On Mon, Aug 14, 2023 at 9:41 AM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Use fseek(3) instead of rewind(3) to detect failures.
>
> Drop the final rewind in digest_add_specfile(), since all callers are
> going to close the stream without any further action.
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Acked-by: James Carter <jwcart2@xxxxxxxxx>
> ---
> libselinux/src/is_customizable_type.c | 7 ++++++-
> libselinux/src/label_backends_android.c | 5 ++++-
> libselinux/src/label_file.c | 16 +++++++++++++---
> libselinux/src/label_media.c | 5 ++++-
> libselinux/src/label_support.c | 5 +++--
> libselinux/src/label_x.c | 5 ++++-
> 6 files changed, 34 insertions(+), 9 deletions(-)
>
> diff --git a/libselinux/src/is_customizable_type.c b/libselinux/src/is_customizable_type.c
> index f83e1e83..9be50174 100644
> --- a/libselinux/src/is_customizable_type.c
> +++ b/libselinux/src/is_customizable_type.c
> @@ -31,7 +31,12 @@ static void customizable_init(void)
> while (fgets_unlocked(buf, selinux_page_size, fp) && ctr < UINT_MAX) {
> ctr++;
> }
> - rewind(fp);
> +
> + if (fseek(fp, 0L, SEEK_SET) == -1) {
> + fclose(fp);
> + return;
> + }
> +
> if (ctr) {
> list =
> (char **) calloc(sizeof(char *),
> diff --git a/libselinux/src/label_backends_android.c b/libselinux/src/label_backends_android.c
> index c2d78360..6494f3cd 100644
> --- a/libselinux/src/label_backends_android.c
> +++ b/libselinux/src/label_backends_android.c
> @@ -208,7 +208,10 @@ static int init(struct selabel_handle *rec, const struct selinux_opt *opts,
> goto finish;
>
> maxnspec = data->nspec;
> - rewind(fp);
> +
> + status = fseek(fp, 0L, SEEK_SET);
> + if (status == -1)
> + goto finish;
> }
> }
>
> diff --git a/libselinux/src/label_file.c b/libselinux/src/label_file.c
> index 471fd56b..a5677411 100644
> --- a/libselinux/src/label_file.c
> +++ b/libselinux/src/label_file.c
> @@ -519,12 +519,16 @@ static char *rolling_append(char *current, const char *suffix, size_t max)
> return current;
> }
>
> -static bool fcontext_is_binary(FILE *fp)
> +static int fcontext_is_binary(FILE *fp)
> {
> uint32_t magic;
> + int rc;
>
> size_t len = fread(&magic, sizeof(magic), 1, fp);
> - rewind(fp);
> +
> + rc = fseek(fp, 0L, SEEK_SET);
> + if (rc == -1)
> + return -1;
>
> return (len && (magic == SELINUX_MAGIC_COMPILED_FCONTEXT));
> }
> @@ -622,7 +626,13 @@ static int process_file(const char *path, const char *suffix,
> if (fp == NULL)
> return -1;
>
> - rc = fcontext_is_binary(fp) ?
> + rc = fcontext_is_binary(fp);
> + if (rc < 0) {
> + (void) fclose(fp);
> + return -1;
> + }
> +
> + rc = rc ?
> load_mmap(fp, sb.st_size, rec, found_path) :
> process_text_file(fp, rec, found_path);
> if (!rc)
> diff --git a/libselinux/src/label_media.c b/libselinux/src/label_media.c
> index f09461ab..b3443b47 100644
> --- a/libselinux/src/label_media.c
> +++ b/libselinux/src/label_media.c
> @@ -130,7 +130,10 @@ static int init(struct selabel_handle *rec, const struct selinux_opt *opts,
> goto finish;
> memset(data->spec_arr, 0, sizeof(spec_t)*data->nspec);
> maxnspec = data->nspec;
> - rewind(fp);
> +
> + status = fseek(fp, 0L, SEEK_SET);
> + if (status == -1)
> + goto finish;
> }
> }
> free(line_buf);
> diff --git a/libselinux/src/label_support.c b/libselinux/src/label_support.c
> index 94fb6697..f7ab9292 100644
> --- a/libselinux/src/label_support.c
> +++ b/libselinux/src/label_support.c
> @@ -174,12 +174,13 @@ int digest_add_specfile(struct selabel_digest *digest, FILE *fp,
> digest->hashbuf = tmp_buf;
>
> if (fp) {
> - rewind(fp);
> + if (fseek(fp, 0L, SEEK_SET) == -1)
> + return -1;
> +
> if (fread(digest->hashbuf + (digest->hashbuf_size - buf_len),
> 1, buf_len, fp) != buf_len)
> return -1;
>
> - rewind(fp);
> } else if (from_addr) {
> tmp_buf = memcpy(digest->hashbuf +
> (digest->hashbuf_size - buf_len),
> diff --git a/libselinux/src/label_x.c b/libselinux/src/label_x.c
> index e80bf107..e15190ca 100644
> --- a/libselinux/src/label_x.c
> +++ b/libselinux/src/label_x.c
> @@ -157,7 +157,10 @@ static int init(struct selabel_handle *rec, const struct selinux_opt *opts,
> goto finish;
> memset(data->spec_arr, 0, sizeof(spec_t)*data->nspec);
> maxnspec = data->nspec;
> - rewind(fp);
> +
> + status = fseek(fp, 0L, SEEK_SET);
> + if (status == -1)
> + goto finish;
> }
> }
> free(line_buf);
> --
> 2.40.1
>
