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Commit abbd4a7a authored by Nicolas Geoffray's avatar Nicolas Geoffray
Browse files

Add checks to ensure only the ART memfd file is whitelisted.

A memfd file can be created with any name, but to protect ourselves
from unintended leakage, check that it's the name ART uses.

Test: boots
Bug: 119800099
Change-Id: Ibc684d09dd05f38933c6808b72fb402fc9d5e4eb
parent 813b9e8c
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+18 −6
Original line number Original line Diff line number Diff line
@@ -59,8 +59,8 @@ FileDescriptorWhitelist* FileDescriptorWhitelist::Get() {
  return instance_;
  return instance_;
}
}


static bool IsMemfd(const std::string& path) {
static bool IsArtMemfd(const std::string& path) {
  return android::base::StartsWith(path, "/memfd:");
  return android::base::StartsWith(path, "/memfd:/boot-image-methods.art");
}
}


bool FileDescriptorWhitelist::IsAllowed(const std::string& path) const {
bool FileDescriptorWhitelist::IsAllowed(const std::string& path) const {
@@ -91,8 +91,8 @@ bool FileDescriptorWhitelist::IsAllowed(const std::string& path) const {
    return true;
    return true;
  }
  }


  // In-memory files created through memfd_create are allowed.
  // the in-memory file created by ART through memfd_create is allowed.
  if (IsMemfd(path)) {
  if (IsArtMemfd(path)) {
    return true;
    return true;
  }
  }


@@ -321,8 +321,8 @@ void FileDescriptorInfo::ReopenOrDetach(fail_fn_t fail_fn) const {
    return DetachSocket(fail_fn);
    return DetachSocket(fail_fn);
  }
  }


  // Children can directly use in-memory files created through memfd_create.
  // Children can directly use the in-memory file created by ART through memfd_create.
  if (IsMemfd(file_path)) {
  if (IsArtMemfd(file_path)) {
    return;
    return;
  }
  }


@@ -545,6 +545,10 @@ FileDescriptorTable::FileDescriptorTable(
}
}


void FileDescriptorTable::RestatInternal(std::set<int>& open_fds, fail_fn_t fail_fn) {
void FileDescriptorTable::RestatInternal(std::set<int>& open_fds, fail_fn_t fail_fn) {
  // ART creates a file through memfd for optimization purposes. We make sure
  // there is at most one being created.
  bool art_memfd_seen = false;

  // Iterate through the list of file descriptors we've already recorded
  // Iterate through the list of file descriptors we've already recorded
  // and check whether :
  // and check whether :
  //
  //
@@ -577,6 +581,14 @@ void FileDescriptorTable::RestatInternal(std::set<int>& open_fds, fail_fn_t fail
        // FD.
        // FD.
      }
      }


      if (IsArtMemfd(it->second->file_path)) {
        if (art_memfd_seen) {
          fail_fn("ART fd already seen: " + it->second->file_path);
        } else {
          art_memfd_seen = true;
        }
      }

      ++it;
      ++it;


      // Finally, remove the FD from the set of open_fds. We do this last because
      // Finally, remove the FD from the set of open_fds. We do this last because