From: Pedro Falcato <pfalcato@suse.de>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Josh Law <hlcj1234567@gmail.com>,
"Liam R . Howlett" <Liam.Howlett@oracle.com>,
Alice Ryhl <aliceryhl@google.com>,
Andrew Ballance <andrewjballance@gmail.com>,
Josh Law <objecting@objecting.org>,
maple-tree@lists.infradead.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] lib/maple_tree: fix potential NULL dereference in mas_pop_node()
Date: Thu, 12 Mar 2026 23:22:45 +0000 [thread overview]
Message-ID: <i6tmfotangjjtzek5txtvoiav3xrfvwtw6cppooyja5mvywmz6@2c5rnyxqpgu6> (raw)
In-Reply-To: <20260312134531.49c1f9171b4b0bc8352e678d@linux-foundation.org>
On Thu, Mar 12, 2026 at 01:45:31PM -0700, Andrew Morton wrote:
> On Thu, 12 Mar 2026 18:40:53 +0000 Josh Law <hlcj1234567@gmail.com> wrote:
>
> > If kmem_cache_alloc_from_sheaf() returns NULL (possible under
> > GFP_NOWAIT pressure), mas_pop_node() falls through to the out label
> > and dereferences the NULL pointer in memset(ret, 0, sizeof(*ret)).
>
> This is such a glaring bug that I wonder if we're missing something.
According to my local copy of lib/maple_tree.c:
mas_pop_node() - Get a previously allocated maple node from the maple state.
Note the "previously" :) kmem_cache_alloc_from_sheaf() can only fail if you
run out of objects in the sheaf.
So yeah, this "bug" looks bogus.
--
Pedro
next prev parent reply other threads:[~2026-03-12 23:22 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-12 18:40 Josh Law
2026-03-12 18:40 ` [PATCH 2/3] lib/maple_tree: fix always-true condition in mas_erase() Josh Law
2026-04-01 3:24 ` Liam R. Howlett
2026-03-12 20:45 ` [PATCH 1/3] lib/maple_tree: fix potential NULL dereference in mas_pop_node() Andrew Morton
2026-03-12 20:49 ` Josh Law
2026-03-12 20:56 ` Josh Law
2026-03-12 21:14 ` Josh Law
2026-03-12 23:00 ` Alice Ryhl
2026-03-12 23:22 ` Pedro Falcato [this message]
2026-03-13 7:17 ` Josh Law
2026-03-13 9:05 ` Pedro Falcato
2026-03-13 16:11 ` Josh Law
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