From: Catalin Marinas <catalin.marinas@arm.com>
To: Breno Leitao <leitao@debian.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org, kuba@kernel.org, stable@kenrel.org,
kernel-team@meta.com
Subject: Re: [PATCH] mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock
Date: Mon, 4 Aug 2025 11:25:58 +0100 [thread overview]
Message-ID: <aJCKtmtus770t5LA@arm.com> (raw)
In-Reply-To: <20250731-kmemleak_lock-v1-1-728fd470198f@debian.org>
On Thu, Jul 31, 2025 at 02:57:18AM -0700, Breno Leitao wrote:
> When netpoll is enabled, calling pr_warn_once() while holding
> kmemleak_lock in mem_pool_alloc() can cause a deadlock due to lock
> inversion with the netconsole subsystem. This occurs because
> pr_warn_once() may trigger netpoll, which eventually leads to
> __alloc_skb() and back into kmemleak code, attempting to reacquire
> kmemleak_lock.
>
> This is the path for the deadlock.
>
> mem_pool_alloc()
> -> raw_spin_lock_irqsave(&kmemleak_lock, flags);
> -> pr_warn_once()
> -> netconsole subsystem
> -> netpoll
> -> __alloc_skb
> -> __create_object
> -> raw_spin_lock_irqsave(&kmemleak_lock, flags);
>
> Fix this by setting a flag and issuing the pr_warn_once() after
> kmemleak_lock is released.
>
> Reported-by: Jakub Kicinski <kuba@kernel.org>
> Fixes: c5665868183fec ("mm: kmemleak: use the memory pool for early allocations")
> Signed-off-by: Breno Leitao <leitao@debian.org>
I think Andrew already added this to mm-stable but, for the record:
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
prev parent reply other threads:[~2025-08-04 10:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-07-31 9:57 Breno Leitao
2025-08-04 10:25 ` Catalin Marinas [this message]
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