The patch titled
readlinkat: ensure we return ENOENT for the empty pathname for normal lookups
has been added to the -mm tree. Its filename is
readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
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out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: readlinkat: ensure we return ENOENT for the empty pathname for normal lookups
From: Andy Whitcroft <apw@xxxxxxxxxxxxx>
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 <viro@xxxxxxxxxxxxxxxxxx>
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.
BugLink: http://bugs.launchpad.net/bugs/817187
Signed-off-by: Andy Whitcroft <apw@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namei.c | 24 +++++++++++++++++++-----
fs/stat.c | 5 +++--
include/linux/namei.h | 1 +
3 files changed, 23 insertions(+), 7 deletions(-)
diff -puN fs/namei.c~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups fs/namei.c
--- a/fs/namei.c~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups
+++ a/fs/namei.c
@@ -137,7 +137,8 @@ static int do_getname(const char __user
return retval;
}
-static char *getname_flags(const char __user * filename, int flags)
+static char *getname_flags_empty(const char __user * filename,
+ int flags, int *empty)
{
char *tmp, *result;
@@ -148,6 +149,8 @@ static char *getname_flags(const char __
result = tmp;
if (retval < 0) {
+ if (retval == -ENOENT && empty)
+ *empty = 1;
if (retval != -ENOENT || !(flags & LOOKUP_EMPTY)) {
__putname(tmp);
result = ERR_PTR(retval);
@@ -158,9 +161,14 @@ static char *getname_flags(const char __
return result;
}
+static char *getname_flags(const char __user * filename, int flags)
+{
+ return getname_flags_empty(filename, flags, 0);
+}
+
char *getname(const char __user * filename)
{
- return getname_flags(filename, 0);
+ return getname_flags_empty(filename, 0, 0);
}
#ifdef CONFIG_AUDITSYSCALL
@@ -1807,11 +1815,11 @@ struct dentry *lookup_one_len(const char
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_empty(name, flags, empty);
int err = PTR_ERR(tmp);
if (!IS_ERR(tmp)) {
@@ -1825,6 +1833,12 @@ int user_path_at(int dfd, const char __u
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 -puN fs/stat.c~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups fs/stat.c
--- a/fs/stat.c~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups
+++ a/fs/stat.c
@@ -296,15 +296,16 @@ SYSCALL_DEFINE4(readlinkat, int, dfd, co
{
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 -puN include/linux/namei.h~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups include/linux/namei.h
--- a/include/linux/namei.h~readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups
+++ a/include/linux/namei.h
@@ -66,6 +66,7 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LA
#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)
_
Patches currently in -mm which might be from apw@xxxxxxxxxxxxx are
readlinkat-ensure-we-return-enoent-for-the-empty-pathname-for-normal-lookups.patch
--
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