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gdbstub: Reject invalid RLE repeat counts

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"Debugging with GDB / Appendix E GDB Remote Serial Protocol /
Overview" specifies "The printable characters '#' and '$' or with a
numeric value greater than 126 must not be used."  gdb_read_byte()
only rejects values < 32.  This is wrong.  Impact depends on the caller:

* gdb_handlesig() passes a char.  Incorrectly accepts '#', '$' and
  '\127'.

* gdb_chr_receive() passes an uint8_t.  Additionally accepts
  characters with the most-significant bit set.

Correct the validity check to match the specification.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190514180311.16028-4-armbru@redhat.com>
This commit is contained in:
Markus Armbruster 2019-05-14 20:03:08 +02:00
parent d18dc3af47
commit 046aba169b
1 changed files with 5 additions and 1 deletions
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6
gdbstub.c
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@ -2064,7 +2064,11 @@ static void gdb_read_byte(GDBState *s, int ch)
}
break;
case RS_GETLINE_RLE:
if (ch < ' ') {
/*
* Run-length encoding is explained in "Debugging with GDB /
* Appendix E GDB Remote Serial Protocol / Overview".
*/
if (ch < ' ' || ch == '#' || ch == '$' || ch > 126) {
/* invalid RLE count encoding */
trace_gdbstub_err_invalid_repeat((uint8_t)ch);
s->state = RS_GETLINE;