From: Aleksa Sarai <cyphar@cyphar.com> To: Al Viro <viro@zeniv.linux.org.uk>, 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>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>, Jonathan Corbet <corbet@lwn.net> Cc: linux-ia64@vger.kernel.org, linux-doc@vger.kernel.org, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Rasmus Villemoes <linux@rasmusvillemoes.dk>, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, sparclinux@vger.kernel.org, Christian Brauner <christian.brauner@ubuntu.com>, linux-api@vger.kernel.org, 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>, linux-sh@vger.kernel.org, David Drysdale <drysdale@google.com>, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, linux-xtensa@linux-xtensa.org, Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>, linuxppc-dev@lists.ozlabs.org, dev@opencontainers.org, Aleksa Sarai <cyphar@cyphar.com>, Andy Lutomirski <luto@kernel.org>, Namhyung Kim <namhyung@kernel.org>, bpf@vger.kernel.org, Christian Brauner <christian@brauner.io>, libc-alpha@sourceware.org, linux-parisc@vger.kernel.org, linux-m68k@lists.linux-m68k.org, netdev@vger.kernel.org, Chanho Min <chanho.min@lge.com>, 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: [PATCH v17 07/13] namei: LOOKUP_NO_XDEV: block mountpoint crossing Date: Sun, 17 Nov 2019 12:17:07 +1100 [thread overview] Message-ID: <20191117011713.13032-8-cyphar@cyphar.com> (raw) In-Reply-To: <20191117011713.13032-1-cyphar@cyphar.com> /* Background. */ The need to contain path operations within a mountpoint has been a long-standing usecase that userspace has historically implemented manually with liberal usage of stat(). find, rsync, tar and many other programs implement these semantics -- but it'd be much simpler to have a fool-proof way of refusing to open a path if it crosses a mountpoint. This is part of a refresh of Al's AT_NO_JUMPS patchset[1] (which was a variation on David Drysdale's O_BENEATH patchset[2], which in turn was based on the Capsicum project[3]). /* Userspace API. */ LOOKUP_NO_XDEV will be exposed to userspace through openat2(2). /* Semantics. */ Unlike most other LOOKUP flags (most notably LOOKUP_FOLLOW), LOOKUP_NO_XDEV applies to all components of the path. With LOOKUP_NO_XDEV, any path component which crosses a mount-point during path resolution (including "..") will yield an -EXDEV. Absolute paths, absolute symlinks, and magic-links will only yield an -EXDEV if the jump involved changing mount-points. /* Testing. */ LOOKUP_NO_XDEV is tested as part of the openat2(2) selftests. [1]: https://lore.kernel.org/lkml/20170429220414.GT29622@ZenIV.linux.org.uk/ [2]: https://lore.kernel.org/lkml/1415094884-18349-1-git-send-email-drysdale@google.com/ [3]: https://lore.kernel.org/lkml/1404124096-21445-1-git-send-email-drysdale@google.com/ Cc: Christian Brauner <christian.brauner@ubuntu.com> Suggested-by: David Drysdale <drysdale@google.com> Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Suggested-by: Andy Lutomirski <luto@kernel.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> --- fs/namei.c | 31 +++++++++++++++++++++++++++---- include/linux/namei.h | 1 + 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 415a897729c8..321c8ad5d6b3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -838,6 +838,11 @@ static inline void path_to_nameidata(const struct path *path, static int nd_jump_root(struct nameidata *nd) { + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + /* Absolute path arguments to path_init() are allowed. */ + if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt) + return -EXDEV; + } if (!nd->root.mnt) { int error = set_root(nd); if (error) @@ -873,6 +878,12 @@ int nd_jump_link(struct path *path) if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS)) goto err; + error = -EXDEV; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + if (nd->path.mnt != path->mnt) + goto err; + } + path_put(&nd->path); nd->path = *path; nd->inode = nd->path.dentry->d_inode; @@ -1280,12 +1291,16 @@ static int follow_managed(struct path *path, struct nameidata *nd) break; } - if (need_mntput && path->mnt == mnt) - mntput(path->mnt); + if (need_mntput) { + if (path->mnt == mnt) + mntput(path->mnt); + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + ret = -EXDEV; + else + nd->flags |= LOOKUP_JUMPED; + } if (ret == -EISDIR || !ret) ret = 1; - if (need_mntput) - nd->flags |= LOOKUP_JUMPED; if (unlikely(ret < 0)) path_put_conditional(path, nd); return ret; @@ -1342,6 +1357,8 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, mounted = __lookup_mnt(path->mnt, path->dentry); if (!mounted) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return false; path->mnt = &mounted->mnt; path->dentry = mounted->mnt.mnt_root; nd->flags |= LOOKUP_JUMPED; @@ -1388,6 +1405,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (&mparent->mnt == nd->path.mnt) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -ECHILD; /* we know that mountpoint was pinned */ nd->path.dentry = mountpoint; nd->path.mnt = &mparent->mnt; @@ -1402,6 +1421,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (!mounted) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -ECHILD; nd->path.mnt = &mounted->mnt; nd->path.dentry = mounted->mnt.mnt_root; inode = nd->path.dentry->d_inode; @@ -1500,6 +1521,8 @@ static int follow_dotdot(struct nameidata *nd) } if (!follow_up(&nd->path)) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -EXDEV; } follow_mount(&nd->path); nd->inode = nd->path.dentry->d_inode; diff --git a/include/linux/namei.h b/include/linux/namei.h index 1573b8493d98..25ee88c4acb1 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -42,6 +42,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; /* Scoping flags for lookup. */ #define LOOKUP_NO_SYMLINKS 0x010000 /* No symlink crossing. */ #define LOOKUP_NO_MAGICLINKS 0x020000 /* No nd_jump_link() crossing. */ +#define LOOKUP_NO_XDEV 0x040000 /* No mountpoint crossing. */ extern int path_pts(struct path *path); -- 2.24.0
WARNING: multiple messages have this Message-ID (diff)
From: Aleksa Sarai <cyphar@cyphar.com> To: Al Viro <viro@zeniv.linux.org.uk>, 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>, Alexei Starovoitov <ast@kernel.org>, Daniel Borkmann <daniel@iogearbox.net>, Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>, Jonathan Corbet <corbet@lwn.net> Cc: Aleksa Sarai <cyphar@cyphar.com>, Christian Brauner <christian.brauner@ubuntu.com>, David Drysdale <drysdale@google.com>, Andy Lutomirski <luto@kernel.org>, Linus Torvalds <torvalds@linux-foundation.org>, Eric Biederman <ebiederm@xmission.com>, Andrew Morton <akpm@linux-foundation.org>, Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>, Tycho Andersen <tycho@tycho.ws>, 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>, dev@opencontainers.org, containers@lists.linux-foundation.org, bpf@vger.kernel.org, netdev@vger.kernel.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-doc@vger.kernel.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: [PATCH v17 07/13] namei: LOOKUP_NO_XDEV: block mountpoint crossing Date: Sun, 17 Nov 2019 12:17:07 +1100 [thread overview] Message-ID: <20191117011713.13032-8-cyphar@cyphar.com> (raw) Message-ID: <20191117011707.ZzSFdz3LbB1M9EoXAwG7iYr4oh1WQBsTewWedFMVn6E@z> (raw) In-Reply-To: <20191117011713.13032-1-cyphar@cyphar.com> /* Background. */ The need to contain path operations within a mountpoint has been a long-standing usecase that userspace has historically implemented manually with liberal usage of stat(). find, rsync, tar and many other programs implement these semantics -- but it'd be much simpler to have a fool-proof way of refusing to open a path if it crosses a mountpoint. This is part of a refresh of Al's AT_NO_JUMPS patchset[1] (which was a variation on David Drysdale's O_BENEATH patchset[2], which in turn was based on the Capsicum project[3]). /* Userspace API. */ LOOKUP_NO_XDEV will be exposed to userspace through openat2(2). /* Semantics. */ Unlike most other LOOKUP flags (most notably LOOKUP_FOLLOW), LOOKUP_NO_XDEV applies to all components of the path. With LOOKUP_NO_XDEV, any path component which crosses a mount-point during path resolution (including "..") will yield an -EXDEV. Absolute paths, absolute symlinks, and magic-links will only yield an -EXDEV if the jump involved changing mount-points. /* Testing. */ LOOKUP_NO_XDEV is tested as part of the openat2(2) selftests. [1]: https://lore.kernel.org/lkml/20170429220414.GT29622@ZenIV.linux.org.uk/ [2]: https://lore.kernel.org/lkml/1415094884-18349-1-git-send-email-drysdale@google.com/ [3]: https://lore.kernel.org/lkml/1404124096-21445-1-git-send-email-drysdale@google.com/ Cc: Christian Brauner <christian.brauner@ubuntu.com> Suggested-by: David Drysdale <drysdale@google.com> Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Suggested-by: Andy Lutomirski <luto@kernel.org> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Aleksa Sarai <cyphar@cyphar.com> --- fs/namei.c | 31 +++++++++++++++++++++++++++---- include/linux/namei.h | 1 + 2 files changed, 28 insertions(+), 4 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 415a897729c8..321c8ad5d6b3 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -838,6 +838,11 @@ static inline void path_to_nameidata(const struct path *path, static int nd_jump_root(struct nameidata *nd) { + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + /* Absolute path arguments to path_init() are allowed. */ + if (nd->path.mnt != NULL && nd->path.mnt != nd->root.mnt) + return -EXDEV; + } if (!nd->root.mnt) { int error = set_root(nd); if (error) @@ -873,6 +878,12 @@ int nd_jump_link(struct path *path) if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS)) goto err; + error = -EXDEV; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) { + if (nd->path.mnt != path->mnt) + goto err; + } + path_put(&nd->path); nd->path = *path; nd->inode = nd->path.dentry->d_inode; @@ -1280,12 +1291,16 @@ static int follow_managed(struct path *path, struct nameidata *nd) break; } - if (need_mntput && path->mnt == mnt) - mntput(path->mnt); + if (need_mntput) { + if (path->mnt == mnt) + mntput(path->mnt); + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + ret = -EXDEV; + else + nd->flags |= LOOKUP_JUMPED; + } if (ret == -EISDIR || !ret) ret = 1; - if (need_mntput) - nd->flags |= LOOKUP_JUMPED; if (unlikely(ret < 0)) path_put_conditional(path, nd); return ret; @@ -1342,6 +1357,8 @@ static bool __follow_mount_rcu(struct nameidata *nd, struct path *path, mounted = __lookup_mnt(path->mnt, path->dentry); if (!mounted) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return false; path->mnt = &mounted->mnt; path->dentry = mounted->mnt.mnt_root; nd->flags |= LOOKUP_JUMPED; @@ -1388,6 +1405,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (&mparent->mnt == nd->path.mnt) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -ECHILD; /* we know that mountpoint was pinned */ nd->path.dentry = mountpoint; nd->path.mnt = &mparent->mnt; @@ -1402,6 +1421,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) return -ECHILD; if (!mounted) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -ECHILD; nd->path.mnt = &mounted->mnt; nd->path.dentry = mounted->mnt.mnt_root; inode = nd->path.dentry->d_inode; @@ -1500,6 +1521,8 @@ static int follow_dotdot(struct nameidata *nd) } if (!follow_up(&nd->path)) break; + if (unlikely(nd->flags & LOOKUP_NO_XDEV)) + return -EXDEV; } follow_mount(&nd->path); nd->inode = nd->path.dentry->d_inode; diff --git a/include/linux/namei.h b/include/linux/namei.h index 1573b8493d98..25ee88c4acb1 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -42,6 +42,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; /* Scoping flags for lookup. */ #define LOOKUP_NO_SYMLINKS 0x010000 /* No symlink crossing. */ #define LOOKUP_NO_MAGICLINKS 0x020000 /* No nd_jump_link() crossing. */ +#define LOOKUP_NO_XDEV 0x040000 /* No mountpoint crossing. */ extern int path_pts(struct path *path); -- 2.24.0
next prev parent reply other threads:[~2019-11-17 1:35 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-11-17 1:17 [PATCH v17 00/13] open: introduce openat2(2) syscall Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 01/13] namei: only return -ECHILD from follow_dotdot_rcu() Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 02/13] nsfs: clean-up ns_get_path() signature to return int Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 03/13] namei: allow nd_jump_link() to produce errors Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 04/13] namei: allow set_root() " Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 05/13] namei: LOOKUP_NO_SYMLINKS: block symlink resolution Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 06/13] namei: LOOKUP_NO_MAGICLINKS: block magic-link resolution Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai [this message] 2019-11-17 1:17 ` [PATCH v17 07/13] namei: LOOKUP_NO_XDEV: block mountpoint crossing Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 08/13] namei: LOOKUP_BENEATH: O_BENEATH-like scoped resolution Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-25 0:26 ` Al Viro 2019-11-25 6:03 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 09/13] namei: LOOKUP_IN_ROOT: chroot-like " Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 10/13] namei: LOOKUP_{IN_ROOT, BENEATH}: permit limited ".." resolution Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 10/13] namei: LOOKUP_{IN_ROOT,BENEATH}: " Aleksa Sarai 2019-11-25 0:35 ` Al Viro 2019-11-25 13:21 ` Aleksa Sarai 2019-11-28 10:10 ` Aleksa Sarai 2019-11-17 1:17 ` [PATCH v17 11/13] open: introduce openat2(2) syscall Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-25 0:37 ` Al Viro 2019-11-17 1:17 ` [PATCH v17 12/13] selftests: add openat2(2) selftests Aleksa Sarai 2019-11-17 1:17 ` Aleksa Sarai 2019-11-17 1:28 ` [PATCH v17 13/13] Documentation: path-lookup: include new LOOKUP flags Aleksa Sarai 2019-11-17 1:28 ` Aleksa Sarai 2019-11-25 0:39 ` [PATCH v17 00/13] open: introduce openat2(2) syscall Al Viro
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --in-reply-to=20191117011713.13032-8-cyphar@cyphar.com \ --to=cyphar@cyphar.com \ --cc=akpm@linux-foundation.org \ --cc=alexander.shishkin@linux.intel.com \ --cc=andriin@fb.com \ --cc=arnd@arndb.de \ --cc=asarai@suse.de \ --cc=ast@kernel.org \ --cc=bfields@fieldses.org \ --cc=bpf@vger.kernel.org \ --cc=chanho.min@lge.com \ --cc=christian.brauner@ubuntu.com \ --cc=christian@brauner.io \ --cc=containers@lists.linux-foundation.org \ --cc=corbet@lwn.net \ --cc=daniel@iogearbox.net \ --cc=dev@opencontainers.org \ --cc=dhowells@redhat.com \ --cc=drysdale@google.com \ --cc=ebiederm@xmission.com \ --cc=jannh@google.com \ --cc=jlayton@kernel.org \ --cc=jolsa@redhat.com \ --cc=kafai@fb.com \ --cc=keescook@chromium.org \ --cc=libc-alpha@sourceware.org \ --cc=linux-alpha@vger.kernel.org \ --cc=linux-api@vger.kernel.org \ --cc=linux-arch@vger.kernel.org \ --cc=linux-arm-kernel@lists.infradead.org \ --cc=linux-doc@vger.kernel.org \ --cc=linux-fsdevel@vger.kernel.org \ --cc=linux-ia64@vger.kernel.org \ --cc=linux-kernel@vger.kernel.org \ --cc=linux-kselftest@vger.kernel.org \ --cc=linux-m68k@lists.linux-m68k.org \ --cc=linux-mips@vger.kernel.org \ --cc=linux-parisc@vger.kernel.org \ --cc=linux-s390@vger.kernel.org \ --cc=linux-sh@vger.kernel.org \ --cc=linux-xtensa@linux-xtensa.org \ --cc=linux@rasmusvillemoes.dk \ --cc=linuxppc-dev@lists.ozlabs.org \ --cc=luto@kernel.org \ --cc=mingo@redhat.com \ --cc=namhyung@kernel.org \ --cc=netdev@vger.kernel.org \ --cc=oleg@redhat.com \ --cc=peterz@infradead.org \ --cc=shuah@kernel.org \ --cc=skhan@linuxfoundation.org \ --cc=songliubraving@fb.com \ --cc=sparclinux@vger.kernel.org \ --cc=torvalds@linux-foundation.org \ --cc=tycho@tycho.ws \ --cc=viro@zeniv.linux.org.uk \ --cc=yhs@fb.com \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: linkBe sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for NNTP newsgroup(s).