From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Google-Smtp-Source: AG47ELtsj/ctQJoUCuRrd9MgCQZjbiMVbAvY8Hj3Lc6CqwYoWR8deNh38zv0AiQP0nNpI78tOeDU ARC-Seal: i=1; a=rsa-sha256; t=1521301411; cv=none; d=google.com; s=arc-20160816; b=BEulLf7fFd2rBEyZtlWTIFg9ZICCkGwTiORyaVAtw038hJG5uQKEDrcAKSFs5M8e2H e7mtTnOZrKV6/z4//caTnKx+RHPJU9rBdLXHAOwYDLy9JCs0wX4+7KifTiz8rfdoQE4X ynKyEYPA4uAIDORoOwq7+spAh6IYEwIHPLLvKwG2Dq+v1qMHezNx2u7K9pQqvX3JxmHk ttJh+31dZo7zyVRilKVWezaQkuGA459R7EwkFhFcGCeVByRRgI009BVMC9SY8miBaqKE q+B5WO+tgga2hSw7qkTQR1Ppd+yAM1CEGuDAwLFlt9tZ2VRAqaCECWaMPqwOvat/1yp7 9X2g== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=content-transfer-encoding:mime-version:references:in-reply-to:date :cc:to:from:subject:message-id:dmarc-filter :arc-authentication-results; bh=qm+gXPn0kY4Yf4JLu66CW0JZ4HANvk8POYMMXcHedhE=; b=iwIXndNL7YzEsLjoBBdsxpdVGbNC1oYcL8Gl8zAWPf9wz3MDnlNlKYsWysLW2mewH5 9RiVU4qfGClTVpKrxZNIzDZWDSWmQqgJNPggeGyTqLDkZ+/7pKWOa0H2HG1MR/UQL3zp GN9rSsSq3ZgOf5zJ9v1G0RiqklfT+yRyF/XFIJKtfMetU/PZfGkZy2O7uzY2hUP6+bhf dfAYaYTU0t2NvebYjlvUeF6sM9Qtiepyh98MCluSyFEBUmuQFIA1h+ensRXcw7hxq283 120YSYTHrgTXKWvlpOO3hY+wkcMbu3PjSFR9npYWklhiNaHKFgNoTfABFa9BXH3JHWpF vERg== ARC-Authentication-Results: i=1; mx.google.com; spf=pass (google.com: best guess record for domain of jlayton@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=jlayton@kernel.org Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of jlayton@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=jlayton@kernel.org DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C73920855 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jlayton@kernel.org Message-ID: <1521301408.4064.4.camel@kernel.org> Subject: Re: [PATCH] locks: change POSIX lock ownership on execve when files_struct is displaced From: Jeff Layton To: Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, "J. Bruce Fields" , Thomas Gleixner , "Daniel P ." =?ISO-8859-1?Q?Berrang=E9?= , Kate Stewart , Dan Williams , Philippe Ombredanne , Greg Kroah-Hartman Date: Sat, 17 Mar 2018 11:43:28 -0400 In-Reply-To: <20180317150533.GM30522@ZenIV.linux.org.uk> References: <20180317142520.30520-1-jlayton@kernel.org> <20180317150533.GM30522@ZenIV.linux.org.uk> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 (3.26.6-1.fc27) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595195233416759536?= X-GMAIL-MSGID: =?utf-8?q?1595200148715382874?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On Sat, 2018-03-17 at 15:05 +0000, Al Viro wrote: > On Sat, Mar 17, 2018 at 10:25:20AM -0400, Jeff Layton wrote: > > From: Jeff Layton > > > > POSIX mandates that open fds and their associated file locks should be > > preserved across an execve. This works, unless the process is > > multithreaded at the time that execve is called. > > > > In that case, we'll end up unsharing the files_struct but the locks will > > still have their fl_owner set to the address of the old one. Eventually, > > when the other threads die and the last reference to the old > > files_struct is put, any POSIX locks get torn down since it looks like > > a close occurred on them. > > > > The result is that all of your open files will be intact with none of > > the locks you held before execve. The simple answer to this is "use OFD > > locks", but this is a nasty surprise and it violates the spec. > > > > On a successful execve, change ownership of any POSIX file_locks > > associated with the old files_struct to the new one, if we ended up > > swapping it out. > > TBH, I don't like the way you implement that. Why not simply use > iterate_fd()? Ahh, I wasn't aware of it. I copied the loop in change_lock_owners from close_files. I'll have a look at iterate_fd(). Thanks, -- Jeff Layton