Bug 987552 - (CVE-2016-6131) VUL-1: CVE-2016-6131: libiberty: Demangler segfaults (trackerbug)
(CVE-2016-6131)
VUL-1: CVE-2016-6131: libiberty: Demangler segfaults (trackerbug)
Status: RESOLVED MOVED
Classification: Novell Products
Product: SUSE Security Incidents
Classification: Novell Products
Component: Incidents
unspecified
Other Other
: P3 - Medium : Minor
: ---
Assigned To: Security Team bot
Security Team bot
https://smash.suse.de/issue/170574/
maint:planned:update
:
Depends on:
Blocks: 987631 987633 987637 987635 987644
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Reported: 2016-07-04 12:04 UTC by Andreas Stieger
Modified: 2019-12-10 09:53 UTC (History)
1 user (show)

See Also:
Found By: Security Response Team
Services Priority:
Business Priority:
Blocker: ---
Marketing QA Status: ---
IT Deployment: ---


Attachments
patch under review (5.50 KB, patch)
2016-07-04 12:04 UTC, Andreas Stieger
Details | Diff

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Description Andreas Stieger 2016-07-04 12:04:46 UTC
Created attachment 682931 [details]
patch under review

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71696

Another vulnerability in GNU Libiberty was found that impacts the security of binary analysis tools, such as Valgrind, 
GDB, Binutils (e.g., objdump, nm, ..), Gcov, or other LibBFD-based tools. An attacker might modify a program binary 
such that it executes malicious code upon *analysis* of the binary (e.g., to find whether it is malicious in the first 
place) or during the attempt to reverse-engineer an untrusted binary.

Workaround: Until the patches propagate to the vulnerable tools, switch off default demangling! E.g.,
$ echo "set demangle-style none"  >>  ~/.gdbinit
$ echo "--demangle=no" >> ~/.valgrindrc

A stackoverflow in the libiberty demangler causes its host application to crash on a tainted branch instruction. The 
problem is caused by a self-reference in a mangled type string that is "remembered" for later reference. This leads to 
an infinite recursion during the demangling.
* GDB exploitable classifies the stack overflow as exploitable.
* Bug Report: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71696
* Patch under review: https://gcc.gnu.org/ml/gcc-patches/2016-06/msg02030.html


From patch submission:


The attached patch fixes the stack overflow in the demangler due to cycles in the references of “remembered” mangled types (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71696).

The methods demangle_signature and do_arg in cplus-dem.c allow to “remember” mangled type names that can later be referenced and will also be demangled. The method demangle_args demangles those types following any references. So, if there is a cycle in the referencing (or in the simplest case a self-reference), the method enters infinite recursion.

The patch tracks the mangled types that are currently being demangled in a new variable called work->proctypevec. If a referenced type is currently being demangled, the demangling is marked as not successful.

Bootstrapped and regression tested on x86_64-pc-linux-gnu. Test case added to libiberty/testsuite/demangler-expected and checked PR71696 is resolved.





References:
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-6131
http://seclists.org/oss-sec/2016/q2/633
http://people.canonical.com/~ubuntu-security/cve/2016/CVE-2016-6131.html
Comment 3 Swamp Workflow Management 2016-07-04 22:00:40 UTC
bugbot adjusting priority
Comment 4 Andreas Stieger 2016-07-05 13:50:53 UTC
Security impact of this is marginal, not requesting update now.
Bugs tracking issues for packages embedding this lib:

bug 987631 binutils
bug 987633 crash
bug 987635 valgrind
bug 987637 gdb
bug 987644 gcc

Closing tracker.