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vfs: show unreachable paths in getcwd and proc

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Prepend "(unreachable)" to path strings if the path is not reachable
from the current root.

Two places updated are
 - the return string from getcwd()
 - and symlinks under /proc/$PID.

Other uses of d_path() are left unchanged (we know that some old
software crashes if /proc/mounts is changed).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Miklos Szeredi 2010-08-10 11:41:41 +02:00 committed by Al Viro
parent ffd1f4ed5b
commit 8df9d1a414
4 changed files with 57 additions and 5 deletions
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54
fs/dcache.c
View File

@ -2019,6 +2019,11 @@ static int path_with_deleted(const struct path *path, struct path *root,
return prepend_path(path, root, buf, buflen);
}
static int prepend_unreachable(char **buffer, int *buflen)
{
return prepend(buffer, buflen, "(unreachable)", 13);
}
/**
* d_path - return the path of a dentry
* @path: path to report
@ -2064,6 +2069,39 @@ char *d_path(const struct path *path, char *buf, int buflen)
}
EXPORT_SYMBOL(d_path);
/**
* d_path_with_unreachable - return the path of a dentry
* @path: path to report
* @buf: buffer to return value in
* @buflen: buffer length
*
* The difference from d_path() is that this prepends "(unreachable)"
* to paths which are unreachable from the current process' root.
*/
char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
{
char *res = buf + buflen;
struct path root;
struct path tmp;
int error;
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
spin_lock(&dcache_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (!error && !path_equal(&tmp, &root))
error = prepend_unreachable(&res, &buflen);
spin_unlock(&dcache_lock);
path_put(&root);
if (error)
res = ERR_PTR(error);
return res;
}
/*
* Helper function for dentry_operations.d_dname() members
*/
@ -2173,15 +2211,23 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
char * cwd;
char *cwd = page + PAGE_SIZE;
int buflen = PAGE_SIZE;
cwd = __d_path(&pwd, &tmp, page, PAGE_SIZE);
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &tmp, &cwd, &buflen);
spin_unlock(&dcache_lock);
error = PTR_ERR(cwd);
if (IS_ERR(cwd))
if (error)
goto out;
/* Unreachable from current root */
if (!path_equal(&tmp, &root)) {
error = prepend_unreachable(&cwd, &buflen);
if (error)
goto out;
}
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
if (len <= size) {

2
fs/proc/base.c
View File

@ -1526,7 +1526,7 @@ static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
if (!tmp)
return -ENOMEM;
pathname = d_path(path, tmp, PAGE_SIZE);
pathname = d_path_with_unreachable(path, tmp, PAGE_SIZE);
len = PTR_ERR(pathname);
if (IS_ERR(pathname))
goto out;

1
include/linux/dcache.h
View File

@ -315,6 +315,7 @@ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
extern char *__d_path(const struct path *path, struct path *root, char *, int);
extern char *d_path(const struct path *, char *, int);
extern char *d_path_with_unreachable(const struct path *, char *, int);
extern char *__dentry_path(struct dentry *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);

5
include/linux/path.h
View File

@ -12,4 +12,9 @@ struct path {
extern void path_get(struct path *);
extern void path_put(struct path *);
static inline int path_equal(const struct path *path1, const struct path *path2)
{
return path1->mnt == path2->mnt && path1->dentry == path2->dentry;
}
#endif /* _LINUX_PATH_H */