tools: bpf: make use of reallocarray

reallocarray() is a safer variant of realloc which checks for
multiplication overflow in case of array allocation.  Since it's
not available in Glibc < 2.26 import kernel's overflow.h and
add a static inline implementation when needed.  Use feature
detection to probe for existence of reallocarray.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

2 files changed, 11 insertions, 5 deletions

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 5390e7725e43..7a8e4c98ef1a 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -66,7 +66,7 @@ ifndef VERBOSE
 endif
 
 FEATURE_USER = .libbpf
-FEATURE_TESTS = libelf libelf-getphdrnum libelf-mmap bpf
+FEATURE_TESTS = libelf libelf-getphdrnum libelf-mmap bpf reallocarray
 FEATURE_DISPLAY = libelf bpf
 
 INCLUDES = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(ARCH)/include/uapi -I$(srctree)/tools/include/uapi -I$(srctree)/tools/perf
@@ -120,6 +120,10 @@ ifeq ($(feature-libelf-getphdrnum), 1)
   override CFLAGS += -DHAVE_ELF_GETPHDRNUM_SUPPORT
 endif
 
+ifeq ($(feature-reallocarray), 0)
+  override CFLAGS += -DCOMPAT_NEED_REALLOCARRAY
+endif
+
 # Append required CFLAGS
 override CFLAGS += $(EXTRA_WARNINGS)
 override CFLAGS += -Werror -Wall
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index f732237610e5..fd2c4433863d 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -22,6 +22,7 @@
  * License along with this program; if not,  see <http://www.gnu.org/licenses>
  */
 
+#define _GNU_SOURCE
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
@@ -41,6 +42,7 @@
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <sys/vfs.h>
+#include <tools/libc_compat.h>
 #include <libelf.h>
 #include <gelf.h>
 
@@ -321,7 +323,7 @@ bpf_object__add_program(struct bpf_object *obj, void *data, size_t size,
         progs = obj->programs;
         nr_progs = obj->nr_programs;
 
-        progs = realloc(progs, sizeof(progs[0]) * (nr_progs + 1));
+        progs = reallocarray(progs, nr_progs + 1, sizeof(progs[0]));
         if (!progs) {
                 /*
                  * In this case the original obj->programs
@@ -822,8 +824,8 @@ static int bpf_object__elf_collect(struct bpf_object *obj)
                                 continue;
                         }
 
-                        reloc = realloc(reloc,
-                                        sizeof(*obj->efile.reloc) * nr_reloc);
+                        reloc = reallocarray(reloc, nr_reloc,
+                                             sizeof(*obj->efile.reloc));
                         if (!reloc) {
                                 pr_warning("realloc failed\n");
                                 err = -ENOMEM;
@@ -1115,7 +1117,7 @@ bpf_program__reloc_text(struct bpf_program *prog, struct bpf_object *obj,
                         return -LIBBPF_ERRNO__RELOC;
                 }
                 new_cnt = prog->insns_cnt + text->insns_cnt;
-                new_insn = realloc(prog->insns, new_cnt * sizeof(*insn));
+                new_insn = reallocarray(prog->insns, new_cnt, sizeof(*insn));
                 if (!new_insn) {
                         pr_warning("oom in prog realloc\n");
                         return -ENOMEM;