process: Fix create() panicking on ELFs smaller than the ELF buffer size

Fixes #65.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/lib/process.zig b/src/lib/process.zig
index 8aaf972..c167363 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -33,6 +33,7 @@ pub const Error = error{
 };
 
 pub const ExeError = error{
+    TooSmall,
     BadEndian,
     BadArch,
     BadBitLen,
@@ -226,8 +227,12 @@ pub fn switchTo(proc: *Info) noreturn {
     unreachable;
 }
 
+const HdrBuf = *align(@alignOf(elf.Elf64_Ehdr)) const [@sizeOf(elf.Elf64_Ehdr)]u8;
+
 pub fn create(allocator: std.mem.Allocator, elf_buf: []align(@alignOf(elf.Elf64_Ehdr)) const u8) !*Info {
-    const hdr_buf: *align(@alignOf(elf.Elf64_Ehdr)) const [@sizeOf(elf.Elf64_Ehdr)]u8 = elf_buf[0..@sizeOf(elf.Elf64_Ehdr)];
+    if (elf_buf.len < @sizeOf(elf.Elf64_Ehdr)) return ExeError.TooSmall;
+
+    const hdr_buf: HdrBuf = elf_buf[0..@sizeOf(elf.Elf64_Ehdr)];
     const hdr = try elf.Header.parse(@ptrCast(hdr_buf));
 
     try validateElfHeader(hdr, hdr_buf);