Re: [PATCH 2/8] cifs: Remove intermediate object of failed create reparse call

["Pali Rohár" <pali@kernel.org>]

Hello Steve, I was reading again implementation of smb2_compound_op()
function and if I understood it correctly, then out_iov and out_buftype
array parameters needs to have num_cmds+2 members. This is quite
unexpected, and this patch cause buffer overflow and memory leaks.
+2 is for CREATE and CLOSE operations added automatically by compound.

Surprisingly, no memory issue and neither corrupted packed I observed.
And therefore I thought that change is working fine.

I will send a new version of this change to increase array members and
free all members of array.

On Saturday 28 September 2024 23:59:42 Pali Rohár wrote:
> If CREATE was successful but SMB2_OP_SET_REPARSE failed then remove the
> intermediate object created by CREATE. Otherwise empty object stay on the
> server when reparse call failed.
> 
> This ensures that if the creating of special files is unsupported by the
> server then no empty file stay on the server as a result of unsupported
> operation.
> 
> Fixes: 102466f303ff ("smb: client: allow creating special files via reparse points")
> Signed-off-by: Pali Rohár <pali@kernel.org>
> ---
>  fs/smb/client/smb2inode.c | 21 +++++++++++++++++++--
>  1 file changed, 19 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/smb/client/smb2inode.c b/fs/smb/client/smb2inode.c
> index 11a1c53c64e0..af42f44bdcf4 100644
> --- a/fs/smb/client/smb2inode.c
> +++ b/fs/smb/client/smb2inode.c
> @@ -1205,6 +1205,8 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
>  	struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
>  	struct cifsFileInfo *cfile;
>  	struct inode *new = NULL;
> +	int out_buftype[2] = {};
> +	struct kvec out_iov[2];
>  	struct kvec in_iov[2];
>  	int cmds[2];
>  	int rc;
> @@ -1228,7 +1230,7 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
>  		cmds[1] = SMB2_OP_POSIX_QUERY_INFO;
>  		cifs_get_writable_path(tcon, full_path, FIND_WR_ANY, &cfile);
>  		rc = smb2_compound_op(xid, tcon, cifs_sb, full_path, &oparms,
> -				      in_iov, cmds, 2, cfile, NULL, NULL, NULL);
> +				      in_iov, cmds, 2, cfile, out_iov, out_buftype, NULL);
>  		if (!rc) {
>  			rc = smb311_posix_get_inode_info(&new, full_path,
>  							 data, sb, xid);
> @@ -1237,12 +1239,27 @@ struct inode *smb2_get_reparse_inode(struct cifs_open_info_data *data,
>  		cmds[1] = SMB2_OP_QUERY_INFO;
>  		cifs_get_writable_path(tcon, full_path, FIND_WR_ANY, &cfile);
>  		rc = smb2_compound_op(xid, tcon, cifs_sb, full_path, &oparms,
> -				      in_iov, cmds, 2, cfile, NULL, NULL, NULL);
> +				      in_iov, cmds, 2, cfile, out_iov, out_buftype, NULL);
>  		if (!rc) {
>  			rc = cifs_get_inode_info(&new, full_path,
>  						 data, sb, xid, NULL);
>  		}
>  	}
> +
> +	if (rc) {
> +		/*
> +		 * If CREATE was successful but SMB2_OP_SET_REPARSE failed then
> +		 * remove the intermediate object created by CREATE. Otherwise
> +		 * empty object stay on the server when reparse call failed.
> +		 */
> +		if (((struct smb2_hdr *)out_iov[0].iov_base)->Status == STATUS_SUCCESS &&
> +		    ((struct smb2_hdr *)out_iov[1].iov_base)->Status != STATUS_SUCCESS)
> +			smb2_unlink(xid, tcon, full_path, cifs_sb, NULL);
> +	}
> +
> +	free_rsp_buf(out_buftype[0], out_iov[0].iov_base);
> +	free_rsp_buf(out_buftype[1], out_iov[1].iov_base);
> +
>  	return rc ? ERR_PTR(rc) : new;
>  }
>  
> -- 
> 2.20.1
>