File syslog-locking.patch of Package glibc.18276
From 518db378cedc755f0ae311a1bc0487a4264f4bf0 Mon Sep 17 00:00:00 2001
From: Andreas Schwab <schwab@suse.de>
Date: Tue, 23 Jun 2020 12:55:49 +0200
Subject: [PATCH] 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.
---
misc/syslog.c | 44 ++++++++++++++++++++++++++++----------------
1 file changed, 28 insertions(+), 16 deletions(-)
Index: glibc-2.26/misc/syslog.c
===================================================================
--- glibc-2.26.orig/misc/syslog.c
+++ glibc-2.26/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);
}
@@ -155,9 +161,17 @@ __vsyslog_chk(int pri, int flag, const c
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)
@@ -224,6 +238,9 @@ __vsyslog_chk(int pri, int flag, const c
/* 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. */
@@ -241,22 +258,10 @@ __vsyslog_chk(int pri, int flag, const c
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));
@@ -309,6 +314,7 @@ __vsyslog_chk(int pri, int flag, const c
__sigaction (SIGPIPE, &oldaction, (struct sigaction *) NULL);
#endif
+ out:
/* End of critical section. */
__libc_cleanup_pop (0);
__libc_lock_unlock (syslog_lock);
@@ -429,8 +435,14 @@ 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);
}