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Fix config file parsing on musl libc

On the musl libc, autorun, layout and workspace name settings were
always rejected as invalid. As it turns out, parsing those was relying
on sscanf incorrectly matching %Nc as long as there is at least one
character. This is fixed by matching only the initial part of the string
via sscanf and skipping ahead by the amount of bytes consumed. This also
avoids unnecessary zeroing, copying and possible implicit truncation.

Relevant glibc bug:
https://sourceware.org/bugzilla/show_bug.cgi?id=12701
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mvf authored and LordReg committed Mar 23, 2018
1 parent b34cb01 commit 1291a720e10e9c814c3e8fd17d2e4fd3bc9c99c8
Showing with 27 additions and 26 deletions.
  1. +27 −26 spectrwm.c
@@ -8923,8 +8923,8 @@ int
setconfvalue(const char *selector, const char *value, int flags)
{
struct workspace *ws;
int i, ws_id, num_screens;
char *b, *str, *sp, s[1024];
int i, ws_id, num_screens, n;
char *b, *str, *sp;
switch (flags) {
case SWM_S_BAR_ACTION:
@@ -9148,9 +9148,11 @@ setconfvalue(const char *selector, const char *value, int flags)
if (getenv("SWM_STARTED") != NULL)
return (0);
bzero(s, sizeof s);
if (sscanf(value, "ws[%d]:%1023c", &ws_id, s) != 2)
n = 0;
if (sscanf(value, "ws[%d]:%n", &ws_id, &n) != 1 || n == 0 ||
value[n] == '\0')
errx(1, "invalid entry, should be 'ws[<idx>]:name'");
value += n;
ws_id--;
if (ws_id < 0 || ws_id >= workspace_limit)
errx(1, "setconfvalue: workspace_name: invalid "
@@ -9160,14 +9162,12 @@ setconfvalue(const char *selector, const char *value, int flags)
for (i = 0; i < num_screens; ++i) {
ws = (struct workspace *)&screens[i].ws;
if (strlen(s) > 0) {
free(ws[ws_id].name);
if ((ws[ws_id].name = strdup(s)) == NULL)
err(1, "setconfvalue: workspace_name.");
free(ws[ws_id].name);
if ((ws[ws_id].name = strdup(value)) == NULL)
err(1, "setconfvalue: workspace_name.");
ewmh_update_desktop_names();
ewmh_get_desktop_names();
}
ewmh_update_desktop_names();
ewmh_get_desktop_names();
}
break;
default:
@@ -9271,10 +9271,9 @@ int
setautorun(const char *selector, const char *value, int flags)
{
int ws_id;
char s[1024];
char *ap, *sp, *str;
union arg a;
int argc = 0;
int argc = 0, n;
pid_t pid;
struct pid_e *p;
@@ -9285,14 +9284,16 @@ setautorun(const char *selector, const char *value, int flags)
if (getenv("SWM_STARTED"))
return (0);
bzero(s, sizeof s);
if (sscanf(value, "ws[%d]:%1023c", &ws_id, s) != 2)
n = 0;
if (sscanf(value, "ws[%d]:%n", &ws_id, &n) != 1 || n == 0 ||
value[n] == '\0')
errx(1, "invalid autorun entry, should be 'ws[<idx>]:command'");
value += n;
ws_id--;
if (ws_id < 0 || ws_id >= workspace_limit)
errx(1, "autorun: invalid workspace %d", ws_id + 1);
sp = str = expand_tilde((char *)&s);
sp = str = expand_tilde(value);
/*
* This is a little intricate
@@ -9343,9 +9344,8 @@ int
setlayout(const char *selector, const char *value, int flags)
{
struct workspace *ws;
int ws_id, i, x, mg, ma, si, ar;
int ws_id, i, x, mg, ma, si, ar, n;
int st = SWM_V_STACK, num_screens;
char s[1024];
bool f = false;
/* suppress unused warnings since vars are needed */
@@ -9355,27 +9355,28 @@ setlayout(const char *selector, const char *value, int flags)
if (getenv("SWM_STARTED"))
return (0);
bzero(s, sizeof s);
if (sscanf(value, "ws[%d]:%d:%d:%d:%d:%1023c",
&ws_id, &mg, &ma, &si, &ar, s) != 6)
n = 0;
if (sscanf(value, "ws[%d]:%d:%d:%d:%d:%n",
&ws_id, &mg, &ma, &si, &ar, &n) != 5 || n == 0 || value[n] == '\0')
errx(1, "invalid layout entry, should be 'ws[<idx>]:"
"<master_grow>:<master_add>:<stack_inc>:<always_raise>:"
"<type>'");
value += n;
ws_id--;
if (ws_id < 0 || ws_id >= workspace_limit)
errx(1, "layout: invalid workspace %d", ws_id + 1);
if (strcasecmp(s, "vertical") == 0)
if (strcasecmp(value, "vertical") == 0)
st = SWM_V_STACK;
else if (strcasecmp(s, "vertical_flip") == 0) {
else if (strcasecmp(value, "vertical_flip") == 0) {
st = SWM_V_STACK;
f = true;
} else if (strcasecmp(s, "horizontal") == 0)
} else if (strcasecmp(value, "horizontal") == 0)
st = SWM_H_STACK;
else if (strcasecmp(s, "horizontal_flip") == 0) {
else if (strcasecmp(value, "horizontal_flip") == 0) {
st = SWM_H_STACK;
f = true;
} else if (strcasecmp(s, "fullscreen") == 0)
} else if (strcasecmp(value, "fullscreen") == 0)
st = SWM_MAX_STACK;
else
errx(1, "invalid layout entry, should be 'ws[<idx>]:"

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