From: Aleksa Sarai <cyphar@cyphar.com> To: Al Viro <viro@zeniv.linux.org.uk> Cc: linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Alexei Starovoitov <ast@kernel.org>, linux-kernel@vger.kernel.org, David Howells <dhowells@redhat.com>, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Christian Brauner <christian.brauner@ubuntu.com>, Jiri Olsa <jolsa@redhat.com>, linux-arch@vger.kernel.org, linux-s390@vger.kernel.org, Tycho Andersen <tycho@tycho.ws>, Aleksa Sarai <asarai@suse.de>, Shuah Khan <shuah@kernel.org>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Ingo Molnar <mingo@redhat.com>, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook <keescook@chromium.org>, Arnd Bergmann <arnd@arndb.de>, Jann Horn <jannh@google.com>, linuxppc-dev@lists.ozlabs.org, linux-m68k@lists.linux-m68k.org, Andy Lutomirski <luto@kernel.org>, Shuah Khan <skhan@linuxfoundation.org>, Namhyung Kim <namhyung@kernel.org>, David Drysdale <drysdale@google.com>, Christian Brauner <christian@brauner.io>, "J. Bruce Fields" <bfields@fieldses.org>, libc-alpha@sourceware.org, linux-parisc@vger.kernel.org, linux-api@vger.kernel.org, Chanho Min <chanho.min@lge.com>, Jeff Layton <jlayton@kernel.org>, Oleg Nesterov <oleg@redhat.com>, Eric Biederman <ebiederm@xmission.com>, linux-alpha@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, containers@lists.linux-foundation.org Subject: Re: [PATCH v15 5/9] namei: LOOKUP_IN_ROOT: chroot-like scoped resolution Date: Wed, 13 Nov 2019 14:55:42 +1100 [thread overview] Message-ID: <20191113035542.3ckc7oudahn3xtnj@yavin.dot.cyphar.com> (raw) In-Reply-To: <20191113025941.GE26530@ZenIV.linux.org.uk> [-- Attachment #1: Type: text/plain, Size: 2141 bytes --] On 2019-11-13, Al Viro <viro@zeniv.linux.org.uk> wrote: > On Wed, Nov 13, 2019 at 01:44:14PM +1100, Aleksa Sarai wrote: > > On 2019-11-13, Al Viro <viro@zeniv.linux.org.uk> wrote: > > > On Tue, Nov 05, 2019 at 08:05:49PM +1100, Aleksa Sarai wrote: > > > > > > > @@ -2277,12 +2277,20 @@ static const char *path_init(struct nameidata *nd, unsigned flags) > > > > > > > > nd->m_seq = read_seqbegin(&mount_lock); > > > > > > > > - /* Figure out the starting path and root (if needed). */ > > > > - if (*s == '/') { > > > > + /* Absolute pathname -- fetch the root. */ > > > > + if (flags & LOOKUP_IN_ROOT) { > > > > + /* With LOOKUP_IN_ROOT, act as a relative path. */ > > > > + while (*s == '/') > > > > + s++; > > > > > > Er... Why bother skipping slashes? I mean, not only link_path_walk() > > > will skip them just fine, you are actually risking breakage in this: > > > if (*s && unlikely(!d_can_lookup(dentry))) { > > > fdput(f); > > > return ERR_PTR(-ENOTDIR); > > > } > > > which is downstream from there with you patch, AFAICS. > > > > I switched to stripping the slashes at your suggestion a few revisions > > ago[1], and had (wrongly) assumed we needed to handle "/" somehow in > > path_init(). But you're quite right about link_path_walk() -- and I'd be > > more than happy to drop it. > > That, IIRC, was about untangling the weirdness around multiple calls of > dirfd_path_init() and basically went "we might want just strip the slashes > in case of that flag very early in the entire thing, so that later the > normal logics for absolute/relative would DTRT". Ah okay, I'd misunderstood the point you were making in that thread. > Since your check is right next to checking for absolute pathnames (and > not in the very beginning of path_init()), we might as well turn the > check for absolute pathname into *s == '/' && !(flags & > LOOKUP_IN_ROOT) and be done with that. Yup, agreed. -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/> [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 228 bytes --]
WARNING: multiple messages have this Message-ID (diff)
From: Aleksa Sarai <cyphar@cyphar.com> To: Al Viro <viro@zeniv.linux.org.uk> Cc: Jeff Layton <jlayton@kernel.org>, "J. Bruce Fields" <bfields@fieldses.org>, Arnd Bergmann <arnd@arndb.de>, David Howells <dhowells@redhat.com>, Shuah Khan <shuah@kernel.org>, Shuah Khan <skhan@linuxfoundation.org>, Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Christian Brauner <christian.brauner@ubuntu.com>, Eric Biederman <ebiederm@xmission.com>, Andy Lutomirski <luto@kernel.org>, Andrew Morton <akpm@linux-foundation.org>, Alexei Starovoitov <ast@kernel.org>, Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>, Tycho Andersen <tycho@tycho.ws>, David Drysdale <drysdale@google.com>, Chanho Min <chanho.min@lge.com>, Oleg Nesterov <oleg@redhat.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>, Christian Brauner <christian@brauner.io>, Aleksa Sarai <asarai@suse.de>, Linus Torvalds <torvalds@linux-foundation.org>, containers@lists.linux-foundation.org, linux-alpha@vger.kernel.org, linux-api@vger.kernel.org, libc-alpha@sourceware.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 Subject: Re: [PATCH v15 5/9] namei: LOOKUP_IN_ROOT: chroot-like scoped resolution Date: Wed, 13 Nov 2019 14:55:42 +1100 [thread overview] Message-ID: <20191113035542.3ckc7oudahn3xtnj@yavin.dot.cyphar.com> (raw) Message-ID: <20191113035542.TrTqcU4fxZQgNSHNpKuOx-uLPnYBMAf1YAg95qSB4q4@z> (raw) In-Reply-To: <20191113025941.GE26530@ZenIV.linux.org.uk> [-- Attachment #1: Type: text/plain, Size: 2141 bytes --] On 2019-11-13, Al Viro <viro@zeniv.linux.org.uk> wrote: > On Wed, Nov 13, 2019 at 01:44:14PM +1100, Aleksa Sarai wrote: > > On 2019-11-13, Al Viro <viro@zeniv.linux.org.uk> wrote: > > > On Tue, Nov 05, 2019 at 08:05:49PM +1100, Aleksa Sarai wrote: > > > > > > > @@ -2277,12 +2277,20 @@ static const char *path_init(struct nameidata *nd, unsigned flags) > > > > > > > > nd->m_seq = read_seqbegin(&mount_lock); > > > > > > > > - /* Figure out the starting path and root (if needed). */ > > > > - if (*s == '/') { > > > > + /* Absolute pathname -- fetch the root. */ > > > > + if (flags & LOOKUP_IN_ROOT) { > > > > + /* With LOOKUP_IN_ROOT, act as a relative path. */ > > > > + while (*s == '/') > > > > + s++; > > > > > > Er... Why bother skipping slashes? I mean, not only link_path_walk() > > > will skip them just fine, you are actually risking breakage in this: > > > if (*s && unlikely(!d_can_lookup(dentry))) { > > > fdput(f); > > > return ERR_PTR(-ENOTDIR); > > > } > > > which is downstream from there with you patch, AFAICS. > > > > I switched to stripping the slashes at your suggestion a few revisions > > ago[1], and had (wrongly) assumed we needed to handle "/" somehow in > > path_init(). But you're quite right about link_path_walk() -- and I'd be > > more than happy to drop it. > > That, IIRC, was about untangling the weirdness around multiple calls of > dirfd_path_init() and basically went "we might want just strip the slashes > in case of that flag very early in the entire thing, so that later the > normal logics for absolute/relative would DTRT". Ah okay, I'd misunderstood the point you were making in that thread. > Since your check is right next to checking for absolute pathnames (and > not in the very beginning of path_init()), we might as well turn the > check for absolute pathname into *s == '/' && !(flags & > LOOKUP_IN_ROOT) and be done with that. Yup, agreed. -- Aleksa Sarai Senior Software Engineer (Containers) SUSE Linux GmbH <https://www.cyphar.com/> [-- Attachment #2: signature.asc --] [-- Type: application/pgp-signature, Size: 228 bytes --]
next prev parent reply other threads:[~2019-11-13 4:01 UTC|newest] Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-05 9:05 [PATCH v15 0/9] open: introduce openat2(2) syscall Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 1/9] namei: LOOKUP_NO_SYMLINKS: block symlink resolution Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 2/9] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution Aleksa Sarai 2019-11-13 1:24 ` Al Viro 2019-11-13 1:24 ` Al Viro 2019-11-05 9:05 ` [PATCH v15 3/9] namei: LOOKUP_NO_XDEV: block mountpoint crossing Aleksa Sarai 2019-11-13 1:36 ` Al Viro 2019-11-13 1:36 ` Al Viro 2019-11-14 4:49 ` Aleksa Sarai 2019-11-14 4:49 ` Aleksa Sarai 2019-11-14 5:43 ` Al Viro 2019-11-14 5:43 ` Al Viro 2019-11-14 13:33 ` Aleksa Sarai 2019-11-14 13:33 ` Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 4/9] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution Aleksa Sarai 2019-11-13 1:55 ` Al Viro 2019-11-13 1:55 ` Al Viro 2019-11-13 7:47 ` Aleksa Sarai 2019-11-13 7:47 ` Aleksa Sarai 2019-11-14 4:57 ` Aleksa Sarai 2019-11-14 4:57 ` Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 5/9] namei: LOOKUP_IN_ROOT: chroot-like " Aleksa Sarai 2019-11-13 2:03 ` Al Viro 2019-11-13 2:03 ` Al Viro 2019-11-13 2:44 ` Aleksa Sarai 2019-11-13 2:44 ` Aleksa Sarai 2019-11-13 2:59 ` Al Viro 2019-11-13 2:59 ` Al Viro 2019-11-13 3:55 ` Aleksa Sarai [this message] 2019-11-13 3:55 ` Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 6/9] namei: LOOKUP_{IN_ROOT, BENEATH}: permit limited ".." resolution Aleksa Sarai 2019-11-13 2:09 ` [PATCH v15 6/9] namei: LOOKUP_{IN_ROOT,BENEATH}: " Al Viro 2019-11-13 2:09 ` Al Viro 2019-11-13 7:52 ` Aleksa Sarai 2019-11-13 7:52 ` Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 7/9] open: introduce openat2(2) syscall Aleksa Sarai 2019-11-13 2:29 ` Al Viro 2019-11-13 2:29 ` Al Viro 2019-11-13 2:35 ` Aleksa Sarai 2019-11-13 2:35 ` Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 8/9] selftests: add openat2(2) selftests Aleksa Sarai 2019-11-05 9:05 ` [PATCH v15 9/9] Documentation: path-lookup: mention LOOKUP_MAGICLINK_JUMPED Aleksa Sarai 2019-11-11 13:24 ` [PATCH v15 0/9] open: introduce openat2(2) syscall Aleksa Sarai 2019-11-12 23:01 ` Kees Cook 2019-11-12 23:01 ` Kees Cook 2019-11-12 23:06 ` Christian Brauner 2019-11-12 23:06 ` Christian Brauner 2019-11-13 0:46 ` Aleksa Sarai 2019-11-13 0:46 ` Aleksa Sarai
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