From 1fa1e7f615f4d3ae436fa319af6e4eebdd4026a8 Mon Sep 17 00:00:00 2001 From: Andy Whitcroft Date: Wed, 2 Nov 2011 09:44:39 +0100 Subject: [PATCH] readlinkat: ensure we return ENOENT for the empty pathname for normal lookups Since the commit below which added O_PATH support to the *at() calls, the error return for readlink/readlinkat for the empty pathname has switched from ENOENT to EINVAL: commit 65cfc6722361570bfe255698d9cd4dccaf47570d Author: Al Viro Date: Sun Mar 13 15:56:26 2011 -0400 readlinkat(), fchownat() and fstatat() with empty relative pathnames This is both unexpected for userspace and makes readlink/readlinkat inconsistant with all other interfaces; and inconsistant with our stated return for these pathnames. As the readlinkat call does not have a flags parameter we cannot use the AT_EMPTY_PATH approach used in the other calls. Therefore expose whether the original path is infact entry via a new user_path_at_empty() path lookup function. Use this to determine whether to default to EINVAL or ENOENT for failures. Addresses http://bugs.launchpad.net/bugs/817187 [akpm@linux-foundation.org: remove unused getname_flags()] Signed-off-by: Andy Whitcroft Cc: Christoph Hellwig Cc: Al Viro Cc: Cc: Signed-off-by: Andrew Morton Signed-off-by: Christoph Hellwig --- fs/namei.c | 18 +++++++++++++----- fs/stat.c | 5 +++-- include/linux/namei.h | 1 + 3 files changed, 17 insertions(+), 7 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index 7657be4352b..ac6d214da82 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -137,7 +137,7 @@ static int do_getname(const char __user *filename, char *page) return retval; } -static char *getname_flags(const char __user * filename, int flags) +static char *getname_flags(const char __user *filename, int flags, int *empty) { char *tmp, *result; @@ -148,6 +148,8 @@ static char *getname_flags(const char __user * filename, int flags) result = tmp; if (retval < 0) { + if (retval == -ENOENT && empty) + *empty = 1; if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) { __putname(tmp); result = ERR_PTR(retval); @@ -160,7 +162,7 @@ static char *getname_flags(const char __user * filename, int flags) char *getname(const char __user * filename) { - return getname_flags(filename, 0); + return getname_flags(filename, 0, 0); } #ifdef CONFIG_AUDITSYSCALL @@ -1798,11 +1800,11 @@ struct dentry *lookup_one_len(const char *name, struct dentry *base, int len) return __lookup_hash(&this, base, NULL); } -int user_path_at(int dfd, const char __user *name, unsigned flags, - struct path *path) +int user_path_at_empty(int dfd, const char __user *name, unsigned flags, + struct path *path, int *empty) { struct nameidata nd; - char *tmp = getname_flags(name, flags); + char *tmp = getname_flags(name, flags, empty); int err = PTR_ERR(tmp); if (!IS_ERR(tmp)) { @@ -1816,6 +1818,12 @@ int user_path_at(int dfd, const char __user *name, unsigned flags, return err; } +int user_path_at(int dfd, const char __user *name, unsigned flags, + struct path *path) +{ + return user_path_at_empty(dfd, name, flags, path, 0); +} + static int user_path_parent(int dfd, const char __user *path, struct nameidata *nd, char **name) { diff --git a/fs/stat.c b/fs/stat.c index 78a3aa83c7e..8806b8997d2 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -294,15 +294,16 @@ SYSCALL_DEFINE4(readlinkat, int, dfd, const char __user *, pathname, { struct path path; int error; + int empty = 0; if (bufsiz <= 0) return -EINVAL; - error = user_path_at(dfd, pathname, LOOKUP_EMPTY, &path); + error = user_path_at_empty(dfd, pathname, LOOKUP_EMPTY, &path, &empty); if (!error) { struct inode *inode = path.dentry->d_inode; - error = -EINVAL; + error = empty ? -ENOENT : -EINVAL; if (inode->i_op->readlink) { error = security_inode_readlink(path.dentry); if (!error) { diff --git a/include/linux/namei.h b/include/linux/namei.h index 409328d1cbb..ffc02135c48 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -67,6 +67,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT, LAST_BIND}; #define LOOKUP_EMPTY 0x4000 extern int user_path_at(int, const char __user *, unsigned, struct path *); +extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty); #define user_path(name, path) user_path_at(AT_FDCWD, name, LOOKUP_FOLLOW, path) #define user_lpath(name, path) user_path_at(AT_FDCWD, name, 0, path)