process: Use ELF PHDR filesz instead of memsz where applicable (checked for consistency)

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/process.zig b/src/lib/process.zig
index 2a3ad73..641de7e 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -30,6 +30,7 @@ pub const ExeError = error{
     BadArch,
     BadBitLen,
     NotStaticExe,
+    SizeMismatch,
     BranchPerms,
 };
 
@@ -150,11 +151,12 @@ pub fn create(allocator: std.mem.Allocator, elf_buf: []align(@alignOf(elf.Elf64_
     var it = hdr.program_header_iterator(parse_source);
     while (try it.next()) |phdr| {
         if (phdr.p_type != elf.PT_LOAD) continue;
+        if (phdr.p_filesz == 0) continue;
         if (phdr.p_memsz == 0) continue;
+        if (phdr.p_filesz != phdr.p_memsz) return ExeError.SizeMismatch;
 
         // fixme: Could crash (out-of-bounds read).
-        // fixme: Use filesz instead of memsz for elf_buf and confirm that they're equal.
-        @memcpy(pages[phdr.p_offset .. phdr.p_offset + phdr.p_memsz], elf_buf[phdr.p_offset .. phdr.p_offset + phdr.p_memsz]);
+        @memcpy(pages[phdr.p_offset .. phdr.p_offset + phdr.p_memsz], elf_buf[phdr.p_offset .. phdr.p_offset + phdr.p_filesz]);
 
         const memsz_aligned = std.mem.alignForwardLog2(phdr.p_memsz, paging.log2_page_size);
         const num_mappings = @divExact(memsz_aligned, paging.page_size);