Bug 1334307 (CVE-2016-4557)

Summary: CVE-2016-4557 kernel: Use after free vulnerability via double fdput
Product: [Other] Security Response Reporter: Adam Mariš <amaris>
Component: vulnerabilityAssignee: Red Hat Product Security <security-response-team>
Status: CLOSED ERRATA QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: agordeev, aquini, arm-mgr, bhu, dhoward, esammons, fhrbata, gansalmon, iboverma, itamar, jforbes, jkacur, joelsmith, jonathan, jross, jwboyer, kernel-maint, kernel-mgr, kstutsma, lgoncalv, lwang, madhu.chinakonda, matt, mchehab, mcressma, mguzik, nmurray, plougher, rt-maint, rvrbovsk, slawomir, williams, wmealing
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: Bug Fix
Doc Text:
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Clone Of: Environment:
Last Closed: 2018-02-05 07:13:20 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 1334311, 1346578    
Bug Blocks: 1334304    

Description Adam Mariš 2016-05-09 11:20:45 UTC 
A use after free vulnerability was found in kernel which allows privilege escalation for users with a local account on the system. When a program was loaded with a bpf program an attacker could exploit this to gain root privileges by an unprivileged user.


When bpf(BPF_PROG_LOAD, ...) was invoked with a BPF program whose bytecode references a non-map file descriptor as a map file descriptor, the error handling code called fdput() twice instead of once (in __bpf_map_get() and in replace_map_fd_with_map_ptr()). If the file descriptor table of the current task is shared, this causes f_count to be decremented too much, allowing the struct file to be freed while it is still in use (use-after-free).

Bug was introduced in 0246e64d9a5f and is exploitable since 1be7f75d1668 without the need for CAP_SYS_ADMIN capability.

Upstream patch:

https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=8358b02bf67d3a5d8a825070e1aa73f25fb2e4c7

Original report:

https://bugs.chromium.org/p/project-zero/issues/detail?id=808

CVE request:

http://seclists.org/oss-sec/2016/q2/263
Comment 1 Adam Mariš 2016-05-09 11:28:48 UTC 
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1334311]
Comment 2 Wade Mealing 2016-05-11 01:38:48 UTC 
Statement:

This issue does not affect the Linux kernels as shipped with Red Hat Enterprise Linux 5, 6, 7 and Red Hat Enterprise MRG 2.
Comment 5 Fedora Update System 2016-05-14 23:22:33 UTC 
kernel-4.5.4-300.fc24 has been pushed to the Fedora 24 stable repository. If problems still persist, please make note of it in this bug report.
Comment 6 Fedora Update System 2016-05-25 00:53:19 UTC 
kernel-4.4.10-200.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Comment 7 Fedora Update System 2016-06-02 14:59:22 UTC 
kernel-4.5.5-201.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.