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 7C2DD1AB6FD; Sat, 12 Oct 2024 11:27:57 +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=1728732477; cv=none; b=OM2RBWhnhCvSxqu2Anr+EbBoRi3X9LhiQeNCMQFQPJhfq6K0UQMgKdt++0PMi2NyXAfbQwQyd2LltAlcbJZIcAIIlZKmrnRDSAhRopuhMQhHZqnIE/0Pf6hzlBjl2r5Q+Js1uZ3utUqUS50ifLGYU/8LVET2msqisLrH8xN20oM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728732477; c=relaxed/simple; bh=UiqWGB4fidTn7hEicA8WF8H3Yu5kNYzn7AfdgvBKixA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=mbiNcy15AL0sC5Lf+CYYbvGp383QGuUNmggMiYw8gjdAWYcpd8OTV3wXgiPMnFmckZuP18LBOjgi7Ph5OTKwV3b5iEKukK/RpKGMarY7ysBf3gcoPI8S3FJC9tpu4vj3EbRxzvcVmaHdKb/q5JCNEXcRIMyWjBjjCZtJOEx2xvw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ctPu+oud; 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="ctPu+oud" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CD934C4CECF; Sat, 12 Oct 2024 11:27:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728732477; bh=UiqWGB4fidTn7hEicA8WF8H3Yu5kNYzn7AfdgvBKixA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ctPu+oudbMjDPPeO15Mi9uoPM0QVNrRBL2BbTKEuBV5Gp/nKq+LSzeaH+Snsua4Ya YrSn6Sa4ffESKIkwVw7k4CKZAIXjXihUdyHyWIBHehviOc6FoQ4ixrP9xZA911cIGR Qo2jZRBZzTwIz+dAt7oGf8Dmm3Y34479TD4d3KsUbCrHTVx+D/mv5Khj8gpjK3Hexb 6Q1m9ADdj6KLP3F0tWn+wGZXCXHWwxdtsDoYtmPgBZ+duQItLIQjxUrzLIF8lj0Ayo tlG7EmOSq0uMQgRpSscYKB5gmn6e3aVoC+KHCreWg+4LWU+wbgrZvNJzp7euB9sfvY yzQnjqG25kOyg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Kent Overstreet , Sasha Levin Subject: [PATCH AUTOSEL 6.6 18/20] lib/generic-radix-tree.c: Fix rare race in __genradix_ptr_alloc() Date: Sat, 12 Oct 2024 07:26:50 -0400 Message-ID: <20241012112715.1763241-18-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20241012112715.1763241-1-sashal@kernel.org> References: <20241012112715.1763241-1-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 6.6.56 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 7dfa88282b006..78f081d695d0b 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