From 42d359350510506b87101cf77202fefcbfc790cb Mon Sep 17 00:00:00 2001 From: Andreas Schwab Date: Thu, 27 May 2021 12:49:47 +0200 Subject: [PATCH 1/2] Use __pthread_attr_copy in mq_notify (bug 27896) Make a deep copy of the pthread attribute object to remove a potential use-after-free issue. CVE-2021-33574: The mq_notify function has a potential use-after-free issue when using a notification type of SIGEV_THREAD and a thread attribute with a non-default affinity mask. diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c index cc575a0cdd..f7ddfe5a6c 100644 --- a/sysdeps/unix/sysv/linux/mq_notify.c +++ b/sysdeps/unix/sysv/linux/mq_notify.c @@ -133,8 +133,11 @@ helper_thread (void *arg) (void) __pthread_barrier_wait (¬ify_barrier); } else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED) - /* The only state we keep is the copy of the thread attributes. */ - free (data.attr); + { + /* The only state we keep is the copy of the thread attributes. */ + pthread_attr_destroy (data.attr); + free (data.attr); + } } return NULL; } @@ -255,8 +258,7 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification) if (data.attr == NULL) return -1; - memcpy (data.attr, notification->sigev_notify_attributes, - sizeof (pthread_attr_t)); + __pthread_attr_copy (data.attr, notification->sigev_notify_attributes); } /* Construct the new request. */ @@ -270,7 +272,10 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification) /* If it failed, free the allocated memory. */ if (__glibc_unlikely (retval != 0)) - free (data.attr); + { + pthread_attr_destroy (data.attr); + free (data.attr); + } return retval; } -- 2.31.1 From 217b6dc298156bdb0d6aea9ea93e7e394a5ff091 Mon Sep 17 00:00:00 2001 From: Florian Weimer Date: Tue, 1 Jun 2021 17:51:41 +0200 Subject: [PATCH 2/2] Fix use of __pthread_attr_copy in mq_notify (bug 27896) __pthread_attr_copy can fail and does not initialize the attribute structure in that case. If __pthread_attr_copy is never called and there is no allocated attribute, pthread_attr_destroy should not be called, otherwise there is a null pointer dereference in rt/tst-mqueue6. Fixes commit 42d359350510506b87101cf77202fefcbfc790cb ("Use __pthread_attr_copy in mq_notify (bug 27896)"). Reviewed-by: Siddhesh Poyarekar --- sysdeps/unix/sysv/linux/mq_notify.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c index f7ddfe5a6c..6f46d29d1d 100644 --- a/sysdeps/unix/sysv/linux/mq_notify.c +++ b/sysdeps/unix/sysv/linux/mq_notify.c @@ -258,7 +258,14 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification) if (data.attr == NULL) return -1; - __pthread_attr_copy (data.attr, notification->sigev_notify_attributes); + int ret = __pthread_attr_copy (data.attr, + notification->sigev_notify_attributes); + if (ret != 0) + { + free (data.attr); + __set_errno (ret); + return -1; + } } /* Construct the new request. */ @@ -271,7 +278,7 @@ mq_notify (mqd_t mqdes, const struct sigevent *notification) int retval = INLINE_SYSCALL (mq_notify, 2, mqdes, &se); /* If it failed, free the allocated memory. */ - if (__glibc_unlikely (retval != 0)) + if (retval != 0 && data.attr != NULL) { pthread_attr_destroy (data.attr); free (data.attr); -- 2.31.1