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Overwrite tracked file descriptors when exporting COLORED_STDERR_FDS.

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If the list of tracked file descriptors is modified to contain unwanted
values (e.g. when a parent process closes or redirects stderr), this
makes it possible to set the tracked file descriptors back to a given
list.

This problem occurred with startx which somehow closes or redirects
stderr. As COLORED_STDERR_FDS was set in the shell running startx, this
disabled coloring stderr for all processes started in the X11 session.

This is no longer an issue. As COLORED_STDERR_FDS is set in the shell
configuration file, it automatically sets the list to the correct value
when a shell is opened in the terminal emulator once X11 is running.
This commit is contained in:
Simon Ruderich
2013-06-21 18:26:23 +02:00
parent 045ca46e79
commit 0d7f306898
8 changed files with 160 additions and 59 deletions
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65
src/coloredstderr.c
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@@ -78,6 +78,9 @@ static size_t (*real_fwrite)(void const *, size_t, size_t, FILE *);
static int initialized;
/* Force hooked writes even when not writing to a tty. Used for tests. */
static int force_write_to_non_tty;
/* Was ENV_NAME_FDS found and used when init_from_environment() was called?
* This is not true if the process set it manually after initialization. */
static int used_fds_set_by_user;
#include "constants.h"
@@ -508,34 +511,23 @@ pid_t vfork(void) {
/* Hook execve() and the other exec*() functions. Some shells use exec*() with
* a custom environment which doesn't necessarily contain our updates to
* ENV_NAME_FDS. It's also faster to update the environment only when
* necessary, right before the exec() to pass it to the new process. */
* ENV_NAME_PRIVATE_FDS. It's also faster to update the environment only when
* necessary, right before the exec(), to pass it to the new program. */
/* int execve(char const *, char * const [], char * const []) */
HOOK_FUNC_DEF3(int, execve, char const *, filename, char * const *, argv, char * const *, env) {
DLSYM_FUNCTION(real_execve, "execve");
int found = 0;
size_t index = 0;
/* Count arguments and search for existing ENV_NAME_FDS environment
* variable. */
/* Count environment variables. */
size_t count = 0;
char * const *x = env;
while (*x) {
if (!strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
found = 1;
index = count;
}
x++;
while (*x++) {
count++;
}
/* Terminating NULL. */
count++;
char *env_copy[count + 1 /* space for our new entry if necessary */];
memcpy(env_copy, env, count * sizeof(char *));
/* Make sure the information from the environment is loaded. We can't just
* do nothing (like update_environment()) because the caller might pass a
@@ -544,17 +536,40 @@ HOOK_FUNC_DEF3(int, execve, char const *, filename, char * const *, argv, char *
init_from_environment();
}
char fds_env[strlen(ENV_NAME_FDS) + 1 + update_environment_buffer_size()];
strcpy(fds_env, ENV_NAME_FDS "=");
update_environment_buffer(fds_env + strlen(ENV_NAME_FDS) + 1);
char fds_env[strlen(ENV_NAME_PRIVATE_FDS)
+ 1 + update_environment_buffer_size()];
strcpy(fds_env, ENV_NAME_PRIVATE_FDS "=");
update_environment_buffer(fds_env + strlen(ENV_NAME_PRIVATE_FDS) + 1);
if (found) {
env_copy[index] = fds_env;
} else {
/* If the process removed ENV_NAME_FDS from the environment, re-add
* it. */
env_copy[count-1] = fds_env;
env_copy[count] = NULL;
int found = 0;
char **x_copy = env_copy;
/* Copy the environment manually; allows skipping elements. */
x = env;
while ((*x_copy = *x)) {
/* Remove ENV_NAME_FDS if we've already used its value. The new
* program must use the updated list from ENV_NAME_PRIVATE_FDS. */
if (used_fds_set_by_user
&& !strncmp(*x, ENV_NAME_FDS "=", strlen(ENV_NAME_FDS) + 1)) {
x++;
continue;
/* Update ENV_NAME_PRIVATE_FDS. */
} else if (!strncmp(*x, ENV_NAME_PRIVATE_FDS "=",
strlen(ENV_NAME_PRIVATE_FDS) + 1)) {
*x_copy = fds_env;
found = 1;
}
x++;
x_copy++;
}
/* The loop "condition" NULL-terminates env_copy. */
if (!found) {
/* If the process removed ENV_NAME_PRIVATE_FDS from the environment,
* re-add it. */
*x_copy++ = fds_env;
*x_copy++ = NULL;
}
return real_execve(filename, argv, env_copy);