On Tue, Nov 05, 2019 at 08:05:47PM +1100, Aleksa Sarai wrote:
@@ -862,6 +870,8 @@ static int nd_jump_root(struct nameidata *nd) void nd_jump_link(struct path *path) { struct nameidata *nd = current->nameidata;
- nd->last_magiclink.same_mnt = (nd->path.mnt == path->mnt); path_put(&nd->path);
nd->path = *path; @@ -1082,6 +1092,10 @@ const char *get_link(struct nameidata *nd) if (nd->flags & LOOKUP_MAGICLINK_JUMPED) { if (unlikely(nd->flags & LOOKUP_NO_MAGICLINKS)) return ERR_PTR(-ELOOP);
if (unlikely(nd->flags & LOOKUP_NO_XDEV)) {if (!nd->last_magiclink.same_mnt)return ERR_PTR(-EXDEV);}
Ugh... Wouldn't it be better to take that logics (some equivalent thereof) into nd_jump_link()? Or just have nd_jump_link() return an error...
I mean, look at the callers of nd_jump_link(). static const char *policy_get_link(struct dentry *dentry, struct inode *inode, struct delayed_call *done) { struct aa_ns *ns; struct path path;
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); aa_put_ns(ns);
return NULL; } - very close to the end of ->get_link() instance.
static const char *proc_pid_get_link(struct dentry *dentry, struct inode *inode, struct delayed_call *done) { struct path path; int error = -EACCES;
if (!dentry) return ERR_PTR(-ECHILD);
/* Are we allowed to snoop on the tasks file descriptors? */ if (!proc_fd_access_allowed(inode)) goto out;
error = PROC_I(inode)->op.proc_get_link(dentry, &path); if (error) goto out;
nd_jump_link(&path); return NULL; out: return ERR_PTR(error); } Ditto.
static const char *proc_ns_get_link(struct dentry *dentry, struct inode *inode, struct delayed_call *done) { const struct proc_ns_operations *ns_ops = PROC_I(inode)->ns_ops; struct task_struct *task; struct path ns_path; void *error = ERR_PTR(-EACCES);
if (!dentry) return ERR_PTR(-ECHILD);
task = get_proc_task(inode); if (!task) return error;
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); } put_task_struct(task); return error; }
The same. And that's it - there's no more of them. So how about this in the beginning of the series, then having your magiclink error handling done in nd_jump_link()?
diff --git a/fs/namei.c b/fs/namei.c index 671c3c1a3425..8ec924813c30 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -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) +const char *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 NULL; }
static inline void put_link(struct nameidata *nd) diff --git a/fs/proc/base.c b/fs/proc/base.c index ebea9501afb8..ac4e57a3dfa5 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1626,8 +1626,7 @@ static const char *proc_pid_get_link(struct dentry *dentry, if (error) goto out;
- nd_jump_link(&path); - return NULL; + return nd_jump_link(&path); out: return ERR_PTR(error); } diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c index dd2b35f78b09..dde0c501b2f3 100644 --- a/fs/proc/namespaces.c +++ b/fs/proc/namespaces.c @@ -54,7 +54,7 @@ static const char *proc_ns_get_link(struct dentry *dentry, 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); + error = nd_jump_link(&ns_path); } put_task_struct(task); return error; diff --git a/include/linux/namei.h b/include/linux/namei.h index 397a08ade6a2..f3e8438e5631 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -68,7 +68,7 @@ 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 const char *nd_jump_link(struct path *path);
static inline void nd_terminate_link(void *name, size_t len, size_t maxlen) { diff --git a/security/apparmor/apparmorfs.c b/security/apparmor/apparmorfs.c index 45d13b6462aa..98aef94b4777 100644 --- a/security/apparmor/apparmorfs.c +++ b/security/apparmor/apparmorfs.c @@ -2453,18 +2453,16 @@ static const char *policy_get_link(struct dentry *dentry, struct inode *inode, struct delayed_call *done) { - struct aa_ns *ns; - struct path path; - - 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); - aa_put_ns(ns); - - return NULL; + const char *err = ERR_PTR(-ECHILD); + + if (dentry) { + struct aa_ns *ns = aa_get_current_ns(); + struct path path = {.mnt = mntget(aafs_mnt), + .dentry = ns_dir(ns)}; + err = nd_jump_link(&path); + aa_put_ns(ns); + } + return err; }
static int policy_readlink(struct dentry *dentry, char __user *buffer,