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namei: allow nd_jump_link() to produce errors 

In preparation for LOOKUP_NO_MAGICLINKS, it's necessary to add the
ability for nd_jump_link() to return an error which the corresponding
get_link() caller must propogate back up to the VFS.

Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Aleksa Sarai <cyphar@cyphar.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Aleksa Sarai 2019-12-07 01:13:28 +11:00 committed by Al Viro
parent ce623f8987
commit 1bc82070fa
5 changed files with 17 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
fs/namei.c
View File

@ -859,7 +859,7 @@ static int nd_jump_root(struct nameidata *nd)
* Helper to directly jump to a known parsed path from ->get_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;
path_put(&nd->path);
@ -867,6 +867,7 @@ void nd_jump_link(struct path *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)

3
fs/proc/base.c
View File

@ -1626,8 +1626,7 @@ static const char *proc_pid_get_link(struct dentry *dentry,
if (error)
goto out;
nd_jump_link(&path);
return NULL;
error = nd_jump_link(&path);
out:
return ERR_PTR(error);
}

14
fs/proc/namespaces.c
View File

@ -51,11 +51,15 @@ static const char *proc_ns_get_link(struct dentry *dentry,
if (!task)
return ERR_PTR(-EACCES);
if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
error = ns_get_path(&ns_path, task, ns_ops);
if (!error)
nd_jump_link(&ns_path);
}
if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto out;
error = ns_get_path(&ns_path, task, ns_ops);
if (error)
goto out;
error = nd_jump_link(&ns_path);
out:
put_task_struct(task);
return ERR_PTR(error);
}

2
include/linux/namei.h
View File

@ -69,7 +69,7 @@ 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 __must_check nd_jump_link(struct path *path);
static inline void nd_terminate_link(void *name, size_t len, size_t maxlen)
{

6
security/apparmor/apparmorfs.c
View File

@ -2573,16 +2573,18 @@ static const char *policy_get_link(struct dentry *dentry,
{
struct aa_ns *ns;
struct path path;
int error;
if (!dentry)
return ERR_PTR(-ECHILD);
ns = aa_get_current_ns();
path.mnt = mntget(aafs_mnt);
path.dentry = dget(ns_dir(ns));
nd_jump_link(&path);
error = nd_jump_link(&path);
aa_put_ns(ns);
return NULL;
return ERR_PTR(error);
}
static int policy_readlink(struct dentry *dentry, char __user *buffer,