Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752743AbaKDJzO (ORCPT ); Tue, 4 Nov 2014 04:55:14 -0500 Received: from mail-wg0-f73.google.com ([74.125.82.73]:33347 "EHLO mail-wg0-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752697AbaKDJzB (ORCPT ); Tue, 4 Nov 2014 04:55:01 -0500 From: David Drysdale To: linux-kernel@vger.kernel.org, Alexander Viro , Kees Cook , "Eric W. Biederman" Cc: Greg Kroah-Hartman , Meredydd Luff , Will Drewry , Jorge Lucangeli Obes , Ricky Zhou , Lee Campbell , Julien Tinnes , Mike Depinet , James Morris , Andy Lutomirski , Paolo Bonzini , Paul Moore , Christoph Hellwig , linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, David Drysdale Subject: [PATCHv2 1/3] fs: add O_BENEATH flag to openat(2) Date: Tue, 4 Nov 2014 09:54:42 +0000 Message-Id: <1415094884-18349-2-git-send-email-drysdale@google.com> X-Mailer: git-send-email 2.1.0.rc2.206.gedb03e5 In-Reply-To: <1415094884-18349-1-git-send-email-drysdale@google.com> References: <1415094884-18349-1-git-send-email-drysdale@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Add a new O_BENEATH flag for openat(2) which restricts the provided path, rejecting (with -EACCES) paths that are not beneath the provided dfd. In particular, reject: - paths that contain .. components - paths that begin with / - symlinks that have paths as above. Also disallow use of nd_jump_link() for following symlinks without path expansion, when O_BENEATH is set. Signed-off-by: David Drysdale --- arch/alpha/include/uapi/asm/fcntl.h | 1 + arch/parisc/include/uapi/asm/fcntl.h | 1 + arch/sparc/include/uapi/asm/fcntl.h | 1 + fs/fcntl.c | 5 +++-- fs/namei.c | 21 ++++++++++++++++++--- fs/open.c | 4 +++- fs/proc/base.c | 4 +++- fs/proc/namespaces.c | 7 ++++++- include/linux/namei.h | 3 ++- include/uapi/asm-generic/fcntl.h | 4 ++++ 10 files changed, 42 insertions(+), 9 deletions(-) diff --git a/arch/alpha/include/uapi/asm/fcntl.h b/arch/alpha/include/uapi/asm/fcntl.h index 09f49a6b87d1..76a87038d2c1 100644 --- a/arch/alpha/include/uapi/asm/fcntl.h +++ b/arch/alpha/include/uapi/asm/fcntl.h @@ -33,6 +33,7 @@ #define O_PATH 040000000 #define __O_TMPFILE 0100000000 +#define O_BENEATH 0200000000 /* no / or .. in openat path */ #define F_GETLK 7 #define F_SETLK 8 diff --git a/arch/parisc/include/uapi/asm/fcntl.h b/arch/parisc/include/uapi/asm/fcntl.h index 34a46cbc76ed..3adadf72f929 100644 --- a/arch/parisc/include/uapi/asm/fcntl.h +++ b/arch/parisc/include/uapi/asm/fcntl.h @@ -21,6 +21,7 @@ #define O_PATH 020000000 #define __O_TMPFILE 040000000 +#define O_BENEATH 080000000 /* no / or .. in openat path */ #define F_GETLK64 8 #define F_SETLK64 9 diff --git a/arch/sparc/include/uapi/asm/fcntl.h b/arch/sparc/include/uapi/asm/fcntl.h index 7e8ace5bf760..ea38f0bd6cec 100644 --- a/arch/sparc/include/uapi/asm/fcntl.h +++ b/arch/sparc/include/uapi/asm/fcntl.h @@ -36,6 +36,7 @@ #define O_PATH 0x1000000 #define __O_TMPFILE 0x2000000 +#define O_BENEATH 0x4000000 /* no / or .. in openat path */ #define F_GETOWN 5 /* for sockets. */ #define F_SETOWN 6 /* for sockets. */ diff --git a/fs/fcntl.c b/fs/fcntl.c index 22d1c3df61ac..c07a32efc34b 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -747,14 +747,15 @@ static int __init fcntl_init(void) * Exceptions: O_NONBLOCK is a two bit define on parisc; O_NDELAY * is defined as O_NONBLOCK on some platforms and not on others. */ - BUILD_BUG_ON(20 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( + BUILD_BUG_ON(21 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32( O_RDONLY | O_WRONLY | O_RDWR | O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC | O_APPEND | /* O_NONBLOCK | */ __O_SYNC | O_DSYNC | FASYNC | O_DIRECT | O_LARGEFILE | O_DIRECTORY | O_NOFOLLOW | O_NOATIME | O_CLOEXEC | - __FMODE_EXEC | O_PATH | __O_TMPFILE + __FMODE_EXEC | O_PATH | __O_TMPFILE | + O_BENEATH )); fasync_cache = kmem_cache_create("fasync_cache", diff --git a/fs/namei.c b/fs/namei.c index a7b05bf82d31..01d1d97eab3e 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -685,13 +685,16 @@ static inline void path_to_nameidata(const struct path *path, * Helper to directly jump to a known parsed path from ->follow_link, * caller must have taken a reference to path beforehand. */ -void nd_jump_link(struct nameidata *nd, struct path *path) +int nd_jump_link(struct nameidata *nd, struct path *path) { + if (nd->flags & LOOKUP_BENEATH) + return -EPERM; path_put(&nd->path); nd->path = *path; nd->inode = nd->path.dentry->d_inode; nd->flags |= LOOKUP_JUMPED; + return 0; } static inline void put_link(struct nameidata *nd, struct path *link, void *cookie) @@ -1743,9 +1746,14 @@ static int link_path_walk(const char *name, struct nameidata *nd) { struct path next; int err; - - while (*name=='/') + + while (*name == '/') { + if (nd->flags & LOOKUP_BENEATH) { + err = -EPERM; + goto exit; + } name++; + } if (!*name) return 0; @@ -1764,6 +1772,10 @@ static int link_path_walk(const char *name, struct nameidata *nd) if (name[0] == '.') switch (hashlen_len(hash_len)) { case 2: if (name[1] == '.') { + if (nd->flags & LOOKUP_BENEATH) { + err = -EPERM; + goto exit; + } type = LAST_DOTDOT; nd->flags |= LOOKUP_JUMPED; } @@ -1815,6 +1827,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) break; } } +exit: terminate_walk(nd); return err; } @@ -1853,6 +1866,8 @@ static int path_init(int dfd, const char *name, unsigned int flags, nd->m_seq = read_seqbegin(&mount_lock); if (*name=='/') { + if (flags & LOOKUP_BENEATH) + return -EPERM; if (flags & LOOKUP_RCU) { rcu_read_lock(); nd->seq = set_root_rcu(nd); diff --git a/fs/open.c b/fs/open.c index d6fd3acde134..8afca5b87a0b 100644 --- a/fs/open.c +++ b/fs/open.c @@ -874,7 +874,7 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o * If we have O_PATH in the open flag. Then we * cannot have anything other than the below set of flags */ - flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH; + flags &= O_DIRECTORY | O_NOFOLLOW | O_PATH | O_BENEATH; acc_mode = 0; } else { acc_mode = MAY_OPEN | ACC_MODE(flags); @@ -905,6 +905,8 @@ static inline int build_open_flags(int flags, umode_t mode, struct open_flags *o lookup_flags |= LOOKUP_DIRECTORY; if (!(flags & O_NOFOLLOW)) lookup_flags |= LOOKUP_FOLLOW; + if (flags & O_BENEATH) + lookup_flags |= LOOKUP_BENEATH; op->lookup_flags = lookup_flags; return 0; } diff --git a/fs/proc/base.c b/fs/proc/base.c index baf852b648ad..75d430155f9a 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1410,7 +1410,9 @@ static void *proc_pid_follow_link(struct dentry *dentry, struct nameidata *nd) if (error) goto out; - nd_jump_link(nd, &path); + error = nd_jump_link(nd, &path); + if (error) + goto out; return NULL; out: return ERR_PTR(error); diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c index 89026095f2b5..5cdbe5950756 100644 --- a/fs/proc/namespaces.c +++ b/fs/proc/namespaces.c @@ -113,6 +113,7 @@ static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd) struct proc_inode *ei = PROC_I(inode); struct task_struct *task; struct path ns_path; + int err; void *error = ERR_PTR(-EACCES); task = get_proc_task(inode); @@ -129,7 +130,11 @@ static void *proc_ns_follow_link(struct dentry *dentry, struct nameidata *nd) } ns_path.mnt = mntget(nd->path.mnt); - nd_jump_link(nd, &ns_path); + err = nd_jump_link(nd, &ns_path); + if (err) { + error = ERR_PTR(err); + goto out_put_task; + } error = NULL; out_put_task: diff --git a/include/linux/namei.h b/include/linux/namei.h index 492de72560fa..a018cd8219ec 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -39,6 +39,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; #define LOOKUP_FOLLOW 0x0001 #define LOOKUP_DIRECTORY 0x0002 #define LOOKUP_AUTOMOUNT 0x0004 +#define LOOKUP_BENEATH 0x0008 #define LOOKUP_PARENT 0x0010 #define LOOKUP_REVAL 0x0020 @@ -81,7 +82,7 @@ extern int follow_up(struct path *); extern struct dentry *lock_rename(struct dentry *, struct dentry *); extern void unlock_rename(struct dentry *, struct dentry *); -extern void nd_jump_link(struct nameidata *nd, struct path *path); +extern int nd_jump_link(struct nameidata *nd, struct path *path); static inline void nd_set_link(struct nameidata *nd, char *path) { diff --git a/include/uapi/asm-generic/fcntl.h b/include/uapi/asm-generic/fcntl.h index 7543b3e51331..f63aa749a4fb 100644 --- a/include/uapi/asm-generic/fcntl.h +++ b/include/uapi/asm-generic/fcntl.h @@ -92,6 +92,10 @@ #define O_TMPFILE (__O_TMPFILE | O_DIRECTORY) #define O_TMPFILE_MASK (__O_TMPFILE | O_DIRECTORY | O_CREAT) +#ifndef O_BENEATH +#define O_BENEATH 040000000 /* no / or .. in openat path */ +#endif + #ifndef O_NDELAY #define O_NDELAY O_NONBLOCK #endif -- 2.1.0.rc2.206.gedb03e5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/