From patchwork Sat Nov 16 00:27:53 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Aleksa Sarai X-Patchwork-Id: 35970 Received: (qmail 22691 invoked by alias); 16 Nov 2019 00:29:56 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Delivered-To: mailing list libc-alpha@sourceware.org Received: (qmail 22683 invoked by uid 89); 16 Nov 2019 00:29:55 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-23.4 required=5.0 tests=AWL, BAYES_00, GIT_PATCH_0, GIT_PATCH_1, GIT_PATCH_2, GIT_PATCH_3, KAM_MANYTO, SPF_PASS autolearn=ham version=3.3.1 spammy= X-HELO: mout-p-202.mailbox.org From: Aleksa Sarai To: Al Viro , Jeff Layton , "J. Bruce Fields" , Arnd Bergmann , David Howells , Shuah Khan , Shuah Khan , Ingo Molnar , Peter Zijlstra , Alexei Starovoitov , Daniel Borkmann , Martin KaFai Lau , Song Liu , Yonghong Song , Andrii Nakryiko Cc: Aleksa Sarai , Eric Biederman , Andy Lutomirski , Andrew Morton , Kees Cook , Jann Horn , Tycho Andersen , David Drysdale , Chanho Min , Oleg Nesterov , Rasmus Villemoes , Alexander Shishkin , Jiri Olsa , Namhyung Kim , Christian Brauner , Aleksa Sarai , Linus Torvalds , 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-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 v16 03/12] namei: allow set_root() to produce errors Date: Sat, 16 Nov 2019 11:27:53 +1100 Message-Id: <20191116002802.6663-4-cyphar@cyphar.com> In-Reply-To: <20191116002802.6663-1-cyphar@cyphar.com> References: <20191116002802.6663-1-cyphar@cyphar.com> MIME-Version: 1.0 For LOOKUP_BENEATH and LOOKUP_IN_ROOT it is necessary to ensure that set_root() is never called, and thus (for hardening purposes) it should return an error rather than permit a breakout from the root. In addition, move all of the repetitive set_root() calls to nd_jump_root(). Signed-off-by: Aleksa Sarai --- fs/namei.c | 35 ++++++++++++++++++++++++----------- 1 file changed, 24 insertions(+), 11 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 965a25b2e3df..259652667881 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -798,7 +798,7 @@ static int complete_walk(struct nameidata *nd) return status; } -static void set_root(struct nameidata *nd) +static int set_root(struct nameidata *nd) { struct fs_struct *fs = current->fs; @@ -814,6 +814,7 @@ static void set_root(struct nameidata *nd) get_fs_root(fs, &nd->root); nd->flags |= LOOKUP_ROOT_GRABBED; } + return 0; } static void path_put_conditional(struct path *path, struct nameidata *nd) @@ -837,6 +838,11 @@ static inline void path_to_nameidata(const struct path *path, static int nd_jump_root(struct nameidata *nd) { + if (!nd->root.mnt) { + int error = set_root(nd); + if (error) + return error; + } if (nd->flags & LOOKUP_RCU) { struct dentry *d; nd->path = nd->root; @@ -1080,10 +1086,9 @@ const char *get_link(struct nameidata *nd) return res; } if (*res == '/') { - if (!nd->root.mnt) - set_root(nd); - if (unlikely(nd_jump_root(nd))) - return ERR_PTR(-ECHILD); + error = nd_jump_root(nd); + if (unlikely(error)) + return ERR_PTR(error); while (unlikely(*++res == '/')) ; } @@ -1698,8 +1703,13 @@ static inline int may_lookup(struct nameidata *nd) static inline int handle_dots(struct nameidata *nd, int type) { if (type == LAST_DOTDOT) { - if (!nd->root.mnt) - set_root(nd); + int error = 0; + + if (!nd->root.mnt) { + error = set_root(nd); + if (error) + return error; + } if (nd->flags & LOOKUP_RCU) { return follow_dotdot_rcu(nd); } else @@ -2162,6 +2172,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) /* must be paired with terminate_walk() */ static const char *path_init(struct nameidata *nd, unsigned flags) { + int error; const char *s = nd->name->name; if (!*s) @@ -2194,11 +2205,13 @@ static const char *path_init(struct nameidata *nd, unsigned flags) nd->path.dentry = NULL; nd->m_seq = read_seqbegin(&mount_lock); + + /* Figure out the starting path and root (if needed). */ if (*s == '/') { - set_root(nd); - if (likely(!nd_jump_root(nd))) - return s; - return ERR_PTR(-ECHILD); + error = nd_jump_root(nd); + if (unlikely(error)) + return ERR_PTR(error); + return s; } else if (nd->dfd == AT_FDCWD) { if (flags & LOOKUP_RCU) { struct fs_struct *fs = current->fs;