swayfx/sway/commands/bar.c
Michael Weiser 730efbc89c Prevent use-after-free on first bar subcommand error
If any error is encountered during execution of the first subcommand of
a freshly created bar configuration, parsing apparently is to be aborted
and the current bar config is freed. The pointer to that memory is left
dangling though, leading to a use-after-free on successive bar
subcommands. This quite reliably ends in a crash like so:

sway -c reproducer.config
00:00:00.083 [sway/config.c:865] Error on line 2 'foo bar': Unknown/invalid command 'foo' (s)
free(): double free detected in tcache 2
00:00:00.608 [swaynag/swaynag.c:451] failed to register with the wayland display
Aborted (core dumped)

Minimal reproducer config:
bar {
        foo bar
        position top
}

Other messages:
malloc(): unaligned fastbin chunk detected
double free or corruption (fasttop)

The invalid command has to be the first for a newly created bar config.
Removing the command or switching order so it's not the first one masks
the problem.

Prevent this from occuring by resetting the pointer to NULL after
freeing the memory.

Signed-off-by: Michael Weiser <michael.weiser@gmx.de>
2021-04-18 20:53:36 -07:00

139 lines
4.1 KiB
C

#define _POSIX_C_SOURCE 200809
#include <stdio.h>
#include <string.h>
#include <strings.h>
#include "sway/commands.h"
#include "sway/config.h"
#include "sway/ipc-server.h"
#include "log.h"
// Must be in alphabetical order for bsearch
static const struct cmd_handler bar_handlers[] = {
{ "bindcode", bar_cmd_bindcode },
{ "binding_mode_indicator", bar_cmd_binding_mode_indicator },
{ "bindsym", bar_cmd_bindsym },
{ "colors", bar_cmd_colors },
{ "font", bar_cmd_font },
{ "gaps", bar_cmd_gaps },
{ "height", bar_cmd_height },
{ "hidden_state", bar_cmd_hidden_state },
{ "icon_theme", bar_cmd_icon_theme },
{ "mode", bar_cmd_mode },
{ "modifier", bar_cmd_modifier },
{ "output", bar_cmd_output },
{ "pango_markup", bar_cmd_pango_markup },
{ "position", bar_cmd_position },
{ "separator_symbol", bar_cmd_separator_symbol },
{ "status_command", bar_cmd_status_command },
{ "status_edge_padding", bar_cmd_status_edge_padding },
{ "status_padding", bar_cmd_status_padding },
{ "strip_workspace_name", bar_cmd_strip_workspace_name },
{ "strip_workspace_numbers", bar_cmd_strip_workspace_numbers },
{ "tray_bindcode", bar_cmd_tray_bindcode },
{ "tray_bindsym", bar_cmd_tray_bindsym },
{ "tray_output", bar_cmd_tray_output },
{ "tray_padding", bar_cmd_tray_padding },
{ "unbindcode", bar_cmd_unbindcode },
{ "unbindsym", bar_cmd_unbindsym },
{ "workspace_buttons", bar_cmd_workspace_buttons },
{ "workspace_min_width", bar_cmd_workspace_min_width },
{ "wrap_scroll", bar_cmd_wrap_scroll },
};
// Must be in alphabetical order for bsearch
static const struct cmd_handler bar_config_handlers[] = {
{ "id", bar_cmd_id },
{ "swaybar_command", bar_cmd_swaybar_command },
};
// Determines whether the subcommand is valid in any bar handler struct
static bool is_subcommand(char *name) {
return find_handler(name, bar_handlers, sizeof(bar_handlers)) ||
find_handler(name, bar_config_handlers, sizeof(bar_config_handlers));
}
struct cmd_results *cmd_bar(int argc, char **argv) {
struct cmd_results *error = NULL;
if ((error = checkarg(argc, "bar", EXPECTED_AT_LEAST, 2))) {
return error;
}
char *id = NULL;
if (strcmp(argv[0], "id") != 0 && is_subcommand(argv[1])) {
for (int i = 0; i < config->bars->length; ++i) {
struct bar_config *item = config->bars->items[i];
if (strcmp(item->id, argv[0]) == 0) {
sway_log(SWAY_DEBUG, "Selecting bar: %s", argv[0]);
config->current_bar = item;
break;
}
}
if (!config->current_bar) {
id = strdup(argv[0]);
}
++argv; --argc;
} else if (config->reading && !config->current_bar) {
int len = snprintf(NULL, 0, "bar-%d", config->bars->length) + 1;
id = malloc(len * sizeof(char));
if (!id) {
return cmd_results_new(CMD_FAILURE, "Unable to allocate bar id");
}
snprintf(id, len, "bar-%d", config->bars->length);
} else if (!config->reading && strcmp(argv[0], "mode") != 0 &&
strcmp(argv[0], "hidden_state") != 0) {
if (is_subcommand(argv[0])) {
return cmd_results_new(CMD_INVALID, "No bar defined.");
} else {
return cmd_results_new(CMD_INVALID,
"Unknown/invalid command '%s'", argv[1]);
}
}
if (id) {
sway_log(SWAY_DEBUG, "Creating bar: %s", id);
config->current_bar = default_bar_config();
if (!config->current_bar) {
free(id);
return cmd_results_new(CMD_FAILURE, "Unable to allocate bar config");
}
config->current_bar->id = id;
}
struct cmd_results *res = NULL;
if (find_handler(argv[0], bar_config_handlers,
sizeof(bar_config_handlers))) {
if (config->reading) {
res = config_subcommand(argv, argc, bar_config_handlers,
sizeof(bar_config_handlers));
} else {
res = cmd_results_new(CMD_INVALID,
"Can only be used in the config file");
}
} else {
res = config_subcommand(argv, argc, bar_handlers, sizeof(bar_handlers));
}
if (res && res->status != CMD_SUCCESS) {
if (id) {
free_bar_config(config->current_bar);
config->current_bar = NULL;
id = NULL;
}
return res;
}
if (id) {
list_add(config->bars, config->current_bar);
}
if (!config->reading && config->current_bar) {
ipc_event_barconfig_update(config->current_bar);
if (id) {
load_swaybar(config->current_bar);
}
config->current_bar = NULL;
}
return res;
}