From 743abb8f305b4badcd0cb3480f812b68aa0b581a Mon Sep 17 00:00:00 2001
From: moto <855818+mthrok@users.noreply.github.com>
Date: Mon, 1 Feb 2021 16:00:33 +0000
Subject: [PATCH] Fix segfault by calling ftell instead of useing tell_off

---
 torchaudio/csrc/sox/effects_chain.cpp | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/torchaudio/csrc/sox/effects_chain.cpp b/torchaudio/csrc/sox/effects_chain.cpp
index 43cab58a7e..80885b296c 100644
--- a/torchaudio/csrc/sox/effects_chain.cpp
+++ b/torchaudio/csrc/sox/effects_chain.cpp
@@ -335,7 +335,17 @@ int fileobj_input_drain(sox_effect_t* effp, sox_sample_t* obuf, size_t* osamp) {
   //     |**********|-----------------|++++++++++++|
   //                ^ ftell
 
-  const auto num_consumed = sf->tell_off;
+  // NOTE:
+  //   Do not use `sf->tell_off` here. Presumably, `tell_off` and `fseek` are
+  //   supposed to be in sync, but there are cases (Vorbis) they are not
+  //   in sync and `tell_off` has seemingly uninitialized value, which
+  //   leads num_remain to be negative and cause segmentation fault
+  //   in `memmove`.
+  const auto num_consumed = ftell((FILE*)sf->fp);
+  if (num_consumed > priv->buffer_size) {
+    throw std::runtime_error("Internal Error: buffer overrun.");
+  }
+
   const auto num_remain = priv->buffer_size - num_consumed;
 
   // 1.1. Fetch the data to see if there is data to fill the buffer