Re-apply SA_ONSTACK to every extension signal handler, not only SIGSEGV/SIGBUS/SIGFPE
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- 25/100
- Issue 类型
- 缺陷
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- 基本清楚
- 活跃度
- 停滞
调研方向
Start at frankenphp_startup() and inspect the signal-handler setup added after php_module_startup(), along with the existing handling for SIGSEGV, SIGBUS and SIGFPE. Check how signal flags are read and reapplied, then run the reproduction with dd-trace-php under HTTP load while sending SIGVTALRM. Done means extension handlers receive SA_ONSTACK and the reproduction no longer crashes; pull request #2746 is already open for this issue.
由索引模型根据 Issue 内容生成。
描述
What happened?
frankenphp_startup() adds SA_ONSTACK to extension-installed handlers after php_module_startup(), but only for SIGSEGV, SIGBUS and SIGFPE (#2650). Asynchronous signals have the same problem, with a quieter failure. When such a handler runs on a Go thread, it runs on the interrupted goroutine's stack, and the kernel's signal frame overflows into the neighbouring goroutine's stack. Nothing fails at delivery; the process dies later in GC with traceback did not unwind completely, unknown caller pc, fatal error: fault or SIGSEGV.
A real case is dd-trace-php (DataDog/dd-trace-php#4354). It installs SIGINT/SIGTERM handlers (fixed in 1.26.1) and a SIGVTALRM handler (still unfixed) without SA_ONSTACK, and its sidecar kill()s the process with SIGVTALRM on every remote-config change. In production this crashed FrankenPHP 1.12.7 and 1.13.2 in classic mode roughly once a day per service, on x86_64.
To reproduce: FrankenPHP 1.13.2 Docker image with dd-trace-php 1.25.1, a trivial PHP script under HTTP load, and kill -VTALRM <frankenphp pid> in a loop. The process dies with exit code 2 within about a second (5/5 runs). With SA_ONSTACK re-applied to every handler after module startup, it survives 90 s and about 3M signals (3/3 runs).
Would you take a change that loops over every signal instead of the three fault signals?
for (int sig = 1; sig < NSIG; sig++) {
struct sigaction sa;
if (sigaction(sig, NULL, &sa) == 0 && sa.sa_handler != SIG_DFL &&
sa.sa_handler != SIG_IGN && !(sa.sa_flags & SA_ONSTACK)) {
sa.sa_flags |= SA_ONSTACK;
sigaction(sig, &sa, NULL);
}
}
Go's own handlers already carry the flag, so only extension handlers would change. Handlers installed after startup, such as pcntl_signal(), stay out of reach, as they are today.
Build Type
Docker (Debian Trixie)
Worker Mode
No
Operating System
GNU/Linux
CPU Architecture
aarch64
PHP configuration
phpinfo() output
PHP 8.5.12 (ZTS), FrankenPHP v1.13.2 (Go 1.27.3), dunglas/frankenphp:1.13.2-php8.5.12
dd-trace-php 1.25.1: datadog-setup.php --php-bin=all --enable-appsec --enable-profiling
Extensions: Core ctype curl datadog-profiling date ddappsec ddtrace dom fileinfo filter hash iconv intl json lexbor libxml mbstring mysqlnd openssl pcntl pcre PDO pdo_sqlite Phar posix random readline redis Reflection session SimpleXML sockets sodium SPL sqlite3 standard tokenizer uri xml xmlreader xmlwriter Zend OPcache zip zlib
Relevant log output
Relevant log output
runtime: g33: frame.sp=0x3c1e0fa67610 top=0x3c1e0fa677d0
fatal error: traceback did not unwind completely
unexpected fault address 0xb5e216432b0fbb01
fatal error: fault
[signal SIGSEGV: segmentation violation code=0x1 addr=0xb5e216432b0fbb01 pc=0x45ab10]
runtime: g 857: unexpected return pc for runtime.netpollblock called from 0x5550000055550000
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