Re: Crash while determining coding system
On Thu, Mar 27, 2014 at 9:18 AM, Jerry James <james(a)xemacs.org> wrote:
[Originally sent 19 Mar 2014, but I haven't seen it show up in
the
archives.]
I just received a bug report for the Fedora build of XEmacs:
https://bugzilla.redhat.com/show_bug.cgi?id=1078159
What seems to have happened is that determine_real_coding_system
(file-coding.c) was called, and tried to read some data from the lstream.
However, Lstream_read encountered an error of some kind, I don't know
what. This resulted in an empty buffer, and nread == -1. We then
proceeded to pass the empty buffer and the count of -1 to
detect_coding_type, which used the count of -1 to justify walking off the
end of allocated memory, thereby triggering a segfault.
We need to notice the Lstream_read failure and bail out of
determine_real_coding_system. I'm not entirely sure of the right way to do
that. If one of you coding system master could suggest something, I'd
appreciate it.
Would something like this be appropriate?
diff -r 9fae6227ede5 src/ChangeLog
--- a/src/ChangeLog Thu Mar 27 08:59:03 2014 -0600
+++ b/src/ChangeLog Thu Mar 27 09:32:53 2014 -0600
＠＠ -1,3 +1,10 ＠＠
+2014-03-27 Jerry James <james(a)xemacs.org>
+
+ * file-coding.c (encode_decode_coding_region): Bail out if
+ Lstream_read encounters an error (returns -1).
+ (determine_real_coding_system): Ditto.
+ (Ffind_coding_system_magic_cookie_in_file): Ditto.
+
2014-01-27 Michael Sperber <mike(a)xemacs.org>
* symbols.c (Fdefine_function): Allow optional `docstring'
diff -r 9fae6227ede5 src/file-coding.c
--- a/src/file-coding.c Thu Mar 27 08:59:03 2014 -0600
+++ b/src/file-coding.c Thu Mar 27 09:32:53 2014 -0600
＠＠ -2294,7 +2294,7 ＠＠
Bytecount size_in_bytes =
Lstream_read (istr, tempbuf, sizeof (tempbuf));
- if (!size_in_bytes)
+ if (size_in_bytes <= 0)
break;
newpos = lisp_buffer_stream_startpos (istr);
Lstream_write (ostr, tempbuf, size_in_bytes);
＠＠ -3863,24 +3863,32 ＠＠
make_opaque_ptr (st));
UExtbyte buf[4096];
Bytecount nread = Lstream_read (stream, buf, sizeof (buf));
- Lisp_Object coding_system
- = look_for_coding_system_magic_cookie (buf, nread, 1);
-
- if (NILP (coding_system))
+ Lisp_Object coding_system;
+
+ if (nread > 0)
{
- while (1)
+ coding_system = look_for_coding_system_magic_cookie (buf, nread, 1);
+
+ if (NILP (coding_system))
{
- if (detect_coding_type (st, buf, nread))
- break;
- nread = Lstream_read (stream, buf, sizeof (buf));
- if (nread == 0)
- break;
+ while (1)
+ {
+ if (detect_coding_type (st, buf, nread))
+ break;
+ nread = Lstream_read (stream, buf, sizeof (buf));
+ if (nread <= 0)
+ break;
+ }
+
+ coding_system = detected_coding_system (st);
}
- coding_system = detected_coding_system (st);
+ Lstream_rewind (stream);
}
-
- Lstream_rewind (stream);
+ else
+ {
+ coding_system = Qnil;
+ }
unbind_to (depth);
return coding_system;
＠＠ -4315,7 +4323,9 ＠＠
Lstream_delete (XLSTREAM (lstream));
retry_close (fd);
- return look_for_coding_system_magic_cookie (buf, nread, 0);
+ return (nread > 0)
+ ? look_for_coding_system_magic_cookie (buf, nread, 0)
+: Qnil;
}
--
Jerry James
http://www.jamezone.org/
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