avoid integer underflow when calling memset with 0

nix-community · Jun 14, 2023 · ca4a665 · ca4a665
1 parent a7a0a67
commit ca4a665
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/src/nix-ld.c b/src/nix-ld.c
@@ -202,7 +202,9 @@ static int elf_map(struct ld_ctx *ctx, int fd, const Phdr *prog_headers,
       size_t brk = ctx->load_addr + ph->p_vaddr + ph->p_filesz;
       size_t pgbrk = page_align(ctx, brk);
       size_t this_max = page_align(ctx, ph->p_vaddr + ph->p_memsz);
-      memset((void *)brk, 0, page_offset(ctx, pgbrk - brk));
+      if (page_offset(ctx, pgbrk - brk)) {
+        memset((void *)brk, 0, page_offset(ctx, pgbrk - brk));
+      }
 
       if (pgbrk - ctx->load_addr < this_max) {
         void *res = mmap((void *)pgbrk, ctx->load_addr + this_max - pgbrk, prot,