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tests/server: make the signal handler signal-safe

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Before this patch the signal handler called `logmsg()` which in turn
called `printf()` variants (internal implementations), and `FILE *`
functions, `localtime()`. Some of these called `malloc`/`free`, which
isn't supported in s signal handler. Replace them with `write` calls,
losing some logging functionality.

Also:
- De-dupe and move `STD*_FILENO` macros to `lib/curl_setup.h`. Revert
  the `src` definition to point to `stderr`, instead of `tool_stderr`.
  Follow-up to e5bb88b8f8 #11958

POSIX specs with list of functions allowed in a signal handler:
2004: https://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_04.html#tag_02_04_03
2017: https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html#tag_15_04_03
2024: https://pubs.opengroup.org/onlinepubs/9799919799/functions/V2_chap02.html#tag_16_04_03

Linux CI run with the thread sanitizer going crazy when
hitting the signal handler in test 1238 and 1242 (TFTP):
```
WARNING: ThreadSanitizer: signal-unsafe call inside of a signal (pid=12582)
    #0 malloc <null> (servers+0x5ed70)
    #1 _IO_file_doallocate <null> (libc.so.6+0x851b4)
    #2 formatf /home/runner/work/curl/curl/bld/tests/server/../../lib/../../lib/mprintf.c:886:9 (servers+0xdff77)
[...]
WARNING: ThreadSanitizer: signal-unsafe call inside of a signal (pid=12582)
    #0 free <null> (servers+0x5f453)
    #1 fclose <null> (libc.so.6+0x8532f)
    #2 logmsg /home/runner/work/curl/curl/bld/tests/server/../../../tests/server/util.c:134:5 (servers+0xe684d)
```
Ref: https://github.com/curl/curl/actions/runs/14118903372/job/39555309490?pr=16851

Closes #16852
This commit is contained in:
Viktor Szakats 2025-03-28 01:41:28 +01:00
parent 3b6c7142f6
commit e95f509c66
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GPG key ID: B5ABD165E2AEF201
5 changed files with 46 additions and 29 deletions
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11
tests/libtest/lib556.c
View file

@ -26,17 +26,6 @@
#include "warnless.h"
#include "memdebug.h"
/* For Windows, mainly (may be moved in a config file?) */
#ifndef STDIN_FILENO
#define STDIN_FILENO 0
#endif
#ifndef STDOUT_FILENO
#define STDOUT_FILENO 1
#endif
#ifndef STDERR_FILENO
#define STDERR_FILENO 2
#endif
CURLcode test(char *URL)
{
CURLcode res;

37
tests/server/util.c
View file

@ -445,10 +445,39 @@ HANDLE exit_event = NULL;
* store in exit_signal the signal that triggered its execution.
*/
#ifndef UNDER_CE
/*
* Only call signal-safe functions from the signal handler, as required by
* the POSIX specification:
* https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
* Hence, do not call 'logmsg()', and instead use 'open/write/close' to
* log errors.
*/
static void exit_signal_handler(int signum)
{
int old_errno = errno;
logmsg("exit_signal_handler (%d)", signum);
if(!serverlogfile) {
static const char msg[] = "exit_signal_handler: serverlogfile not set\n";
(void)!write(STDERR_FILENO, msg, sizeof(msg) - 1);
}
else {
#ifdef _WIN32
#define OPENMODE S_IREAD | S_IWRITE
#else
#define OPENMODE S_IRUSR | S_IWUSR
#endif
int fd = open(serverlogfile, O_WRONLY|O_CREAT|O_APPEND, OPENMODE);
if(fd != -1) {
static const char msg[] = "exit_signal_handler: called\n";
(void)!write(fd, msg, sizeof(msg) - 1);
close(fd);
}
else {
static const char msg[] = "exit_signal_handler: failed opening ";
(void)!write(STDERR_FILENO, msg, sizeof(msg) - 1);
(void)!write(STDERR_FILENO, serverlogfile, strlen(serverlogfile));
(void)!write(STDERR_FILENO, "\n", 1);
}
}
if(got_exit_signal == 0) {
got_exit_signal = 1;
exit_signal = signum;
@ -525,9 +554,9 @@ static LRESULT CALLBACK main_window_proc(HWND hwnd, UINT uMsg,
if(hwnd == hidden_main_window) {
switch(uMsg) {
#ifdef SIGTERM
case WM_CLOSE:
signum = SIGTERM;
break;
case WM_CLOSE:
signum = SIGTERM;
break;
#endif
case WM_DESTROY:
PostQuitMessage(0);