1 files changed, 13 insertions, 7 deletions

diff --git a/src/process.c b/src/process.c
index 814fbc4a747..d76cebe5e12 100644
--- a/src/process.c
+++ b/src/process.c
@@ -2855,13 +2855,19 @@ read_process_output (proc, channel)
       carryover = nbytes - coding->consumed;
       if (carryover > 0)
         {
-          /* We must move the data carried over to the tail of
-             decoding buffer.  We are sure that the size of decoding
-             buffer (decided by decoding_buffer_size) is large enough
-             to contain them.  */
-          bcopy (chars + nbytes - carryover,
-                 (XSTRING (p->decoding_buf)->data
-                  + STRING_BYTES (XSTRING (p->decoding_buf)) - carryover),
+          /* Copy the carryover bytes to the end of p->decoding_buf, to
+             be processed on the next read.  Since decoding_buffer_size
+             asks for an extra amount of space beyond the maximum
+             expected for the output, there should always be sufficient
+             space for the carryover (which is by definition a sequence
+             of bytes that was not long enough to be decoded, and thus
+             has a bounded length).  */
+          if (STRING_BYTES (XSTRING (p->decoding_buf))
+              < coding->produced + carryover)
+            abort ();
+          bcopy (chars + coding->consumed,
+                 XSTRING (p->decoding_buf)->data
+                 + STRING_BYTES (XSTRING (p->decoding_buf)) - carryover,
                  carryover);
           XSETINT (p->decoding_carryover, carryover);
         }