This allows for users of kernfs to create custom (and possibly less restrictive) permission checks for kernfs_nodes. The default is unchanged. This patch is part of the cgroupns unprivileged subtree management patchset.
Cc: [email protected] Signed-off-by: Aleksa Sarai <[email protected]> --- fs/kernfs/inode.c | 13 ++++++++++++- include/linux/kernfs.h | 3 +++ 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/fs/kernfs/inode.c b/fs/kernfs/inode.c index 63b925d5ba1e..e82b8e5aa643 100644 --- a/fs/kernfs/inode.c +++ b/fs/kernfs/inode.c @@ -364,15 +364,26 @@ void kernfs_evict_inode(struct inode *inode) int kernfs_iop_permission(struct inode *inode, int mask) { struct kernfs_node *kn; + struct kernfs_syscall_ops *scops; + int ret; if (mask & MAY_NOT_BLOCK) return -ECHILD; kn = inode->i_private; + if (!kernfs_get_active(kn)) + return -ENODEV; mutex_lock(&kernfs_mutex); kernfs_refresh_inode(kn, inode); mutex_unlock(&kernfs_mutex); - return generic_permission(inode, mask); + scops = kernfs_root(kn)->syscall_ops; + if (unlikely(scops && scops->permission)) + ret = scops->permission(inode, kn, mask); + else + ret = generic_permission(inode, mask); + + kernfs_put_active(kn); + return ret; } diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h index 96356ef012de..373b5a888a81 100644 --- a/include/linux/kernfs.h +++ b/include/linux/kernfs.h @@ -16,6 +16,7 @@ #include <linux/rbtree.h> #include <linux/atomic.h> #include <linux/wait.h> +#include <linux/fs.h> struct file; struct dentry; @@ -154,6 +155,8 @@ struct kernfs_syscall_ops { const char *new_name); int (*show_path)(struct seq_file *sf, struct kernfs_node *kn, struct kernfs_root *root); + int (*permission)(struct inode *inode, struct kernfs_node *kn, + int mask); }; struct kernfs_root { -- 2.9.0
