I'm looking at
release_mem_region_adjustable()
which has the same pattern where a resource may be freed.
- what about multiple children? Your patch sets res->child->parent to
NULL, but what about possible other children (iow, the
res->child->sibling list)
- releasing a resource without having released its children is a
nasty bug, but the bug is now here in release_region, it is in the
*caller*. The printk() (or pr_warn()) doesn't really help find that.
So my gut feel is that this patch is a symptom of a real bug, and a
warning is worthwhile to fix that bug, but more thought is needed.
Maybe something more along the line of
diff --git a/kernel/resource.c b/kernel/resource.c
index 7ea4306503c5..ebe06d77b06a 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -1211,6 +1211,8 @@ void __release_region(struct resource
*parent, resource_size_t start,
}
if (res->start != start || res->end != end)
break;
+ if (WARN_ON_ONCE(res->child))
+ break;
*p = res->sibling;
write_unlock(&resource_lock);
if (res->flags & IORESOURCE_MUXED)
would be more appropriate? It simply refuses to free a resource that
has children, and gives a warning (with a backtrace) for the situation
(since clearly we now end up with a resource leak).
Linus
next prev parent reply other threads:[~2019-08-09 20:10 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-08 15:40 [PATCH] kernel/resource.c: invalidate parent when freed resource has childs Schmid, Carsten
2019-08-09 13:50 ` Resend " Schmid, Carsten
2019-08-09 16:59 ` Dan Williams
2019-08-09 18:37 ` Joe Perches
2019-08-09 18:54 ` [PATCH] kernel/resource.c: Convert printks to pr_<level> Joe Perches
2019-08-09 20:09 ` Linus Torvalds [this message]
2019-08-09 22:38 ` Resend [PATCH] kernel/resource.c: invalidate parent when freed resource has childs Wei Yang
2019-08-09 22:45 ` Linus Torvalds
2019-08-10 0:44 ` Wei Yang
2019-08-12 8:39 ` AW: " Schmid, Carsten
2019-08-13 8:09 ` Schmid, Carsten
2019-08-14 14:48 ` [PATCH v2] " Schmid, Carsten
2019-08-14 16:29 ` Wei Yang
2019-08-15 8:18 ` AW: " Schmid, Carsten
2019-08-15 13:03 ` Wei Yang
2019-08-15 13:17 ` AW: " Schmid, Carsten
2019-08-16 10:18 ` [PATCH] kernel/resource.c: warn if released region has children Schmid, Carsten
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