Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752024AbaKCL4J (ORCPT ); Mon, 3 Nov 2014 06:56:09 -0500 Received: from mail-lb0-f202.google.com ([209.85.217.202]:42115 "EHLO mail-lb0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751820AbaKCL4D (ORCPT ); Mon, 3 Nov 2014 06:56:03 -0500 From: David Drysdale To: linux-kernel@vger.kernel.org, Alexander Viro , Kees Cook 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 , "Eric W. Biederman" , linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, David Drysdale Subject: [PATCH 1/3] fs: add O_BENEATH flag to openat(2) Date: Mon, 3 Nov 2014 11:48:23 +0000 Message-Id: <1415015305-15494-2-git-send-email-drysdale@google.com> X-Mailer: git-send-email 2.1.0.rc2.206.gedb03e5 In-Reply-To: <1415015305-15494-1-git-send-email-drysdale@google.com> References: <1415015305-15494-1-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. 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 | 43 ++++++++++++++++++++++++------------ fs/open.c | 4 +++- include/linux/namei.h | 1 + include/uapi/asm-generic/fcntl.h | 4 ++++ 8 files changed, 43 insertions(+), 17 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..2fd547014b6b 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -647,7 +647,7 @@ static __always_inline void set_root(struct nameidata *nd) get_fs_root(current->fs, &nd->root); } -static int link_path_walk(const char *, struct nameidata *); +static int link_path_walk(const char *, struct nameidata *, unsigned int); static __always_inline unsigned set_root_rcu(struct nameidata *nd) { @@ -819,7 +819,8 @@ static int may_linkat(struct path *link) } static __always_inline int -follow_link(struct path *link, struct nameidata *nd, void **p) +follow_link(struct path *link, struct nameidata *nd, unsigned int flags, + void **p) { struct dentry *dentry = link->dentry; int error; @@ -867,7 +868,7 @@ follow_link(struct path *link, struct nameidata *nd, void **p) nd->flags |= LOOKUP_JUMPED; } nd->inode = nd->path.dentry->d_inode; - error = link_path_walk(s, nd); + error = link_path_walk(s, nd, flags); if (unlikely(error)) put_link(nd, link, *p); } @@ -1585,7 +1586,8 @@ out_err: * Without that kind of total limit, nasty chains of consecutive * symlinks can cause almost arbitrarily long lookups. */ -static inline int nested_symlink(struct path *path, struct nameidata *nd) +static inline int nested_symlink(struct path *path, struct nameidata *nd, + unsigned int flags) { int res; @@ -1603,7 +1605,7 @@ static inline int nested_symlink(struct path *path, struct nameidata *nd) struct path link = *path; void *cookie; - res = follow_link(&link, nd, &cookie); + res = follow_link(&link, nd, flags, &cookie); if (res) break; res = walk_component(nd, path, LOOKUP_FOLLOW); @@ -1739,13 +1741,19 @@ static inline u64 hash_name(const char *name) * Returns 0 and nd will have valid dentry and mnt on success. * Returns error and drops reference to input namei data on failure. */ -static int link_path_walk(const char *name, struct nameidata *nd) +static int link_path_walk(const char *name, struct nameidata *nd, + unsigned int flags) { struct path next; int err; - while (*name=='/') + while (*name == '/') { + if (flags & LOOKUP_BENEATH) { + err = -EACCES; + 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 (flags & LOOKUP_BENEATH) { + err = -EACCES; + goto exit; + } type = LAST_DOTDOT; nd->flags |= LOOKUP_JUMPED; } @@ -1806,7 +1818,7 @@ static int link_path_walk(const char *name, struct nameidata *nd) return err; if (err) { - err = nested_symlink(&next, nd); + err = nested_symlink(&next, nd, flags); if (err) return err; } @@ -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 -EACCES; if (flags & LOOKUP_RCU) { rcu_read_lock(); nd->seq = set_root_rcu(nd); @@ -1953,7 +1968,7 @@ static int path_lookupat(int dfd, const char *name, return err; current->total_link_count = 0; - err = link_path_walk(name, nd); + err = link_path_walk(name, nd, flags); if (!err && !(flags & LOOKUP_PARENT)) { err = lookup_last(nd, &path); @@ -1964,7 +1979,7 @@ static int path_lookupat(int dfd, const char *name, if (unlikely(err)) break; nd->flags |= LOOKUP_PARENT; - err = follow_link(&link, nd, &cookie); + err = follow_link(&link, nd, flags, &cookie); if (err) break; err = lookup_last(nd, &path); @@ -2304,7 +2319,7 @@ path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags return err; current->total_link_count = 0; - err = link_path_walk(name, &nd); + err = link_path_walk(name, &nd, flags); if (err) goto out; @@ -2316,7 +2331,7 @@ path_mountpoint(int dfd, const char *name, struct path *path, unsigned int flags if (unlikely(err)) break; nd.flags |= LOOKUP_PARENT; - err = follow_link(&link, &nd, &cookie); + err = follow_link(&link, &nd, flags, &cookie); if (err) break; err = mountpoint_last(&nd, path); @@ -3202,7 +3217,7 @@ static struct file *path_openat(int dfd, struct filename *pathname, goto out; current->total_link_count = 0; - error = link_path_walk(pathname->name, nd); + error = link_path_walk(pathname->name, nd, flags); if (unlikely(error)) goto out; @@ -3221,7 +3236,7 @@ static struct file *path_openat(int dfd, struct filename *pathname, break; nd->flags |= LOOKUP_PARENT; nd->flags &= ~(LOOKUP_OPEN|LOOKUP_CREATE|LOOKUP_EXCL); - error = follow_link(&link, nd, &cookie); + error = follow_link(&link, nd, flags, &cookie); if (unlikely(error)) break; error = do_last(nd, &path, file, op, &opened, pathname); 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/include/linux/namei.h b/include/linux/namei.h index 492de72560fa..bd0615d1143b 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 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/