From nobody Sat Feb 7 11:31:40 2026 Received: from out-183.mta0.migadu.com (out-183.mta0.migadu.com [91.218.175.183]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 2B9FD19CC28 for ; Thu, 23 Oct 2025 01:22:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.183 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761182545; cv=none; b=N+WnfYOCCEEB7YIfE/yXUI4+fMHO3dEAOGHNAJuwSLka7YsqLkqQh+ChxDbkza+bYKGap5voemJer2Lhif9E3AkoRwWpgrhOQzHrbmVOYzgZ9brWCG3HKa2dPPN5+pSfBWW44AZLjvuJZj1/f1taRb+gcsoBh3b/A1nCh5eTx9U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761182545; c=relaxed/simple; bh=gFkuFBYwfXjWA+JokwbpcI+zh7N26aE7upFroO/KxXM=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=WGIxy0yx29Dmdi+MZJsu5fok0Z8KM84ZwrwmwXfBM+yuGQ5p7W0D6h9LtjxSue0S74OEEVB796tvilLvVhXOl7SesF8VwEyVx02nYpE2SkJ8btjtlFj4vXiX5PXVhlVhx/AeuKQX/QwRwL5e/9gki7Q9on7gIORZLPewLDS/oCY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=aIRX/LnA; arc=none smtp.client-ip=91.218.175.183 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="aIRX/LnA" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761182530; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=lS0mhQ5R43bGQo27SjH0eAhLsgCq0WUEHmFOE5SKzxw=; b=aIRX/LnASeyDPiwS8a8wyOgL5oKFWk9ymcuT75gnJ0IZOacm3dSpZH/R38T3ReMFFQ40uZ YTSnRX+CgIa/HmXPWYBgk26GFQnodLiOWZUrN0yWnumG744hcTGdK1gW1qKEFdtFIcbgPu 4TDa5R6gAwW0HHQ2ZhxTRUnlAtZ7YEo= From: Hao Ge To: Vlastimil Babka , Andrew Morton , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Suren Baghdasaryan Cc: Shakeel Butt , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Hao Ge Subject: [PATCH] slab: Fix obj_ext is mistakenly considered NULL due to race condition Date: Thu, 23 Oct 2025 09:21:17 +0800 Message-Id: <20251023012117.890883-1-hao.ge@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" From: Hao Ge If two competing threads enter alloc_slab_obj_exts(), and the thread that failed to allocate the object extension vector exits after the one that succeeded, it will mistakenly assume slab->obj_ext is still empty due to its own allocation failure. This will then trigger warnings enforced by CONFIG_MEM_ALLOC_PROFILING_DEBUG checks in the subsequent free path. Therefore, let's add an additional check when alloc_slab_obj_exts fails. Signed-off-by: Hao Ge --- mm/slub.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index d4403341c9df..42276f0cc920 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -2227,9 +2227,12 @@ prepare_slab_obj_exts_hook(struct kmem_cache *s, gfp= _t flags, void *p) slab =3D virt_to_slab(p); if (!slab_obj_exts(slab) && alloc_slab_obj_exts(slab, s, flags, false)) { - pr_warn_once("%s, %s: Failed to create slab extension vector!\n", - __func__, s->name); - return NULL; + /* Recheck if a racing thread has successfully allocated slab->obj_exts.= */ + if (!slab_obj_exts(slab)) { + pr_warn_once("%s, %s: Failed to create slab extension vector!\n", + __func__, s->name); + return NULL; + } } =20 return slab_obj_exts(slab) + obj_to_index(s, slab, p); --=20 2.25.1