Andrew Geissler | d159c7f | 2021-09-02 21:05:58 -0500 | [diff] [blame] | 1 | From b805aebd42364fe696e417808a700fdb9800c9e8 Mon Sep 17 00:00:00 2001 |
| 2 | From: Nikita Popov <npv1310@gmail.com> |
| 3 | Date: Mon, 9 Aug 2021 20:17:34 +0530 |
| 4 | Subject: [PATCH] librt: fix NULL pointer dereference (bug 28213) |
| 5 | |
| 6 | Helper thread frees copied attribute on NOTIFY_REMOVED message |
| 7 | received from the OS kernel. Unfortunately, it fails to check whether |
| 8 | copied attribute actually exists (data.attr != NULL). This worked |
| 9 | earlier because free() checks passed pointer before actually |
| 10 | attempting to release corresponding memory. But |
| 11 | __pthread_attr_destroy assumes pointer is not NULL. |
| 12 | |
| 13 | So passing NULL pointer to __pthread_attr_destroy will result in |
| 14 | segmentation fault. This scenario is possible if |
| 15 | notification->sigev_notify_attributes == NULL (which means default |
| 16 | thread attributes should be used). |
| 17 | |
| 18 | Upstream-Status: Backport [https://sourceware.org/git/?p=glibc.git;a=commit;h=b805aebd42364fe696e417808a700fdb9800c9e8] |
| 19 | CVE: CVE-2021-38604 |
| 20 | |
| 21 | Signed-off-by: Nikita Popov <npv1310@gmail.com> |
| 22 | Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org> |
| 23 | Signed-off-by: Vinay Kumar <vinay.m.engg@gmail.com> |
| 24 | --- |
| 25 | sysdeps/unix/sysv/linux/mq_notify.c | 2 +- |
| 26 | 1 file changed, 1 insertion(+), 1 deletion(-) |
| 27 | |
| 28 | diff --git a/sysdeps/unix/sysv/linux/mq_notify.c b/sysdeps/unix/sysv/linux/mq_notify.c |
| 29 | index 9799dcdaa4..eccae2e4c6 100644 |
| 30 | --- a/sysdeps/unix/sysv/linux/mq_notify.c |
| 31 | +++ b/sysdeps/unix/sysv/linux/mq_notify.c |
| 32 | @@ -131,7 +131,7 @@ helper_thread (void *arg) |
| 33 | to wait until it is done with it. */ |
| 34 | (void) __pthread_barrier_wait (¬ify_barrier); |
| 35 | } |
| 36 | - else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED) |
| 37 | + else if (data.raw[NOTIFY_COOKIE_LEN - 1] == NOTIFY_REMOVED && data.attr != NULL) |
| 38 | { |
| 39 | /* The only state we keep is the copy of the thread attributes. */ |
| 40 | __pthread_attr_destroy (data.attr); |
| 41 | -- |
| 42 | 2.31.1 |
| 43 | |