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Thu, 31 Jul 2025 02:57:31 -0700 (PDT) Received: from localhost ([2a03:2880:30ff:70::]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-af91a1e8992sm83409966b.91.2025.07.31.02.57.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 31 Jul 2025 02:57:30 -0700 (PDT) From: Breno Leitao Date: Thu, 31 Jul 2025 02:57:18 -0700 Subject: [PATCH] mm/kmemleak: avoid deadlock by moving pr_warn() outside kmemleak_lock MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20250731-kmemleak_lock-v1-1-728fd470198f@debian.org> X-B4-Tracking: v=1; b=H4sIAP49i2gC/x3MWwqDMBQFwK1czreBaFJCs5UiEuypXuKLBKQg7 r3QWcBcqCzKiigXCk+tum+I0jaCcU7bRKNvREFnu4cNrjV55bow5WHZx2w8rQ/eMYUn0QiOwo9 +/9+rv+8fiSpraV8AAAA= X-Change-ID: 20250731-kmemleak_lock-4e04743ea79e To: Catalin Marinas , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, stable@kenrel.org, kernel-team@meta.com, Breno Leitao X-Mailer: b4 0.15-dev-dd21f X-Developer-Signature: v=1; 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a=openpgp; fpr=AC8539A6E8F46702CA4A439B35A3939FFC78776D X-Rspamd-Queue-Id: 350C540003 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: fjpzih8fe479ef7jjwg3ztgegb7isexz X-HE-Tag: 1753955852-600727 X-HE-Meta: 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 AAXEPGiV D25HP1jDK0aQWEwvCmYhYWu6ETq0UfXLa0CNkhWLzJYtn5QbpkQp/dDqtT3Rwlb8NB2cGTpDBA1ASAdH93twieDTcVXgZV9n9phVos/2Qm8AnAeYGvEgrGUxQFwcPngydLl5WgJ9q41jtHfFspHTZ4LsmhoUWXIUjEZthbCil951Mj68v+Y3/kBW3kEmcX3Dd7EGeHIH+0D5RuqyUCalKmbyCJp41XhxJIEEubzWNa3D5ex4FT6Pa0hrHLBlxyvMII9I6rDzj+3D3mbQkl1UUJ8/eaANI7swJ7cSttiK662vUj+4BFy3iP1i4DTuui2RwmbrAnuQIN512tHEHxnOoXVQBa6a2vWEjfVKPVJH9DRK3NpZn85zb5iyC0LJTz5IYZZ36udXafeINEajBvUI8O+Rw9Ydoiy+m/LXxdduXYnPvFXoUKXzREMKIKkTZrt3FMyPL4vajTsBXsnTqn3Wu8eTByLPwquGhxSiX X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 Fixes: c5665868183fec ("mm: kmemleak: use the memory pool for early allocations") Signed-off-by: Breno Leitao --- mm/kmemleak.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/kmemleak.c b/mm/kmemleak.c index 8d588e6853110..e0333455c7384 100644 --- a/mm/kmemleak.c +++ b/mm/kmemleak.c @@ -470,6 +470,7 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp) { unsigned long flags; struct kmemleak_object *object; + bool warn = false; /* try the slab allocator first */ if (object_cache) { @@ -488,8 +489,10 @@ static struct kmemleak_object *mem_pool_alloc(gfp_t gfp) else if (mem_pool_free_count) object = &mem_pool[--mem_pool_free_count]; else - pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); + warn = true; raw_spin_unlock_irqrestore(&kmemleak_lock, flags); + if (warn) + pr_warn_once("Memory pool empty, consider increasing CONFIG_DEBUG_KMEMLEAK_MEM_POOL_SIZE\n"); return object; } --- base-commit: 260f6f4fda93c8485c8037865c941b42b9cba5d2 change-id: 20250731-kmemleak_lock-4e04743ea79e Best regards, -- Breno Leitao