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Commit 44ae5460 authored by David Anderson's avatar David Anderson
Browse files

libdm: Fix WaitForFile early-returning on failed accesses. 

WaitForFile/WaitForDeletedFile both early return true if an error like
EPERM occurs. This was intentional because the code was modeled off
earlier fs_mgr code, but it makes libdm inherently racy if sepolicy is
not configured correctly. It's better to have these result in explicit
and consistent failures.

Bug: 148103327
Test: fastboot flashall
Change-Id: I0c78818962e1db91b556e523c418db28f7d78fae
Merged-In: I0c78818962e1db91b556e523c418db28f7d78fae
parent 7e5f2aa4

fs_mgr/libdm/dm.cpp

+2 −2
Original line number Diff line number Diff line
@@ -120,7 +120,7 @@ bool DeviceMapper::DeleteDevice(const std::string& name, 
        return false;

    }

    if (!WaitForFileDeleted(unique_path, timeout_ms)) {

        LOG(ERROR) << "Timeout out waiting for " << unique_path << " to be deleted";

        LOG(ERROR) << "Failed waiting for " << unique_path << " to be deleted";

        return false;

    }

    return true;
@@ -161,7 +161,7 @@ bool DeviceMapper::CreateDevice(const std::string& name, const DmTable& table, s 
        return true;

    }

    if (!WaitForFile(unique_path, timeout_ms)) {

        LOG(ERROR) << "Timed out waiting for device path: " << unique_path;

        LOG(ERROR) << "Failed waiting for device path: " << unique_path;

        DeleteDevice(name);

        return false;

    }

fs_mgr/libdm/utility.cpp

+12 −2
Original line number Diff line number Diff line
@@ -19,6 +19,8 @@ 


#include <thread>



#include <android-base/logging.h>



using namespace std::literals;



namespace android {
@@ -45,7 +47,11 @@ bool WaitForFile(const std::string& path, const std::chrono::milliseconds& timeo 
        // If the file exists but returns EPERM or something, we consider the

        // condition met.

        if (access(path.c_str(), F_OK) != 0) {

            if (errno == ENOENT) return WaitResult::Wait;

            if (errno == ENOENT) {

                return WaitResult::Wait;

            }

            PLOG(ERROR) << "access failed: " << path;

            return WaitResult::Fail;

        }

        return WaitResult::Done;

    };
@@ -54,9 +60,13 @@ bool WaitForFile(const std::string& path, const std::chrono::milliseconds& timeo 


bool WaitForFileDeleted(const std::string& path, const std::chrono::milliseconds& timeout_ms) {

    auto condition = [&]() -> WaitResult {

        if (access(path.c_str(), F_OK) == 0 || errno != ENOENT) {

        if (access(path.c_str(), F_OK) == 0) {

            return WaitResult::Wait;

        }

        if (errno != ENOENT) {

            PLOG(ERROR) << "access failed: " << path;

            return WaitResult::Fail;

        }

        return WaitResult::Done;

    };

    return WaitForCondition(condition, timeout_ms);