From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 7577E44AB91; Tue, 21 Jul 2026 22:36:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784673372; cv=none; b=W/F849b7jU8KUamHKU/RF8mb0YUeyOL0wLAXVJr1aRmm39cW85HvuQADx43oQ/ULLnM4V1c6Rz1e29pwaIGfyW6KA72beSAnCaNxSQxW9Tjzgn33ARZFua4baGIowIONOzqTZuyO4xg/Wg9Wbz7mBhQq06hF3qv8K18EXnaKr3c= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784673372; c=relaxed/simple; bh=Mvqz4A25IYcwe9gFSWNmqA1Jo2t8HsocHBEPfkESn6s=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Lqrl4RIRvLdwM2uAavOxfm5sHd062a8VpzdloEzO5Rs4sHxqd1d1i1CsL5+PJao/Xe5xXrscY/WSJ4XOrOiN/fnceGc4Ua46VM0CVkP/tFHHrXemfSkD4IGveCH3x+Yt4tZpGC5YrDtZeZVz8/J8nTVLfGeT5DW3mYTHm6bxRIo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=SB01bbDX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="SB01bbDX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DBA581F000E9; Tue, 21 Jul 2026 22:36:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1784673370; bh=vDANF5ZAkdkI2ERNmZn9g9/pAUynu7tOVlPOzhQ7mt4=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SB01bbDX72NSH7ExrzRvXW/jQSRn3UjZJlLPp7IaVBtEheiHVyMvdTIwxmeflpluE c70KVlG+apsPEx6bfsLNWcCnRxp8eXQuBXE1gQ5/5fPyMT6PGVzmjNqJkkcPlKD9wX TathYaOyRmOq7QOuGXouA4hfWd7jHkpdRBHnHAA8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Trond Myklebust , Benjamin Coddington , Anna Schumaker Subject: [PATCH 5.10 138/699] NFSv4: include MAY_WRITE in open permission mask for O_TRUNC Date: Tue, 21 Jul 2026 17:18:17 +0200 Message-ID: <20260721152358.822795855@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260721152355.667394603@linuxfoundation.org> References: <20260721152355.667394603@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Benjamin Coddington commit 5140f099ecd8a2f2808b7f7b720ee1bad8468974 upstream. POSIX requires write permission to truncate a file, so an open() that specifies O_TRUNC must be authorized for write access regardless of the O_ACCMODE access mode. nfs_open_permission_mask() builds the access mask passed to nfs_may_open(), which is the local authorization gate for OPENs the client serves itself from a cached write delegation via the can_open_delegated() path in nfs4_try_open_cached(). The mask is derived from O_ACCMODE alone, so an open(O_RDONLY | O_TRUNC) against a file the caller cannot write requests only MAY_READ and passes the local check. The OPEN is then satisfied locally and the truncation is issued to the server as a SETATTR(size=0) over the delegation stateid, which the server accepts under standard write-delegation semantics. POSIX requires that this open fail with EACCES. Include MAY_WRITE in the mask whenever O_TRUNC is set so the local check matches the access the server would have enforced. Suggested-by: Trond Myklebust Fixes: af22f94ae02a ("NFSv4: Simplify _nfs4_do_access()") Cc: stable@vger.kernel.org Signed-off-by: Benjamin Coddington Signed-off-by: Anna Schumaker Signed-off-by: Greg Kroah-Hartman --- fs/nfs/dir.c | 2 ++ 1 file changed, 2 insertions(+) --- a/fs/nfs/dir.c +++ b/fs/nfs/dir.c @@ -2803,6 +2803,8 @@ static int nfs_open_permission_mask(int mask |= MAY_READ; if ((openflags & O_ACCMODE) != O_RDONLY) mask |= MAY_WRITE; + if (openflags & O_TRUNC) + mask |= MAY_WRITE; } return mask;