process: Fix ELF physical allocation overrun

Fixes #71.

1 files changed, 25 insertions, 14 deletions

diff --git a/src/lib/process.zig b/src/lib/process.zig
index c8e6d5e..265d9b3 100644
--- a/src/lib/process.zig
+++ b/src/lib/process.zig
@@ -47,7 +47,7 @@ pub const Info = struct {
     id: u16,
     thread_id: usize,
     trap_frame: TrapFrame,
-    pages: []align(paging.page_size) u8,
+    sections: std.ArrayList([]align(paging.page_size) u8),
     stack: []align(paging.page_size) u8,
     pc: usize,
     page_table: *paging.Table,
@@ -116,7 +116,14 @@ pub const Info = struct {
         if (self.thread_id == 0) {
             self.page_table.unmap();
             paging.free(self.page_table);
-            paging.free(self.pages);
+            self.freeSections();
+        }
+    }
+
+    fn freeSections(self: *Info) void {
+        defer self.sections.deinit();
+        for (self.sections.items) |section| {
+            paging.free(section);
         }
     }
 
@@ -225,11 +232,6 @@ pub fn create(allocator: Allocator, elf_buf: []align(@alignOf(elf.Elf64_Ehdr)) c
 
     try validateElfHeader(hdr, hdr_buf);
 
-    const len_aligned = std.mem.alignForwardLog2(elf_buf.len, paging.log2_page_size);
-    const num_pages = len_aligned / paging.page_size + 1;
-    const pages = try paging.zeroedAlloc(num_pages);
-    errdefer paging.free(pages);
-
     const procmem: *paging.Table = @ptrCast(try paging.zeroedAlloc(1));
     errdefer paging.free(procmem);
 
@@ -237,22 +239,31 @@ pub fn create(allocator: Allocator, elf_buf: []align(@alignOf(elf.Elf64_Ehdr)) c
 
     const parse_source = std.io.fixedBufferStream(elf_buf);
 
+    var sections = std.ArrayList([]align(paging.page_size) u8).init(allocator);
+
     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 or phdr.p_memsz == 0) continue;
-        if (phdr.p_filesz > elf_buf.len or phdr.p_memsz > pages.len) {
+        if (phdr.p_offset + phdr.p_filesz >= elf_buf.len) {
             return ExeError.LengthOutOfBounds;
         }
 
+        const offset = paging.offsetOf(phdr.p_vaddr);
+        const memsz_aligned = std.mem.alignForward(usize, offset + phdr.p_memsz, paging.page_size);
+        const num_pages = @divExact(memsz_aligned, paging.page_size);
+
+        const pages = try paging.zeroedAlloc(num_pages);
+        errdefer paging.free(pages);
+
+        try sections.append(pages);
+
         const sz = @min(phdr.p_filesz, phdr.p_memsz);
-        @memcpy(pages[phdr.p_offset .. phdr.p_offset + sz], elf_buf[phdr.p_offset .. phdr.p_offset + sz]);
+        @memcpy(pages[offset .. offset + sz], elf_buf[phdr.p_offset .. phdr.p_offset + sz]);
 
-        const memsz_aligned = std.mem.alignForwardLog2(phdr.p_memsz, paging.log2_page_size);
-        const num_mappings = @divExact(memsz_aligned, paging.page_size);
-        for (0..num_mappings) |page| {
+        for (0..num_pages) |page| {
             const vaddr = phdr.p_vaddr + page * paging.page_size;
-            const paddr = @intFromPtr(pages.ptr) + phdr.p_offset + page * paging.page_size;
+            const paddr = @intFromPtr(pages.ptr) + page * paging.page_size;
             const flags = paging.EntryFlags{
                 .valid = 1,
                 .read = @bitCast(phdr.p_flags & elf.PF_R != 0),
@@ -286,7 +297,7 @@ pub fn create(allocator: Allocator, elf_buf: []align(@alignOf(elf.Elf64_Ehdr)) c
         .id = next_pid,
         .thread_id = 0,
         .trap_frame = std.mem.zeroInit(TrapFrame, .{}),
-        .pages = pages,
+        .sections = sections,
         .stack = @ptrCast(stack),
         .pc = hdr.entry,
         .page_table = procmem,