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arc=none smtp.client-ip=62.89.141.173 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707013064; cv=none; b=BOgqL7YbO7aAqSDpdIwJkxsWqYUzlqGYrqq79sNVruofc8l6bCaAWnaPO7uf9dlLdtvMpYdJ90pGFuAtOeApsAEQQv2vNXnrx9s+Mi/iYFEbjw56UkZTlDUAE11fXy+MW39PYuI+ih7kS/e4XJ82pi7d1a+rzde6c5uPon/0bQc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1707013064; c=relaxed/simple; bh=v5nm9WdCUwUgJfQ97cmtXjLDq45y1UqLvQaZ0A5z2ZY=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=mcOxfLIfb2dkG+Y5phLajGHnPekorfz+l78YgV2ViDcvRGz0UBcv9AaHl94c9TeVShT9uIa27pCVAFS07C4MPSX9KgolojM6pbuteDGa7ZtaK8sWUX87XTnefrUcn+syAKAOgYsLeVeoBx7vSmy3ideWTou9dlXIlIMLlL2Mxqk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk; spf=none smtp.mailfrom=ftp.linux.org.uk; dkim=pass (2048-bit key) header.d=linux.org.uk header.i=@linux.org.uk header.b=LGcxzo4I; arc=none smtp.client-ip=62.89.141.173 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zeniv.linux.org.uk Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=ftp.linux.org.uk DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=linux.org.uk; s=zeniv-20220401; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=WNs3vukbXJtl12Oxlgybl8Hl88cxUtaVDUYMxN0ihgM=; b=LGcxzo4IlqtZEUOa+v0SpEXnZ2 DQTG2ASGJxbT8A1OnFm4F9VWP9wkAiedcZhFYqXPzd5TMBUJ4k4H1KScdcc1Os45IRjg3QN0b+7FK fyLWpO/DTbglgPM8gcpubs7ZL9gghTV4JoaRg37REEWWmhLGJl8CZeFzNsKHrA73MUu0vvzMgBWMe ++e7gAMZ/ItTOzFUpw83GE7onAOlJGzWnsfVFuyA03K8I2Bo6kidvJ1ohmTwruTuvISmmg/52K6bT ZS88i3QMl+eKMct5NUDkCCeMZeXlhWn2TXNe1BMXcFSLLwoB9iHlUZmnk6FNzzqzDlUoAIZLS6eXL QHGwd72g==; Received: from viro by zeniv.linux.org.uk with local (Exim 4.96 #2 (Red Hat Linux)) id 1rWS4i-004rCp-0J; Sun, 04 Feb 2024 02:17:40 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: Linus Torvalds , Christian Brauner , linux-ext4@vger.kernel.org, linux-nfs@vger.kernel.org, Miklos Szeredi , linux-cifs@vger.kernel.org Subject: [PATCH 02/13] rcu pathwalk: prevent bogus hard errors from may_lookup() Date: Sun, 4 Feb 2024 02:17:28 +0000 Message-Id: <20240204021739.1157830-2-viro@zeniv.linux.org.uk> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20240204021739.1157830-1-viro@zeniv.linux.org.uk> References: <20240204021436.GH2087318@ZenIV> <20240204021739.1157830-1-viro@zeniv.linux.org.uk> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Sender: Al Viro If lazy call of ->permission() returns a hard error, check that try_to_unlazy() succeeds before returning it. That both makes life easier for ->permission() instances and closes the race in ENOTDIR handling - it is possible that positive d_can_lookup() seen in link_path_walk() applies to the state *after* unlink() + mkdir(), while nd->inode matches the state prior to that. Normally seeing e.g. EACCES from permission check in rcu pathwalk means that with some timings non-rcu pathwalk would've run into the same; however, running into a non-executable regular file in the middle of a pathname would not get to permission check - it would fail with ENOTDIR instead. Signed-off-by: Al Viro Reviewed-by: Christian Brauner --- fs/namei.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/fs/namei.c b/fs/namei.c index 4e0de939fea1..9342fa6a38c2 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1717,7 +1717,11 @@ static inline int may_lookup(struct mnt_idmap *idmap, { if (nd->flags & LOOKUP_RCU) { int err = inode_permission(idmap, nd->inode, MAY_EXEC|MAY_NOT_BLOCK); - if (err != -ECHILD || !try_to_unlazy(nd)) + if (!err) // success, keep going + return 0; + if (!try_to_unlazy(nd)) + return -ECHILD; // redo it all non-lazy + if (err != -ECHILD) // hard error return err; } return inode_permission(idmap, nd->inode, MAY_EXEC);