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libdm: Fix WaitForFile early-returning on failed accesses.

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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
This commit is contained in:
David Anderson 2020-02-26 14:59:08 -08:00
parent 7e5f2aa478
commit 44ae546061
2 changed files with 14 additions and 4 deletions
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4
fs_mgr/libdm/dm.cpp
View file

@ -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;
}

14
fs_mgr/libdm/utility.cpp
View file

@ -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);