Handle utimes correctly for shared gofer filesystems.

Determine system time from within the sentry rather than relying on the remote
filesystem to prevent inconsistencies.
Resolve related TODOs; the time discrepancies in question don't exist anymore.

PiperOrigin-RevId: 305557099

2 files changed, 15 insertions, 19 deletions

diff --git a/pkg/sentry/fs/gofer/util.go b/pkg/sentry/fs/gofer/util.go
index 2d8d3a2ea..47a6c69bf 100644
--- a/pkg/sentry/fs/gofer/util.go
+++ b/pkg/sentry/fs/gofer/util.go
@@ -20,17 +20,29 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
+	ktime "gvisor.dev/gvisor/pkg/sentry/kernel/time"
 )
 
 func utimes(ctx context.Context, file contextFile, ts fs.TimeSpec) error {
 	if ts.ATimeOmit && ts.MTimeOmit {
 		return nil
 	}
+
+	// Replace requests to use the "system time" with the current time to
+	// ensure that timestamps remain consistent with the remote
+	// filesystem.
+	now := ktime.NowFromContext(ctx)
+	if ts.ATimeSetSystemTime {
+		ts.ATime = now
+	}
+	if ts.MTimeSetSystemTime {
+		ts.MTime = now
+	}
 	mask := p9.SetAttrMask{
 		ATime:              !ts.ATimeOmit,
-		ATimeNotSystemTime: !ts.ATimeSetSystemTime,
+		ATimeNotSystemTime: true,
 		MTime:              !ts.MTimeOmit,
-		MTimeNotSystemTime: !ts.MTimeSetSystemTime,
+		MTimeNotSystemTime: true,
 	}
 	as, ans := ts.ATime.Unix()
 	ms, mns := ts.MTime.Unix()
diff --git a/test/syscalls/linux/utimes.cc b/test/syscalls/linux/utimes.cc
index 3a927a430..22e6d1a85 100644
--- a/test/syscalls/linux/utimes.cc
+++ b/test/syscalls/linux/utimes.cc
@@ -34,17 +34,10 @@ namespace testing {
 
 namespace {
 
-// TODO(b/36516566): utimes(nullptr) does not pick the "now" time in the
-// application's time domain, so when asserting that times are within a window,
-// we expand the window to allow for differences between the time domains.
-constexpr absl::Duration kClockSlack = absl::Milliseconds(100);
-
 // TimeBoxed runs fn, setting before and after to (coarse realtime) times
 // guaranteed* to come before and after fn started and completed, respectively.
 //
 // fn may be called more than once if the clock is adjusted.
-//
-// * See the comment on kClockSlack. gVisor breaks this guarantee.
 void TimeBoxed(absl::Time* before, absl::Time* after,
                std::function<void()> const& fn) {
   do {
@@ -69,12 +62,6 @@ void TimeBoxed(absl::Time* before, absl::Time* after,
       // which could lead to test failures, but that is very unlikely to happen.
       continue;
     }
-
-    if (IsRunningOnGvisor()) {
-      // See comment on kClockSlack.
-      *before -= kClockSlack;
-      *after += kClockSlack;
-    }
   } while (*after < *before);
 }
 
@@ -235,10 +222,7 @@ void TestUtimensat(int dirFd, std::string const& path) {
   EXPECT_GE(mtime3, before);
   EXPECT_LE(mtime3, after);
 
-  if (!IsRunningOnGvisor()) {
-    // FIXME(b/36516566): Gofers set atime and mtime to different "now" times.
-    EXPECT_EQ(atime3, mtime3);
-  }
+  EXPECT_EQ(atime3, mtime3);
 }
 
 TEST(UtimensatTest, OnAbsPath) {