[syserr] Fix SIGBUS on syserr.FromError

Fix syzcaller panic SIGBUS on error handling. Done by
adding an interface, errors.GuestError, which errors can
implement in order to be compared against each other.

PiperOrigin-RevId: 393867554

2 files changed, 18 insertions, 0 deletions

diff --git a/test/syscalls/linux/BUILD b/test/syscalls/linux/BUILD
index 01ee432cb..b06b3d233 100644
--- a/test/syscalls/linux/BUILD
+++ b/test/syscalls/linux/BUILD
@@ -3293,9 +3293,12 @@ cc_library(
     ],
     deps = [
         ":unix_domain_socket_test_util",
+        "//test/util:file_descriptor",
+        "//test/util:memory_util",
         "//test/util:socket_util",
         "@com_google_absl//absl/strings",
         gtest,
+        "//test/util:temp_path",
         "//test/util:test_util",
         "//test/util:thread_util",
     ],
diff --git a/test/syscalls/linux/socket_unix.cc b/test/syscalls/linux/socket_unix.cc
index cf96b2075..43433eaae 100644
--- a/test/syscalls/linux/socket_unix.cc
+++ b/test/syscalls/linux/socket_unix.cc
@@ -27,7 +27,10 @@
 #include "gtest/gtest.h"
 #include "absl/strings/string_view.h"
 #include "test/syscalls/linux/unix_domain_socket_test_util.h"
+#include "test/util/file_descriptor.h"
+#include "test/util/memory_util.h"
 #include "test/util/socket_util.h"
+#include "test/util/temp_path.h"
 #include "test/util/test_util.h"
 #include "test/util/thread_util.h"
 
@@ -268,6 +271,18 @@ TEST_P(UnixSocketPairTest, SocketReopenFromProcfs) {
   }
 }
 
+// Repro for b/196804997.
+TEST_P(UnixSocketPairTest, SendFromMmapBeyondEof) {
+  TempPath file = ASSERT_NO_ERRNO_AND_VALUE(TempPath::CreateFile());
+  FileDescriptor fd = ASSERT_NO_ERRNO_AND_VALUE(Open(file.path(), O_RDONLY));
+  Mapping m = ASSERT_NO_ERRNO_AND_VALUE(
+      Mmap(nullptr, kPageSize, PROT_READ, MAP_SHARED, fd.get(), 0));
+
+  auto sockets = ASSERT_NO_ERRNO_AND_VALUE(NewSocketPair());
+  ASSERT_THAT(send(sockets->first_fd(), m.ptr(), m.len(), 0),
+              SyscallFailsWithErrno(EFAULT));
+}
+
 }  // namespace
 
 }  // namespace testing