From mboxrd@z Thu Jan 1 00:00:00 1970 From: Al Viro Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Date: Fri, 12 Jul 2019 13:55:52 +0100 Message-ID: <20190712125552.GL17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20190712123924.GK17978@ZenIV.linux.org.uk> Sender: linux-kernel-owner@vger.kernel.org To: Aleksa Sarai Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Fri, Jul 12, 2019 at 01:39:24PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 08:57:45PM +1000, Aleksa Sarai wrote: > > > > > @@ -2350,9 +2400,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags) > > > > s = ERR_PTR(error); > > > > return s; > > > > } > > > > - error = dirfd_path_init(nd); > > > > - if (unlikely(error)) > > > > - return ERR_PTR(error); > > > > + if (likely(!nd->path.mnt)) { > > > > > > Is that a weird way of saying "if we hadn't already called dirfd_path_init()"? > > > > Yes. I did it to be more consistent with the other "have we got the > > root" checks elsewhere. Is there another way you'd prefer I do it? > > "Have we got the root" checks are inevitable evil; here you are making the > control flow in a single function hard to follow. > > I *think* what you are doing is > absolute pathname, no LOOKUP_BENEATH: > set_root > error = nd_jump_root(nd) > else > error = dirfd_path_init(nd) > return unlikely(error) ? ERR_PTR(error) : s; > which should be a lot easier to follow (not to mention shorter), but I might > be missing something in all of that. PS: if that's what's going on, I would be tempted to turn the entire path_init() part into this: if (flags & LOOKUP_BENEATH) while (*s == '/') s++; in the very beginning (plus the handling of nd_jump_root() prototype change, but that belongs with nd_jump_root() change itself, obviously). Again, I might be missing something here... From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zeniv.linux.org.uk ([195.92.253.2]:38082 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727096AbfGLM4P (ORCPT ); Fri, 12 Jul 2019 08:56:15 -0400 Date: Fri, 12 Jul 2019 13:55:52 +0100 From: Al Viro Subject: Re: [PATCH v9 05/10] namei: O_BENEATH-style path resolution flags Message-ID: <20190712125552.GL17978@ZenIV.linux.org.uk> References: <20190706145737.5299-1-cyphar@cyphar.com> <20190706145737.5299-6-cyphar@cyphar.com> <20190712043341.GI17978@ZenIV.linux.org.uk> <20190712105745.nruaftgeat6irhzr@yavin> <20190712123924.GK17978@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190712123924.GK17978@ZenIV.linux.org.uk> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Aleksa Sarai Cc: Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Christian Brauner , David Drysdale , Andy Lutomirski , Linus Torvalds , Eric Biederman , Andrew Morton , Alexei Starovoitov , Kees Cook , Jann Horn , Tycho Andersen , Chanho Min , Oleg Nesterov , Aleksa Sarai , containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-xtensa@linux-xtensa.org, sparclinux@vger.kernel.org Message-ID: <20190712125552.pcAv3Ay3Sme0Axm_Vz_l7Udk5tGOxZUVoZEBDMDfDl8@z> On Fri, Jul 12, 2019 at 01:39:24PM +0100, Al Viro wrote: > On Fri, Jul 12, 2019 at 08:57:45PM +1000, Aleksa Sarai wrote: > > > > > @@ -2350,9 +2400,11 @@ static const char *path_init(struct nameidata *nd, unsigned flags) > > > > s = ERR_PTR(error); > > > > return s; > > > > } > > > > - error = dirfd_path_init(nd); > > > > - if (unlikely(error)) > > > > - return ERR_PTR(error); > > > > + if (likely(!nd->path.mnt)) { > > > > > > Is that a weird way of saying "if we hadn't already called dirfd_path_init()"? > > > > Yes. I did it to be more consistent with the other "have we got the > > root" checks elsewhere. Is there another way you'd prefer I do it? > > "Have we got the root" checks are inevitable evil; here you are making the > control flow in a single function hard to follow. > > I *think* what you are doing is > absolute pathname, no LOOKUP_BENEATH: > set_root > error = nd_jump_root(nd) > else > error = dirfd_path_init(nd) > return unlikely(error) ? ERR_PTR(error) : s; > which should be a lot easier to follow (not to mention shorter), but I might > be missing something in all of that. PS: if that's what's going on, I would be tempted to turn the entire path_init() part into this: if (flags & LOOKUP_BENEATH) while (*s == '/') s++; in the very beginning (plus the handling of nd_jump_root() prototype change, but that belongs with nd_jump_root() change itself, obviously). Again, I might be missing something here...