From 6e5d7f393ed899c8e980b238be3cf23ec296e3f6 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Wed, 29 Oct 2014 11:57:03 +0000 Subject: [PATCH] Fix uninitialized value access when very first GDB command entered is While running GDB under Valgrind, I noticed that if the very first command entered is just , GDB accesses an uninitialized value: $ valgrind ./gdb -q -nx ==26790== Memcheck, a memory error detector ==26790== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al. ==26790== Using Valgrind-3.9.0 and LibVEX; rerun with -h for copyright info ==26790== Command: ./gdb -q -nx ==26790== (gdb) ==26790== Conditional jump or move depends on uninitialised value(s) ==26790== at 0x619DFC: command_line_handler (event-top.c:588) ==26790== by 0x7813D5: rl_callback_read_char (callback.c:220) ==26790== by 0x6194B4: rl_callback_read_char_wrapper (event-top.c:166) ==26790== by 0x61988A: stdin_event_handler (event-top.c:372) ==26790== by 0x61847D: handle_file_event (event-loop.c:762) ==26790== by 0x617964: process_event (event-loop.c:339) ==26790== by 0x617A2B: gdb_do_one_event (event-loop.c:403) ==26790== by 0x617A7B: start_event_loop (event-loop.c:428) ==26790== by 0x6194E6: cli_command_loop (event-top.c:181) ==26790== by 0x60F86B: current_interp_command_loop (interps.c:317) ==26790== by 0x610A34: captured_command_loop (main.c:321) ==26790== by 0x60C728: catch_errors (exceptions.c:237) ==26790== (gdb) It's this check here: /* If we just got an empty line, and that is supposed to repeat the previous command, return the value in the global buffer. */ if (repeat && p == linebuffer && *p != '\\') { The problem is that linebuffer's contents were never initialized at this point. gdb/ 2014-10-29 Pedro Alves * event-top.c (command_line_handler): Clear the first byte of linebuffer, when it is first allocated. --- gdb/ChangeLog | 5 +++++ gdb/event-top.c | 1 + 2 files changed, 6 insertions(+) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 1125b1e9101..58a7e982a12 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2014-10-29 Pedro Alves + + * event-top.c (command_line_handler): Clear the first byte of + linebuffer, when it is first allocated. + 2014-10-29 Pedro Alves * tui/tui.c (tui_rl_switch_mode): Wrap tui_enable/tui_disable in diff --git a/gdb/event-top.c b/gdb/event-top.c index 3f9deec2c23..f539733637f 100644 --- a/gdb/event-top.c +++ b/gdb/event-top.c @@ -467,6 +467,7 @@ command_line_handler (char *rl) { linelength = 80; linebuffer = (char *) xmalloc (linelength); + linebuffer[0] = '\0'; } p = linebuffer; -- 2.30.2