Add seccomp sandbox for non-SFI NaCl

components/nacl/loader/nonsfi/elf_loader.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/nacl/loader/nonsfi/elf_loader.h"
 
 #include <elf.h>
 #include <link.h>
 
 #include <cstring>
@@ skipping 252 matching lines @@
   }
   return data_->ehdr.e_entry + data_->load_bias;
 }
 
 NaClErrorCode ElfImage::Read(struct NaClDesc* descriptor) {
   DCHECK(!data_);
 
   ::scoped_ptr<Data> data(new Data);
 
   // Read elf header.
-  ssize_t read_ret = (*NACL_VTBL(NaClDesc, descriptor)->PRead)(
-      descriptor, &data->ehdr, sizeof(data->ehdr), 0);
+  ssize_t read_ret = (*NACL_VTBL(NaClDesc, descriptor)->Read)(

[Mark Seaborn, 2014/03/28 01:38:25]

Julien and I are both OK with allowing the pread() syscall, so you can leave
this as it was and change the BPF policy.

[hamaji, 2014/03/28 12:06:10]

OK, I'd remove this change.

+      descriptor, &data->ehdr, sizeof(data->ehdr));
   if (NaClSSizeIsNegErrno(&read_ret) ||
       static_cast<size_t>(read_ret) != sizeof(data->ehdr)) {
     LOG(ERROR) << "Could not load elf headers.";
     return LOAD_READ_ERROR;
   }
 
   NaClErrorCode error_code = ValidateElfHeader(data->ehdr);
   if (error_code != LOAD_OK)
     return error_code;
 
   // Read program headers.
   if (data->ehdr.e_phnum > Data::MAX_PROGRAM_HEADERS) {
     LOG(ERROR) << "Too many program headers";
     return LOAD_TOO_MANY_PROG_HDRS;
   }
 
   if (data->ehdr.e_phentsize != sizeof(data->phdrs[0])) {
     LOG(ERROR) << "Bad program headers size\n"
                << "  ehdr_.e_phentsize = " << data->ehdr.e_phentsize << "\n"
                << "  sizeof phdrs[0] = " << sizeof(data->phdrs[0]);
     return LOAD_BAD_PHENTSIZE;
   }
 
+  // We avoid the use of pread here to reduce the number of required
+  // syscalls for non-SFI mode.
+  off_t ret = (*NACL_VTBL(NaClDesc, descriptor)->Seek)(
+      descriptor, data->ehdr.e_phoff, SEEK_SET);
+  if (ret != static_cast<off_t>(data->ehdr.e_phoff)) {
+    LOG(ERROR) << "Cannot load prog headers";
+    return LOAD_READ_ERROR;
+  }
+
   size_t read_size = data->ehdr.e_phnum * data->ehdr.e_phentsize;
-  read_ret = (*NACL_VTBL(NaClDesc, descriptor)->PRead)(
-      descriptor, data->phdrs, read_size, data->ehdr.e_phoff);
+  read_ret = (*NACL_VTBL(NaClDesc, descriptor)->Read)(
+      descriptor, data->phdrs, read_size);
 
   if (NaClSSizeIsNegErrno(&read_ret) ||
       static_cast<size_t>(read_ret) != read_size) {
     LOG(ERROR) << "Cannot load prog headers";
     return LOAD_READ_ERROR;
   }
 
   data_.swap(data);
   return LOAD_OK;
 }
@@ skipping 16 matching lines @@
   if (error != LOAD_OK) {
     LOG(ERROR) << "ElfImage::Load: Failed to load segments";
     return error;
   }
 
   return LOAD_OK;
 }
 
 }  // namespace nonsfi
 }  // namespace nacl