afs: Get an AFS3 ACL as an xattr

Implement an xattr on AFS files called "afs.acl" that retrieves a file's
ACL.  It returns the raw AFS3 ACL from the result of calling FS.FetchACL,
leaving any interpretation to userspace.

Note that whilst YFS servers will respond to FS.FetchACL, this will render
a more-advanced YFS ACL down.  Use "afs.yfs.acl" instead for that.

Signed-off-by: David Howells <dhowells@redhat.com>

4 files changed, 183 insertions, 0 deletions

diff --git a/fs/afs/afs_fs.h b/fs/afs/afs_fs.h
index ddfa88a7a9c0..4df1f1eec0ab 100644
--- a/fs/afs/afs_fs.h
+++ b/fs/afs/afs_fs.h
@@ -17,6 +17,7 @@
 
 enum AFS_FS_Operations {
         FSFETCHDATA             = 130,  /* AFS Fetch file data */
+        FSFETCHACL              = 131,  /* AFS Fetch file ACL */
         FSFETCHSTATUS           = 132,  /* AFS Fetch file status */
         FSSTOREDATA             = 133,  /* AFS Store file data */
         FSSTORESTATUS           = 135,  /* AFS Store file status */
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 9b73a57aa5cb..283f486c59f4 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -2391,3 +2391,125 @@ int afs_fs_inline_bulk_status(struct afs_fs_cursor *fc,
         afs_make_call(&fc->ac, call, GFP_NOFS);
         return afs_wait_for_call_to_complete(call, &fc->ac);
 }
+
+/*
+ * deliver reply data to an FS.FetchACL
+ */
+static int afs_deliver_fs_fetch_acl(struct afs_call *call)
+{
+        struct afs_vnode *vnode = call->reply[1];
+        struct afs_acl *acl;
+        const __be32 *bp;
+        unsigned int size;
+        int ret;
+
+        _enter("{%u}", call->unmarshall);
+
+        switch (call->unmarshall) {
+        case 0:
+                afs_extract_to_tmp(call);
+                call->unmarshall++;
+
+                /* extract the returned data length */
+        case 1:
+                ret = afs_extract_data(call, true);
+                if (ret < 0)
+                        return ret;
+
+                size = call->count2 = ntohl(call->tmp);
+                size = round_up(size, 4);
+
+                acl = kmalloc(struct_size(acl, data, size), GFP_KERNEL);
+                if (!acl)
+                        return -ENOMEM;
+                call->reply[0] = acl;
+                acl->size = call->count2;
+                afs_extract_begin(call, acl->data, size);
+                call->unmarshall++;
+
+                /* extract the returned data */
+        case 2:
+                ret = afs_extract_data(call, true);
+                if (ret < 0)
+                        return ret;
+
+                afs_extract_to_buf(call, (21 + 6) * 4);
+                call->unmarshall++;
+
+                /* extract the metadata */
+        case 3:
+                ret = afs_extract_data(call, false);
+                if (ret < 0)
+                        return ret;
+
+                bp = call->buffer;
+                ret = afs_decode_status(call, &bp, &vnode->status, vnode,
+                                        &vnode->status.data_version, NULL);
+                if (ret < 0)
+                        return ret;
+                xdr_decode_AFSVolSync(&bp, call->reply[2]);
+
+                call->unmarshall++;
+
+        case 4:
+                break;
+        }
+
+        _leave(" = 0 [done]");
+        return 0;
+}
+
+static void afs_destroy_fs_fetch_acl(struct afs_call *call)
+{
+        kfree(call->reply[0]);
+        afs_flat_call_destructor(call);
+}
+
+/*
+ * FS.FetchACL operation type
+ */
+static const struct afs_call_type afs_RXFSFetchACL = {
+        .name           = "FS.FetchACL",
+        .op             = afs_FS_FetchACL,
+        .deliver        = afs_deliver_fs_fetch_acl,
+        .destructor     = afs_destroy_fs_fetch_acl,
+};
+
+/*
+ * Fetch the ACL for a file.
+ */
+struct afs_acl *afs_fs_fetch_acl(struct afs_fs_cursor *fc)
+{
+        struct afs_vnode *vnode = fc->vnode;
+        struct afs_call *call;
+        struct afs_net *net = afs_v2net(vnode);
+        __be32 *bp;
+
+        _enter(",%x,{%llx:%llu},,",
+               key_serial(fc->key), vnode->fid.vid, vnode->fid.vnode);
+
+        call = afs_alloc_flat_call(net, &afs_RXFSFetchACL, 16, (21 + 6) * 4);
+        if (!call) {
+                fc->ac.error = -ENOMEM;
+                return ERR_PTR(-ENOMEM);
+        }
+
+        call->key = fc->key;
+        call->reply[0] = NULL;
+        call->reply[1] = vnode;
+        call->reply[2] = NULL; /* volsync */
+        call->ret_reply0 = true;
+
+        /* marshall the parameters */
+        bp = call->request;
+        bp[0] = htonl(FSFETCHACL);
+        bp[1] = htonl(vnode->fid.vid);
+        bp[2] = htonl(vnode->fid.vnode);
+        bp[3] = htonl(vnode->fid.unique);
+
+        call->cb_break = fc->cb_break;
+        afs_use_fs_server(call, fc->cbi);
+        trace_afs_make_fs_call(call, &vnode->fid);
+        afs_make_call(&fc->ac, call, GFP_KERNEL);
+        return (struct afs_acl *)afs_wait_for_call_to_complete(call, &fc->ac);
+}
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index 585a5952f608..683b802c20ea 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -977,6 +977,13 @@ extern int afs_fs_fetch_status(struct afs_fs_cursor *, struct afs_net *,
                                struct afs_fid *, struct afs_file_status *,
                                struct afs_callback *, struct afs_volsync *);
 
+struct afs_acl {
+        u32     size;
+        u8      data[];
+};
+
+extern struct afs_acl *afs_fs_fetch_acl(struct afs_fs_cursor *);
+
 /*
  * fs_probe.c
  */
diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
index e729ee3d4b02..b7d3d714d8ff 100644
--- a/fs/afs/xattr.c
+++ b/fs/afs/xattr.c
@@ -16,6 +16,7 @@
 #include "internal.h"
 
 static const char afs_xattr_list[] =
+        "afs.acl\0"
         "afs.cell\0"
         "afs.fid\0"
         "afs.volume";
@@ -34,6 +35,57 @@ ssize_t afs_listxattr(struct dentry *dentry, char *buffer, size_t size)
 }
 
 /*
+ * Get a file's ACL.
+ */
+static int afs_xattr_get_acl(const struct xattr_handler *handler,
+                             struct dentry *dentry,
+                             struct inode *inode, const char *name,
+                             void *buffer, size_t size)
+{
+        struct afs_fs_cursor fc;
+        struct afs_vnode *vnode = AFS_FS_I(inode);
+        struct afs_acl *acl = NULL;
+        struct key *key;
+        int ret;
+
+        key = afs_request_key(vnode->volume->cell);
+        if (IS_ERR(key))
+                return PTR_ERR(key);
+
+        ret = -ERESTARTSYS;
+        if (afs_begin_vnode_operation(&fc, vnode, key)) {
+                while (afs_select_fileserver(&fc)) {
+                        fc.cb_break = afs_calc_vnode_cb_break(vnode);
+                        acl = afs_fs_fetch_acl(&fc);
+                }
+
+                afs_check_for_remote_deletion(&fc, fc.vnode);
+                afs_vnode_commit_status(&fc, vnode, fc.cb_break);
+                ret = afs_end_vnode_operation(&fc);
+        }
+
+        if (ret == 0) {
+                ret = acl->size;
+                if (size > 0) {
+                        ret = -ERANGE;
+                        if (acl->size > size)
+                                return -ERANGE;
+                        memcpy(buffer, acl->data, acl->size);
+                        ret = acl->size;
+                }
+                kfree(acl);
+        }
+
+        key_put(key);
+        return ret;
+}
+
+static const struct xattr_handler afs_xattr_afs_acl_handler = {
+        .name   = "afs.acl",
+        .get    = afs_xattr_get_acl,
+};
+
+/*
  * Get the name of the cell on which a file resides.
  */
 static int afs_xattr_get_cell(const struct xattr_handler *handler,
@@ -123,6 +175,7 @@ static const struct xattr_handler afs_xattr_afs_volume_handler = {
 };
 
 const struct xattr_handler *afs_xattr_handlers[] = {
+        &afs_xattr_afs_acl_handler,
         &afs_xattr_afs_cell_handler,
         &afs_xattr_afs_fid_handler,
         &afs_xattr_afs_volume_handler,