Don't report partialResult errors from sendfile

The input file descriptor is always a regular file, so sendfile can't lose any
data if it will not be able to write them to the output file descriptor.

Reported-by: syzbot+22d22330a35fa1c02155@syzkaller.appspotmail.com
PiperOrigin-RevId: 272730357

2 files changed, 20 insertions, 0 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index b555bd7aa..b9fee9ee9 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -1905,6 +1905,7 @@ cc_binary(
     srcs = ["sendfile.cc"],
     linkstatic = 1,
     deps = [
+        "//test/util:eventfd_util",
         "//test/util:file_descriptor",
         "//test/util:temp_path",
         "//test/util:test_main",
diff --git a/test/syscalls/linux/sendfile.cc b/test/syscalls/linux/sendfile.cc
index 4502e7fb4..580ab5193 100644
--- a/test/syscalls/linux/sendfile.cc
+++ b/test/syscalls/linux/sendfile.cc
@@ -13,6 +13,7 @@
 // limitations under the License.
 
 #include <fcntl.h>
+#include <sys/eventfd.h>
 #include <sys/sendfile.h>
 #include <unistd.h>
 
@@ -21,6 +22,7 @@
 #include "absl/strings/string_view.h"
 #include "absl/time/clock.h"
 #include "absl/time/time.h"
+#include "test/util/eventfd_util.h"
 #include "test/util/file_descriptor.h"
 #include "test/util/temp_path.h"
 #include "test/util/test_util.h"
@@ -511,6 +513,23 @@ TEST(SendFileTest, SendPipeBlocks) {
               SyscallSucceedsWithValue(kDataSize));
 }
 
+TEST(SendFileTest, SendToSpecialFile) {
+  // Create temp file.
+  const TempPath in_file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFileWith(
+      GetAbsoluteTestTmpdir(), "", TempPath::kDefaultFileMode));
+
+  const FileDescriptor inf =
+      ASSERT_NO_ERRNO_AND_VALUE(Open(in_file.path(), O_RDWR));
+  constexpr int kSize = 0x7ff;
+  ASSERT_THAT(ftruncate(inf.get(), kSize), SyscallSucceeds());
+
+  auto eventfd = ASSERT_NO_ERRNO_AND_VALUE(NewEventFD());
+
+  // eventfd can accept a number of bytes which is a multiple of 8.
+  EXPECT_THAT(sendfile(eventfd.get(), inf.get(), nullptr, 0xfffff),
+              SyscallSucceedsWithValue(kSize & (~7)));
+}
+
 }  // namespace
 
 }  // namespace testing