From: Matthew Wilcox <willy@infradead.org>
To: "Sokolowski, Jan" <jan.sokolowski@intel.com>
Cc: "Christian König" <christian.koenig@amd.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>
Subject: Re: [RFC PATCH 1/1] idr: do not create idr if new id would be outside given range
Date: Fri, 28 Nov 2025 17:50:42 +0000 [thread overview]
Message-ID: <aSng8hKuttOWQuds@casper.infradead.org> (raw)
In-Reply-To: <IA4PR11MB92511BAEF257742C82ED590199DCA@IA4PR11MB9251.namprd11.prod.outlook.com>
On Fri, Nov 28, 2025 at 04:47:17PM +0000, Sokolowski, Jan wrote:
> > No. You didn't co-develop anything. You reported the bug, badly.
> >
> And I've sent a potential patch on how it should've been fixed. That should count for something, right?
Literally everything about that patch was wrong. If I'd used any of it,
you'd have a point, but the entire approach was wrong.
You _can't_allow the allocation to succeed and then undo it. There might
be an RCU-protected reader which would see the intermediate state.
And that's an inconsistency we guarantee can't happen; an RCU reader
can see the state before the lock, the state after the lock. It must
not see a state that never happened.
If you'd written a test case, I'd happily add a co-developed-by tag.
But you didn't do that either.
prev parent reply other threads:[~2025-11-28 17:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-27 9:27 [RFC PATCH 0/1] IDR fix for potential id mismatch Jan Sokolowski
2025-11-27 9:27 ` [RFC PATCH 1/1] idr: do not create idr if new id would be outside given range Jan Sokolowski
2025-11-27 13:38 ` Matthew Wilcox
2025-11-27 13:54 ` Matthew Wilcox
2025-11-27 14:03 ` Christian König
2025-11-27 14:11 ` Matthew Wilcox
2025-11-27 14:55 ` Matthew Wilcox
2025-11-27 15:02 ` Christian König
2025-11-28 9:03 ` Sokolowski, Jan
2025-11-28 15:52 ` Matthew Wilcox
2025-11-28 16:47 ` Sokolowski, Jan
2025-11-28 17:50 ` Matthew Wilcox [this message]
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