From: Andreas Schwab Date: Tue, 23 Jun 2020 10:55:49 +0000 (+0200) Subject: Correct locking and cancellation cleanup in syslog functions (bug 26100) X-Git-Tag: glibc-2.33~565 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c4e4b2e149705559d28b16a9b47ba2f6142d6a6c;p=thirdparty%2Fglibc.git Correct locking and cancellation cleanup in syslog functions (bug 26100) Properly serialize the access to the global state shared between the syslog functions, to avoid races in multithreaded processes. Protect a local allocation in the __vsyslog_internal function from leaking during cancellation. --- diff --git a/misc/syslog.c b/misc/syslog.c index fd6537edf60..2cc63ef287a 100644 --- a/misc/syslog.c +++ b/misc/syslog.c @@ -91,14 +91,20 @@ struct cleanup_arg static void cancel_handler (void *ptr) { -#ifndef NO_SIGPIPE /* Restore the old signal handler. */ struct cleanup_arg *clarg = (struct cleanup_arg *) ptr; - if (clarg != NULL && clarg->oldaction != NULL) - __sigaction (SIGPIPE, clarg->oldaction, NULL); + if (clarg != NULL) + { +#ifndef NO_SIGPIPE + if (clarg->oldaction != NULL) + __sigaction (SIGPIPE, clarg->oldaction, NULL); #endif + /* Free the memstream buffer, */ + free (clarg->buf); + } + /* Free the lock. */ __libc_lock_unlock (syslog_lock); } @@ -169,9 +175,17 @@ __vsyslog_internal(int pri, const char *fmt, va_list ap, pri &= LOG_PRIMASK|LOG_FACMASK; } + /* Prepare for multiple users. We have to take care: most + syscalls we are using are cancellation points. */ + struct cleanup_arg clarg; + clarg.buf = NULL; + clarg.oldaction = NULL; + __libc_cleanup_push (cancel_handler, &clarg); + __libc_lock_lock (syslog_lock); + /* Check priority against setlogmask values. */ if ((LOG_MASK (LOG_PRI (pri)) & LogMask) == 0) - return; + goto out; /* Set default facility if none specified. */ if ((pri & LOG_FACMASK) == 0) @@ -235,6 +249,9 @@ __vsyslog_internal(int pri, const char *fmt, va_list ap, /* Close the memory stream; this will finalize the data into a malloc'd buffer in BUF. */ fclose (f); + + /* Tell the cancellation handler to free this buffer. */ + clarg.buf = buf; } /* Output to stderr if requested. */ @@ -252,22 +269,10 @@ __vsyslog_internal(int pri, const char *fmt, va_list ap, v->iov_len = 1; } - __libc_cleanup_push (free, buf == failbuf ? NULL : buf); - /* writev is a cancellation point. */ (void)__writev(STDERR_FILENO, iov, v - iov + 1); - - __libc_cleanup_pop (0); } - /* Prepare for multiple users. We have to take care: open and - write are cancellation points. */ - struct cleanup_arg clarg; - clarg.buf = buf; - clarg.oldaction = NULL; - __libc_cleanup_push (cancel_handler, &clarg); - __libc_lock_lock (syslog_lock); - #ifndef NO_SIGPIPE /* Prepare for a broken connection. */ memset (&action, 0, sizeof (action)); @@ -320,6 +325,7 @@ __vsyslog_internal(int pri, const char *fmt, va_list ap, __sigaction (SIGPIPE, &oldaction, (struct sigaction *) NULL); #endif + out: /* End of critical section. */ __libc_cleanup_pop (0); __libc_lock_unlock (syslog_lock); @@ -430,8 +436,14 @@ setlogmask (int pmask) { int omask; + /* Protect against multiple users. */ + __libc_lock_lock (syslog_lock); + omask = LogMask; if (pmask != 0) LogMask = pmask; + + __libc_lock_unlock (syslog_lock); + return (omask); }