Re: [PATCH 2/2] afs: Fix afs_xattr_get_yfs() to not try freeing an error value

[walter harms]

Am 12.05.2019 09:45, schrieb David Howells:
> afs_xattr_get_yfs() tries to free yacl, which may hold an error value (say
> if yfs_fs_fetch_opaque_acl() failed and returned an error).
> 
> Fix this by allocating yacl up front (since it's a fixed-length struct,
> unlike afs_acl) and passing it in to the RPC function.  This also allows
> the flags to be placed in the object rather than passing them through to
> the RPC function.
> 
> Fixes: ae46578b963f ("afs: Get YFS ACLs and information through xattrs")
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
> 
>  fs/afs/internal.h  |    2 +
>  fs/afs/xattr.c     |   86 ++++++++++++++++++++++++++++------------------------
>  fs/afs/yfsclient.c |   29 ++++--------------
>  3 files changed, 53 insertions(+), 64 deletions(-)
> 
> diff --git a/fs/afs/internal.h b/fs/afs/internal.h
> index b3cd6e8ad59d..74ee0f8ef8dd 100644
> --- a/fs/afs/internal.h
> +++ b/fs/afs/internal.h
> @@ -1382,7 +1382,7 @@ struct yfs_acl {
>  };
>  
>  extern void yfs_free_opaque_acl(struct yfs_acl *);
> -extern struct yfs_acl *yfs_fs_fetch_opaque_acl(struct afs_fs_cursor *, unsigned int);
> +extern struct yfs_acl *yfs_fs_fetch_opaque_acl(struct afs_fs_cursor *, struct yfs_acl *);
>  extern int yfs_fs_store_opaque_acl2(struct afs_fs_cursor *, const struct afs_acl *);
>  
>  /*
> diff --git a/fs/afs/xattr.c b/fs/afs/xattr.c
> index b6c44e75b361..d12bcda911e1 100644
> --- a/fs/afs/xattr.c
> +++ b/fs/afs/xattr.c
> @@ -148,9 +148,8 @@ static int afs_xattr_get_yfs(const struct xattr_handler *handler,
>  	struct afs_vnode *vnode = AFS_FS_I(inode);
>  	struct yfs_acl *yacl = NULL;
>  	struct key *key;
> -	unsigned int flags = 0;
>  	char buf[16], *data;
> -	int which = 0, dsize, ret;
> +	int which = 0, dsize, ret = -ENOMEM;
>  
>  	if (strcmp(name, "acl") == 0)
>  		which = 0;
> @@ -163,20 +162,26 @@ static int afs_xattr_get_yfs(const struct xattr_handler *handler,
>  	else
>  		return -EOPNOTSUPP;
>  
> +	yacl = kzalloc(sizeof(struct yfs_acl), GFP_KERNEL);
> +	if (!yacl)
> +		goto error;
> +
>  	if (which == 0)
> -		flags |= YFS_ACL_WANT_ACL;
> +		yacl->flags |= YFS_ACL_WANT_ACL;
>  	else if (which == 3)
> -		flags |= YFS_ACL_WANT_VOL_ACL;
> +		yacl->flags |= YFS_ACL_WANT_VOL_ACL;
>  
>  	key = afs_request_key(vnode->volume->cell);
> -	if (IS_ERR(key))
> -		return PTR_ERR(key);
> +	if (IS_ERR(key)) {
> +		ret = PTR_ERR(key);
> +		goto error_yacl;
> +	}
>  
>  	ret = -ERESTARTSYS;
>  	if (afs_begin_vnode_operation(&fc, vnode, key)) {
>  		while (afs_select_fileserver(&fc)) {
>  			fc.cb_break = afs_calc_vnode_cb_break(vnode);
> -			yacl = yfs_fs_fetch_opaque_acl(&fc, flags);
> +			yfs_fs_fetch_opaque_acl(&fc, yacl);
>  		}
>  
>  		afs_check_for_remote_deletion(&fc, fc.vnode);
> @@ -184,44 +189,45 @@ static int afs_xattr_get_yfs(const struct xattr_handler *handler,
>  		ret = afs_end_vnode_operation(&fc);
>  	}
>  
> -	if (ret == 0) {
> -		switch (which) {
> -		case 0:
> -			data = yacl->acl->data;
> -			dsize = yacl->acl->size;
> -			break;
> -		case 1:
> -			data = buf;
> -			dsize = snprintf(buf, sizeof(buf), "%u",
> -					 yacl->inherit_flag);
> -			break;
> -		case 2:
> -			data = buf;
> -			dsize = snprintf(buf, sizeof(buf), "%u",
> -					 yacl->num_cleaned);
> -			break;
> -		case 3:
> -			data = yacl->vol_acl->data;
> -			dsize = yacl->vol_acl->size;
> -			break;
> -		default:
> -			ret = -EOPNOTSUPP;
> -			goto out;
> -		}
> +	if (ret < 0)
> +		goto error_key;
> +
> +	switch (which) {
> +	case 0:
> +		data = yacl->acl->data;
> +		dsize = yacl->acl->size;
> +		break;
> +	case 1:
> +		data = buf;
> +		dsize = snprintf(buf, sizeof(buf), "%u", yacl->inherit_flag);
> +		break;
> +	case 2:
> +		data = buf;
> +		dsize = snprintf(buf, sizeof(buf), "%u", yacl->num_cleaned);
> +		break;
> +	case 3:
> +		data = yacl->vol_acl->data;
> +		dsize = yacl->vol_acl->size;
> +		break;
> +	default:
> +		ret = -EOPNOTSUPP;
> +		goto error_key;
> +	}
>  
> -		ret = dsize;
> -		if (size > 0) {
> -			if (dsize > size) {
> -				ret = -ERANGE;
> -				goto out;
> -			}
> -			memcpy(buffer, data, dsize);
> +	ret = dsize;
> +	if (size > 0) {
> +		if (dsize > size) {
> +			ret = -ERANGE;
> +			goto error_key;
>  		}
> +		memcpy(buffer, data, dsize);
>  	}
>  

i am confused: if size is <= 0 then the error is in dsize ?

re,
 wh

> -out:
> -	yfs_free_opaque_acl(yacl);
> +error_key:
>  	key_put(key);
> +error_yacl:
> +	yfs_free_opaque_acl(yacl);
> +error:
>  	return ret;
>  }
>  
> diff --git a/fs/afs/yfsclient.c b/fs/afs/yfsclient.c
> index 6cf7d161baa1..d3e9e3fe0b58 100644
> --- a/fs/afs/yfsclient.c
> +++ b/fs/afs/yfsclient.c
> @@ -2333,12 +2333,6 @@ void yfs_free_opaque_acl(struct yfs_acl *yacl)
>  	}
>  }
>  
> -static void yfs_destroy_fs_fetch_opaque_acl(struct afs_call *call)
> -{
> -	yfs_free_opaque_acl(call->reply[0]);
> -	afs_flat_call_destructor(call);
> -}
> -
>  /*
>   * YFS.FetchOpaqueACL operation type
>   */
> @@ -2346,18 +2340,17 @@ static const struct afs_call_type yfs_RXYFSFetchOpaqueACL = {
>  	.name		= "YFS.FetchOpaqueACL",
>  	.op		= yfs_FS_FetchOpaqueACL,
>  	.deliver	= yfs_deliver_fs_fetch_opaque_acl,
> -	.destructor	= yfs_destroy_fs_fetch_opaque_acl,
> +	.destructor	= afs_flat_call_destructor,
>  };
>  
>  /*
>   * Fetch the YFS advanced ACLs for a file.
>   */
>  struct yfs_acl *yfs_fs_fetch_opaque_acl(struct afs_fs_cursor *fc,
> -					unsigned int flags)
> +					struct yfs_acl *yacl)
>  {
>  	struct afs_vnode *vnode = fc->vnode;
>  	struct afs_call *call;
> -	struct yfs_acl *yacl;
>  	struct afs_net *net = afs_v2net(vnode);
>  	__be32 *bp;
>  
> @@ -2370,19 +2363,15 @@ struct yfs_acl *yfs_fs_fetch_opaque_acl(struct afs_fs_cursor *fc,
>  				   sizeof(__be32) * 2 +
>  				   sizeof(struct yfs_xdr_YFSFetchStatus) +
>  				   sizeof(struct yfs_xdr_YFSVolSync));
> -	if (!call)
> -		goto nomem;
> -
> -	yacl = kzalloc(sizeof(struct yfs_acl), GFP_KERNEL);
> -	if (!yacl)
> -		goto nomem_call;
> +	if (!call) {
> +		fc->ac.error = -ENOMEM;
> +		return ERR_PTR(-ENOMEM);
> +	}
>  
> -	yacl->flags = flags;
>  	call->key = fc->key;
>  	call->reply[0] = yacl;
>  	call->reply[1] = vnode;
>  	call->reply[2] = NULL; /* volsync */
> -	call->ret_reply0 = true;
>  
>  	/* marshall the parameters */
>  	bp = call->request;
> @@ -2396,12 +2385,6 @@ struct yfs_acl *yfs_fs_fetch_opaque_acl(struct afs_fs_cursor *fc,
>  	trace_afs_make_fs_call(call, &vnode->fid);
>  	afs_make_call(&fc->ac, call, GFP_KERNEL);
>  	return (struct yfs_acl *)afs_wait_for_call_to_complete(call, &fc->ac);
> -
> -nomem_call:
> -	afs_put_call(call);
> -nomem:
> -	fc->ac.error = -ENOMEM;
> -	return ERR_PTR(-ENOMEM);
>  }
>  
>  /*
> 
>