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Subject[patch 1/3] [RFC] Change sys_readlink/sys_readlinkat buffer size parameter to size_t (POSIX mismatch)
man-page for readlink syscalls prototype with buffer size as type of size_t:
"ssize_t readlink(const char *path, char *buf, size_t bufsiz);"

Kernel readlink syscall interface has signed buffer size and doesn't match with
man-page described prototype.

POSIX and glibc implementation of the readlink interface have an unsigned buffer size.

This patch changes the syscall interface of sys_readlink and sys_readlinkat, by
changing the buffer size argument type to "size_t".

A buffer size of 0 will end in return value 0. This is _different_ behavior to
original sys_readlink/sys_readlinkat interface. But equal/similar to POSIXs one.


Signed-off-by: Daniel Gollub <dgollub@suse.de>


---

fs/9p/vfs_inode.c | 4 ++--
fs/bad_inode.c | 2 +-
fs/ecryptfs/inode.c | 2 +-
fs/gfs2/ops_inode.c | 2 +-
fs/hppfs/hppfs.c | 2 +-
fs/namei.c | 8 ++++----
fs/ocfs2/symlink.c | 2 +-
fs/proc/base.c | 6 +++---
fs/stat.c | 8 ++++----
include/linux/fs.h | 8 ++++----
include/linux/syscalls.h | 4 ++--
11 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/fs/9p/vfs_inode.c b/fs/9p/vfs_inode.c
index e83aa5e..dd70525 100644
--- a/fs/9p/vfs_inode.c
+++ b/fs/9p/vfs_inode.c
@@ -898,7 +898,7 @@ ino_t v9fs_qid2ino(struct p9_qid *qid)
*
*/

-static int v9fs_readlink(struct dentry *dentry, char *buffer, int buflen)
+static int v9fs_readlink(struct dentry *dentry, char *buffer, size_t buflen)
{
int retval;

@@ -952,7 +952,7 @@ done:
*/

static int v9fs_vfs_readlink(struct dentry *dentry, char __user * buffer,
- int buflen)
+ size_t buflen)
{
int retval;
int ret;
diff --git a/fs/bad_inode.c b/fs/bad_inode.c
index 5f1538c..5342a55 100644
--- a/fs/bad_inode.c
+++ b/fs/bad_inode.c
@@ -238,7 +238,7 @@ static int bad_inode_rename (struct inode *old_dir, struct dentry *old_dentry,
}

static int bad_inode_readlink(struct dentry *dentry, char __user *buffer,
- int buflen)
+ size_t buflen)
{
return -EIO;
}
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index 89209f0..378a1e2 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c
@@ -602,7 +602,7 @@ out_lock:
}

static int
-ecryptfs_readlink(struct dentry *dentry, char __user * buf, int bufsiz)
+ecryptfs_readlink(struct dentry *dentry, char __user * buf, size_t bufsiz)
{
int rc;
struct dentry *lower_dentry;
diff --git a/fs/gfs2/ops_inode.c b/fs/gfs2/ops_inode.c
index 534e1e2..8680062 100644
--- a/fs/gfs2/ops_inode.c
+++ b/fs/gfs2/ops_inode.c
@@ -894,7 +894,7 @@ out:
*/

static int gfs2_readlink(struct dentry *dentry, char __user *user_buf,
- int user_size)
+ size_t user_size)
{
struct gfs2_inode *ip = GFS2_I(dentry->d_inode);
char array[GFS2_FAST_NAME_SIZE], *buf = array;
diff --git a/fs/hppfs/hppfs.c b/fs/hppfs/hppfs.c
index 2b3d182..488f95d 100644
--- a/fs/hppfs/hppfs.c
+++ b/fs/hppfs/hppfs.c
@@ -637,7 +637,7 @@ static const struct super_operations hppfs_sbops = {
};

static int hppfs_readlink(struct dentry *dentry, char __user *buffer,
- int buflen)
+ size_t buflen)
{
struct dentry *proc_dentry;

diff --git a/fs/namei.c b/fs/namei.c
index 4ea63ed..63e01e4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2712,7 +2712,7 @@ asmlinkage long sys_rename(const char __user *oldname, const char __user *newnam
return sys_renameat(AT_FDCWD, oldname, AT_FDCWD, newname);
}

-int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const char *link)
+int vfs_readlink(struct dentry *dentry, char __user *buffer, size_t buflen, const char *link)
{
int len;

@@ -2721,7 +2721,7 @@ int vfs_readlink(struct dentry *dentry, char __user *buffer, int buflen, const c
goto out;

len = strlen(link);
- if (len > (unsigned) buflen)
+ if (len > buflen)
len = buflen;
if (copy_to_user(buffer, link, len))
len = -EFAULT;
@@ -2734,7 +2734,7 @@ out:
* have ->follow_link() touching nd only in nd_set_link(). Using (or not
* using) it for any given inode is up to filesystem.
*/
-int generic_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+int generic_readlink(struct dentry *dentry, char __user *buffer, size_t buflen)
{
struct nameidata nd;
void *cookie;
@@ -2768,7 +2768,7 @@ static char *page_getlink(struct dentry * dentry, struct page **ppage)
return kmap(page);
}

-int page_readlink(struct dentry *dentry, char __user *buffer, int buflen)
+int page_readlink(struct dentry *dentry, char __user *buffer, size_t buflen)
{
struct page *page = NULL;
char *s = page_getlink(dentry, &page);
diff --git a/fs/ocfs2/symlink.c b/fs/ocfs2/symlink.c
index cbd03df..3295ff7 100644
--- a/fs/ocfs2/symlink.c
+++ b/fs/ocfs2/symlink.c
@@ -101,7 +101,7 @@ bail:

static int ocfs2_readlink(struct dentry *dentry,
char __user *buffer,
- int buflen)
+ size_t buflen)
{
int ret;
char *link;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index b5918ae..14b90b9 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1333,7 +1333,7 @@ out:
return ERR_PTR(error);
}

-static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
+static int do_proc_readlink(struct path *path, char __user *buffer, size_t buflen)
{
char *tmp = (char*)__get_free_page(GFP_TEMPORARY);
char *pathname;
@@ -1357,7 +1357,7 @@ static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
return len;
}

-static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, int buflen)
+static int proc_pid_readlink(struct dentry * dentry, char __user * buffer, size_t buflen)
{
int error = -EACCES;
struct inode *inode = dentry->d_inode;
@@ -2246,7 +2246,7 @@ static const struct file_operations proc_coredump_filter_operations = {
* /proc/self:
*/
static int proc_self_readlink(struct dentry *dentry, char __user *buffer,
- int buflen)
+ size_t buflen)
{
struct pid_namespace *ns = dentry->d_sb->s_fs_info;
pid_t tgid = task_tgid_nr_ns(current, ns);
diff --git a/fs/stat.c b/fs/stat.c
index 7c46fbe..b521674 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -292,13 +292,13 @@ asmlinkage long sys_newfstat(unsigned int fd, struct stat __user *statbuf)
}

asmlinkage long sys_readlinkat(int dfd, const char __user *pathname,
- char __user *buf, int bufsiz)
+ char __user *buf, size_t bufsiz)
{
struct path path;
int error;

- if (bufsiz <= 0)
- return -EINVAL;
+ if (unlikely(!bufsiz))
+ return 0;

error = user_path_at(dfd, pathname, 0, &path);
if (!error) {
@@ -319,7 +319,7 @@ asmlinkage long sys_readlinkat(int dfd, const char __user *pathname,
}

asmlinkage long sys_readlink(const char __user *path, char __user *buf,
- int bufsiz)
+ size_t bufsiz)
{
return sys_readlinkat(AT_FDCWD, path, buf, bufsiz);
}
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a6a625b..816dc29 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1333,7 +1333,7 @@ struct inode_operations {
int (*mknod) (struct inode *,struct dentry *,int,dev_t);
int (*rename) (struct inode *, struct dentry *,
struct inode *, struct dentry *);
- int (*readlink) (struct dentry *, char __user *,int);
+ int (*readlink) (struct dentry *, char __user *,size_t);
void * (*follow_link) (struct dentry *, struct nameidata *);
void (*put_link) (struct dentry *, struct nameidata *, void *);
void (*truncate) (struct inode *);
@@ -2029,16 +2029,16 @@ extern const struct file_operations generic_ro_fops;

#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

-extern int vfs_readlink(struct dentry *, char __user *, int, const char *);
+extern int vfs_readlink(struct dentry *, char __user *, size_t, const char *);
extern int vfs_follow_link(struct nameidata *, const char *);
-extern int page_readlink(struct dentry *, char __user *, int);
+extern int page_readlink(struct dentry *, char __user *, size_t);
extern void *page_follow_link_light(struct dentry *, struct nameidata *);
extern void page_put_link(struct dentry *, struct nameidata *, void *);
extern int __page_symlink(struct inode *inode, const char *symname, int len,
gfp_t gfp_mask);
extern int page_symlink(struct inode *inode, const char *symname, int len);
extern const struct inode_operations page_symlink_inode_operations;
-extern int generic_readlink(struct dentry *, char __user *, int);
+extern int generic_readlink(struct dentry *, char __user *, size_t);
extern void generic_fillattr(struct inode *, struct kstat *);
extern int vfs_getattr(struct vfsmount *, struct dentry *, struct kstat *);
void inode_add_bytes(struct inode *inode, loff_t bytes);
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index d6ff145..e9582d1 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -326,7 +326,7 @@ asmlinkage ssize_t sys_sendfile(int out_fd, int in_fd,
asmlinkage ssize_t sys_sendfile64(int out_fd, int in_fd,
loff_t __user *offset, size_t count);
asmlinkage long sys_readlink(const char __user *path,
- char __user *buf, int bufsiz);
+ char __user *buf, size_t bufsiz);
asmlinkage long sys_creat(const char __user *pathname, int mode);
asmlinkage long sys_open(const char __user *filename,
int flags, int mode);
@@ -581,7 +581,7 @@ asmlinkage long sys_newfstatat(int dfd, char __user *filename,
asmlinkage long sys_fstatat64(int dfd, char __user *filename,
struct stat64 __user *statbuf, int flag);
asmlinkage long sys_readlinkat(int dfd, const char __user *path, char __user *buf,
- int bufsiz);
+ size_t bufsiz);
asmlinkage long sys_utimensat(int dfd, char __user *filename,
struct timespec __user *utimes, int flags);
asmlinkage long compat_sys_futimesat(unsigned int dfd, char __user *filename,


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