From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 72F311AED21; Fri, 23 Aug 2024 14:06:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724421987; cv=none; b=DNe0IqsP6IcvtKLTG4enGqs2ghwd2fYjbDmTbOcxL4cQ18fIHfsV1t/3vyKjjkBuO3frezsl6OnxAiI35Xm8hmnAX1Bkstxx5P9DjHQwSNQ5tW6/G5zfxt99k9SzPpN4H+dTzgh/pGEit2RJAAjJrwTlUy5bnvk4vQrkDbiuGmQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724421987; c=relaxed/simple; bh=s6a75ygW/XR1hPToCJ4pwziJfz1cgmCxHl4xM3zC+eM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=AKkvL80IxrOAWOHQ3gJlk27bBkKiYIp0urJqYznktaXl9I2qvBIJJo0aOFNX2mvjKAdeo27R+7NBoJa0zVSntb6OGGVkJRVjeWAVLUtUNV+CMmvMNGpvO4ev10qGDCKayh83JRa5G/QtRnUHuCQmxM8nUuLSCRL8fPRjDn2WtEo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=liVGzIY6; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="liVGzIY6" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C0377C32786; Fri, 23 Aug 2024 14:06:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1724421987; bh=s6a75ygW/XR1hPToCJ4pwziJfz1cgmCxHl4xM3zC+eM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=liVGzIY6pXWLvKBtiYXkoKSln3i1CqG7+GUPRTqMm9d8FwqY7VDwTfFX4cJmXjXYB /8wo6CpVcSP8ZPMrNQJGDcFBVfos/U/dh9K/FWydcxNCMim6cyq/m8JQULD/HT0xL6 LIJje3lpa3SQkI0Btm7xEEa+URyJCaCVHl8Xy+1HYqGXxxJ7dPfi2NGJHhM3m+w5dl NN4aG4GhjLSmG0SFdaULm4fBWT0XvpAgxInoEZvOTtshlhyLrfoJKiba/xsyE5mM7D mp5VCiMkdGZxs/izYFAMadwmBq7rZ1o0BJgFeackbsjNMIU5NCUXo3CJihcf2RnxOf HwyT4uEI1S6nw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kent Overstreet , Sasha Levin Subject: [PATCH AUTOSEL 5.4 7/7] lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc() Date: Fri, 23 Aug 2024 10:06:02 -0400 Message-ID: <20240823140611.1975950-7-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240823140611.1975950-1-sashal@kernel.org> References: <20240823140611.1975950-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 5.4.282 Content-Transfer-Encoding: 8bit From: Kent Overstreet [ Upstream commit b2f11c6f3e1fc60742673b8675c95b78447f3dae ] If we need to increase the tree depth, allocate a new node, and then race with another thread that increased the tree depth before us, we'll still have a preallocated node that might be used later. If we then use that node for a new non-root node, it'll still have a pointer to the old root instead of being zeroed - fix this by zeroing it in the cmpxchg failure path. Signed-off-by: Kent Overstreet Signed-off-by: Sasha Levin --- lib/generic-radix-tree.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c index f25eb111c0516..34d3ac52de894 100644 --- a/lib/generic-radix-tree.c +++ b/lib/generic-radix-tree.c @@ -131,6 +131,8 @@ void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset, if ((v = cmpxchg_release(&radix->root, r, new_root)) == r) { v = new_root; new_node = NULL; + } else { + new_node->children[0] = NULL; } } -- 2.43.0