Re: [PATCH v2] btrfs-progs: receive: add support for fs-verity

[Eric Biggers <ebiggers@kernel.org>]

On Thu, Jul 28, 2022 at 11:14:35AM -0700, Boris Burkov wrote:
> +static int process_enable_verity(const char *path, u8 algorithm, u32 block_size,
> +				 int salt_len, char *salt,
> +				 int sig_len, char *sig, void *user)
> +{
> +	int ret;
> +	struct btrfs_receive *rctx = user;
> +	char full_path[PATH_MAX];
> +	struct fsverity_enable_arg verity_args = {
> +		.version = 1,
> +		.hash_algorithm = algorithm,
> +		.block_size = block_size,
> +	};
> +	if (salt_len) {
> +		verity_args.salt_size = salt_len;
> +		verity_args.salt_ptr = (__u64)salt;
> +	}
> +	if (sig_len) {
> +		verity_args.sig_size = sig_len;
> +		verity_args.sig_ptr = (__u64)sig;
> +	}

Casting a pointer to a __u64 needs to be done using (__u64)(uintptr_t),
otherwise it will cause a warning on 32-bit platforms.

> +	/*
> +	 * Enabling verity denies write access, so it cannot be done with an
> +	 * open writeable file descriptor.
> +	 */
> +	close_inode_for_write(rctx);
> +	ret = ioctl(ioctl_fd, FS_IOC_ENABLE_VERITY, &verity_args);
> +	if (ret < 0)
> +		fprintf(stderr, "Failed to enable verity on %s: %d\n", full_path, ret);

Errors from ioctl() are returned in errno, not in the return value.

- Eric