tunables: Terminate if end of input is reached (CVE-2023-4911)

The string parsing routine may end up writing beyond bounds of tunestr
if the input tunable string is malformed, of the form name=name=val.
This gets processed twice, first as name=name=val and next as name=val,
resulting in tunestr being name=name=val:name=val, thus overflowing
tunestr.

Terminate the parsing loop at the first instance itself so that tunestr
does not overflow.

This also fixes up tst-env-setuid-tunables to actually handle failures
correct and add new tests to validate the fix for this CVE.

Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>
(cherry picked from commit 1056e5b4c3f2d90ed2b4a55f96add28da2f4c8fa)

1 files changed, 5 insertions, 0 deletions

diff --git a/NEWS b/NEWS
index 3725cc4820..b351537a78 100644
--- a/NEWS
+++ b/NEWS
@@ -31,6 +31,11 @@ Security related changes:
   an application calls getaddrinfo for AF_INET6 with AI_CANONNAME,
   AI_ALL and AI_V4MAPPED flags set.
 
+  CVE-2023-4911: If a tunable of the form NAME=NAME=VAL is passed in the
+  environment of a setuid program and NAME is valid, it may result in a
+  buffer overflow, which could be exploited to achieve escalated
+  privileges.  This flaw was introduced in glibc 2.34.
+
 The following bugs are resolved with this release:
 
   [20975] Deferred cancellation triggers in __check_pf and looses lock leading to deadlock