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Speculatively fix crash in PrintBackendWin::EnumeratePrinters().

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Make sure Win32 EnumPrinters() failed with ERROR_INSUFFICIENT_BUFFER
before using values it provided. If EnumPrinters() failed for any other
reason, it may be providing garbage values.

Bug: 1285814
Change-Id: I8cedda6534040351c953a7b7c7db2c15de01e1d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3378045
Reviewed-by: Alan Screen <awscreen@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#961092}
This commit is contained in:
Lei Zhang
2022-01-19 20:04:16 +00:00
committed by Chromium LUCI CQ
parent 4fc268aea4
commit 2a6a9a8b72
1 changed files with 14 additions and 14 deletions

28
printing/backend/print_backend_win.cc

@ -209,28 +209,28 @@ mojom::ResultCode PrintBackendWin::EnumeratePrinters(
DCHECK(printer_list);
DWORD bytes_needed = 0;
DWORD count_returned = 0;
constexpr DWORD kFlags = PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS;
const DWORD kLevel = 4;
EnumPrinters(PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS, nullptr, kLevel,
nullptr, 0, &bytes_needed, &count_returned);
if (bytes_needed == 0) {
// No bytes needed could mean the operation failed or that there are simply
// no printer drivers installed. Rely upon system error code to
// distinguish between these.
logging::SystemErrorCode code = logging::GetLastSystemErrorCode();
if (code == ERROR_SUCCESS) {
VLOG(1) << "Found no printers";
return mojom::ResultCode::kSuccess;
}
EnumPrinters(kFlags, nullptr, kLevel, nullptr, 0, &bytes_needed,
&count_returned);
logging::SystemErrorCode code = logging::GetLastSystemErrorCode();
if (code == ERROR_SUCCESS) {
// If EnumPrinters() succeeded, that means there are no printer drivers
// installed because 0 bytes was sufficient.
DCHECK_EQ(bytes_needed, 0u);
VLOG(1) << "Found no printers";
return mojom::ResultCode::kSuccess;
}
if (code != ERROR_INSUFFICIENT_BUFFER) {
LOG(ERROR) << "Error enumerating printers: "
<< logging::SystemErrorCodeToString(code);
return GetResultCodeFromSystemErrorCode(code);
}
auto printer_info_buffer = std::make_unique<BYTE[]>(bytes_needed);
if (!EnumPrinters(PRINTER_ENUM_LOCAL | PRINTER_ENUM_CONNECTIONS, nullptr,
kLevel, printer_info_buffer.get(), bytes_needed,
&bytes_needed, &count_returned)) {
if (!EnumPrinters(kFlags, nullptr, kLevel, printer_info_buffer.get(),
bytes_needed, &bytes_needed, &count_returned)) {
NOTREACHED();
return GetResultCodeFromSystemErrorCode(logging::GetLastSystemErrorCode());
}