@@ -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
@@ -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
@@ -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. */
@@ -740,7 +740,7 @@ 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(21 - 1 /* for O_RDONLY being 0 */ != HWEIGHT32(
+ BUILD_BUG_ON(22 - 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 | */
@@ -748,7 +748,7 @@ static int __init fcntl_init(void)
O_DIRECT | O_LARGEFILE | O_DIRECTORY |
O_NOFOLLOW | O_NOATIME | O_CLOEXEC |
__FMODE_EXEC | O_PATH | __O_TMPFILE |
- __FMODE_NONOTIFY
+ __FMODE_NONOTIFY| O_BENEATH
));
fasync_cache = kmem_cache_create("fasync_cache",
@@ -827,14 +827,18 @@ 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 path *path)
+int nd_jump_link(struct path *path)
{
struct nameidata *nd = current->nameidata;
+
+ 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)
@@ -1000,6 +1004,8 @@ const char *get_link(struct nameidata *nd)
}
}
if (*res == '/') {
+ if (nd->flags & LOOKUP_BENEATH)
+ return ERR_PTR(-EPERM);
if (nd->flags & LOOKUP_RCU) {
struct dentry *d;
if (!nd->root.mnt)
@@ -1888,6 +1894,8 @@ 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)
+ return -EPERM;
type = LAST_DOTDOT;
nd->flags |= LOOKUP_JUMPED;
}
@@ -2000,6 +2008,8 @@ static const char *path_init(struct nameidata *nd, unsigned flags)
nd->m_seq = read_seqbegin(&mount_lock);
if (*s == '/') {
+ if (flags & LOOKUP_BENEATH)
+ return ERR_PTR(-EPERM);
if (flags & LOOKUP_RCU) {
rcu_read_lock();
set_root_rcu(nd);
@@ -917,7 +917,7 @@ 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);
@@ -948,6 +948,8 @@ 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;
}
@@ -1589,7 +1589,9 @@ static const char *proc_pid_follow_link(struct dentry *dentry, void **cookie)
if (error)
goto out;
- nd_jump_link(&path);
+ error = nd_jump_link(&path);
+ if (error)
+ goto out;
return NULL;
out:
return ERR_PTR(error);
@@ -36,6 +36,7 @@ static const char *proc_ns_follow_link(struct dentry *dentry, void **cookie)
const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops;
struct task_struct *task;
struct path ns_path;
+ int err;
void *error = ERR_PTR(-EACCES);
task = get_proc_task(inode);
@@ -44,8 +45,11 @@ static const char *proc_ns_follow_link(struct dentry *dentry, void **cookie)
if (ptrace_may_access(task, PTRACE_MODE_READ)) {
error = ns_get_path(&ns_path, task, ns_ops);
- if (!error)
- nd_jump_link(&ns_path);
+ if (!error) {
+ err = nd_jump_link(&ns_path);
+ if (err)
+ error = ERR_PTR(err);
+ }
}
put_task_struct(task);
return error;
@@ -27,6 +27,7 @@ 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
@@ -85,7 +86,7 @@ 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 path *path);
+extern int nd_jump_link(struct path *path);
static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
{
@@ -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
Add a new O_BENEATH flag for openat(2) which restricts the provided path, rejecting (with -EPERM) 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 <drysdale@google.com> --- 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 | 4 ++-- fs/namei.c | 12 +++++++++++- fs/open.c | 4 +++- fs/proc/base.c | 4 +++- fs/proc/namespaces.c | 8 ++++++-- include/linux/namei.h | 3 ++- include/uapi/asm-generic/fcntl.h | 4 ++++ 10 files changed, 34 insertions(+), 8 deletions(-)