On Wed, Nov 1, 2023 at 12:57 PM Christian Göttsche
<cgzones@xxxxxxxxxxxxxx> wrote:
>
> Introduce reallocarray(3), a realloc(3) wrapper incorporating a
> multiplication overflow check.
>
> Add private implementation in case the function is not provided by the
> standard C library.
>
> Use in appropriate locations.
>
> Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Acked-by: James Carter <jwcart2@xxxxxxxxx>
> ---
> v3:
> - use SIZE_MAX and NULL instead of -1 and 0
> - fix indentation
> - drop RFC and split from original patch set
> ---
> libselinux/src/Makefile | 6 ++++++
> libselinux/src/get_context_list.c | 2 +-
> libselinux/src/matchpathcon.c | 4 ++--
> libselinux/src/selinux_internal.c | 16 ++++++++++++++++
> libselinux/src/selinux_internal.h | 4 ++++
> libselinux/src/selinux_restorecon.c | 3 +--
> 6 files changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/libselinux/src/Makefile b/libselinux/src/Makefile
> index cf830046..7aadb822 100644
> --- a/libselinux/src/Makefile
> +++ b/libselinux/src/Makefile
> @@ -108,6 +108,12 @@ ifeq (yes,$(shell printf '${H}include <string.h>\nint main(void){char*d,*s;strlc
> override CFLAGS += -DHAVE_STRLCPY
> endif
>
> +# check for reallocarray(3) availability
> +H := \#
> +ifeq (yes,$(shell printf '${H}include <stdlib.h>\nint main(void){reallocarray(NULL, 0, 0);return 0;}' | $(CC) -x c -o /dev/null - >/dev/null 2>&1 && echo yes))
> +override CFLAGS += -DHAVE_REALLOCARRAY
> +endif
> +
> SWIG_CFLAGS += -Wno-error -Wno-unused-variable -Wno-unused-but-set-variable -Wno-unused-parameter \
> -Wno-shadow -Wno-uninitialized -Wno-missing-prototypes -Wno-missing-declarations \
> -Wno-deprecated-declarations
> diff --git a/libselinux/src/get_context_list.c b/libselinux/src/get_context_list.c
> index 0342823c..9dafa519 100644
> --- a/libselinux/src/get_context_list.c
> +++ b/libselinux/src/get_context_list.c
> @@ -272,7 +272,7 @@ static int get_context_user(FILE * fp,
> continue;
> }
> if (security_check_context(usercon_str2) == 0) {
> - new_reachable = realloc(*reachable, (*nreachable + 2) * sizeof(char *));
> + new_reachable = reallocarray(*reachable, *nreachable + 2, sizeof(char *));
> if (!new_reachable) {
> context_free(usercon);
> rc = -1;
> diff --git a/libselinux/src/matchpathcon.c b/libselinux/src/matchpathcon.c
> index b98849d9..e44734c3 100644
> --- a/libselinux/src/matchpathcon.c
> +++ b/libselinux/src/matchpathcon.c
> @@ -96,8 +96,8 @@ static int add_array_elt(char *con)
> if (con_array_size) {
> while (con_array_used >= con_array_size) {
> con_array_size *= 2;
> - tmp = (char **)realloc(con_array, sizeof(char*) *
> - con_array_size);
> + tmp = (char **)reallocarray(con_array, con_array_size,
> + sizeof(char*));
> if (!tmp) {
> free_array_elts();
> return -1;
> diff --git a/libselinux/src/selinux_internal.c b/libselinux/src/selinux_internal.c
> index c2be7c0a..678bd99c 100644
> --- a/libselinux/src/selinux_internal.c
> +++ b/libselinux/src/selinux_internal.c
> @@ -1,5 +1,7 @@
> #include "selinux_internal.h"
>
> +#include <errno.h>
> +#include <stdlib.h>
> #include <string.h>
>
>
> @@ -16,3 +18,17 @@ size_t strlcpy(char *dest, const char *src, size_t size)
> return ret;
> }
> #endif /* HAVE_STRLCPY */
> +
> +#ifndef HAVE_REALLOCARRAY
> +void *reallocarray(void *ptr, size_t nmemb, size_t size)
> +{
> +
> + if (size && nmemb > SIZE_MAX / size) {
> + errno = ENOMEM;
> + return NULL;
> + }
> +
> + return realloc(ptr, nmemb * size);
> +
> +}
> +#endif /* HAVE_REALLOCARRAY */
> diff --git a/libselinux/src/selinux_internal.h b/libselinux/src/selinux_internal.h
> index 06f2c038..af69ff04 100644
> --- a/libselinux/src/selinux_internal.h
> +++ b/libselinux/src/selinux_internal.h
> @@ -98,4 +98,8 @@ extern int has_selinux_config ;
> size_t strlcpy(char *dest, const char *src, size_t size);
> #endif
>
> +#ifndef HAVE_REALLOCARRAY
> +void *reallocarray(void *ptr, size_t nmemb, size_t size);
> +#endif
> +
> #endif /* SELINUX_INTERNAL_H_ */
> diff --git a/libselinux/src/selinux_restorecon.c b/libselinux/src/selinux_restorecon.c
> index 7ef2d45d..38f10f1c 100644
> --- a/libselinux/src/selinux_restorecon.c
> +++ b/libselinux/src/selinux_restorecon.c
> @@ -175,8 +175,7 @@ static int add_exclude(const char *directory, bool who)
> return -1;
> }
>
> - tmp_list = realloc(exclude_lst,
> - sizeof(struct edir) * (exclude_count + 1));
> + tmp_list = reallocarray(exclude_lst, exclude_count + 1, sizeof(struct edir));
> if (!tmp_list)
> goto oom;
>
> --
> 2.42.0
>
