commit 19e878017a16456274298398c54850e9c7b9ba1e
author David Anderson <dvander@google.com> Wed Feb 26 14:59:08 2020 -0800
committer David Anderson <dvander@google.com> Tue Mar 03 18:59:10 2020 -0800
tree bbfc1ab41e760a0281192f33306c9ffa41624473
parent 63cd13fbdfea8cc2c4e6e274410846b37edf47db

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

fs_mgr/libdm/dm.cpp

diff --git a/fs_mgr/libdm/dm.cpp b/fs_mgr/libdm/dm.cpp
index 254fbed..673e145 100644
--- a/fs_mgr/libdm/dm.cpp
+++ b/fs_mgr/libdm/dm.cpp
@@ -120,7 +120,7 @@
         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 @@
         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

diff --git a/fs_mgr/libdm/utility.cpp b/fs_mgr/libdm/utility.cpp
index f252565..0eb59ab 100644
--- a/fs_mgr/libdm/utility.cpp
+++ b/fs_mgr/libdm/utility.cpp
@@ -19,6 +19,8 @@
 
 #include <thread>
 
+#include <android-base/logging.h>
+
 using namespace std::literals;
 
 namespace android {
@@ -45,7 +47,11 @@
         // 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 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);