Bug 1268270 - (CVE-2015-7613) CVE-2015-7613 kernel: Unauthorized access to IPC objects with SysV shm
CVE-2015-7613 kernel: Unauthorized access to IPC objects with SysV shm
Status: CLOSED ERRATA
Product: Security Response
Classification: Other
Component: vulnerability (Show other bugs)
unspecified
All Linux
high Severity high
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Assigned To: Red Hat Product Security
impact=important,public=20151001,repo...
: Security
Depends On: 1271510 1268273 1271502 1271504 1271505 1271506 1271507 1271508 1271509
Blocks: 1268271
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Reported: 2015-10-02 07:50 EDT by Adam Mariš
Modified: 2016-05-20 03:21 EDT (History)
43 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
A race condition flaw was found in the way the Linux kernel's IPC subsystem initialized certain fields in an IPC object structure that were later used for permission checking before inserting the object into a globally visible list. A local, unprivileged user could potentially use this flaw to elevate their privileges on the system.
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Clone Of:
Environment:
Last Closed: 2016-05-20 03:21:43 EDT
Type: ---
Regression: ---
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CRM:
Verified Versions:
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---


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Description Adam Mariš 2015-10-02 07:50:35 EDT
A data race that can trick the kernel into using initialized memory was found. This vulnerability can at least give access to arbitrary SysV shared memory. It is almost certain that this vulnerability can be used to gain arbitrary code execution in the kernel.

While working on KTSAN, Dmitry Vyukov got a report that says that ipc_addid() installs a not-completely initialized object into the shared object table. In particular, uid/gid are not initialized. ipc_obtain_object_check() in turn obtains the object and verifies uid/gid for permission purposes. Since the fields are not initialized, the check can falsely succeed.

Race report:

ThreadSanitizer: data-race in ipc_obtain_object_check

Read at 0xffff88047f810f68 of size 8 by thread 2749 on CPU 5:
 [<ffffffff8147d84d>] ipc_obtain_object_check+0x7d/0xd0 ipc/util.c:621
 [<     inline     >] msq_obtain_object_check ipc/msg.c:90
 [<ffffffff8147e708>] msgctl_nolock.constprop.9+0x208/0x430 ipc/msg.c:480
 [<     inline     >] SYSC_msgctl ipc/msg.c:538
 [<ffffffff8147f061>] SyS_msgctl+0xa1/0xb0 ipc/msg.c:522
 [<ffffffff81ee3e11>] entry_SYSCALL_64_fastpath+0x31/0x95
arch/x86/entry/entry_64.S:188

Previous write at 0xffff88047f810f68 of size 8 by thread 2755 on CPU 4:
 [<ffffffff8147cf97>] ipc_addid+0x217/0x260 ipc/util.c:257
 [<ffffffff8147eb4c>] newque+0xac/0x240 ipc/msg.c:141
 [<     inline     >] ipcget_public ipc/util.c:355
 [<ffffffff8147daa2>] ipcget+0x202/0x280 ipc/util.c:646
 [<     inline     >] SYSC_msgget ipc/msg.c:255
 [<ffffffff8147efaa>] SyS_msgget+0x7a/0x90 ipc/msg.c:241
 [<ffffffff81ee3e11>] entry_SYSCALL_64_fastpath+0x31/0x95
arch/x86/entry/entry_64.S:188

Mutexes locked by thread 2755:
Mutex 445417 is locked here:
 [<ffffffff81ee0d45>] down_write+0x65/0x80 kernel/locking/rwsem.c:62
 [<     inline     >] ipcget_public ipc/util.c:348
 [<ffffffff8147d90c>] ipcget+0x6c/0x280 ipc/util.c:646
 [<     inline     >] SYSC_msgget ipc/msg.c:255
 [<ffffffff8147efaa>] SyS_msgget+0x7a/0x90 ipc/msg.c:241
 [<ffffffff81ee3e11>] entry_SYSCALL_64_fastpath+0x31/0x95
arch/x86/entry/entry_64.S:188

Mutex 453634 is locked here:
 [<     inline     >] __raw_spin_lock include/linux/spinlock_api_smp.h:158
 [<ffffffff81ee37d0>] _raw_spin_lock+0x50/0x70 kernel/locking/spinlock.c:151
 [<     inline     >] spin_lock include/linux/spinlock.h:312
 [<ffffffff8147ce0e>] ipc_addid+0x8e/0x260 ipc/util.c:238
 [<ffffffff8147eb4c>] newque+0xac/0x240 ipc/msg.c:141
 [<     inline     >] ipcget_public ipc/util.c:355
 [<ffffffff8147daa2>] ipcget+0x202/0x280 ipc/util.c:646
 [<     inline     >] SYSC_msgget ipc/msg.c:255
 [<ffffffff8147efaa>] SyS_msgget+0x7a/0x90 ipc/msg.c:241
 [<ffffffff81ee3e11>] entry_SYSCALL_64_fastpath+0x31/0x95
arch/x86/entry/entry_64.S:188

ipc_addid installs new ipc object with idr_alloc, from this point on
it is accessible to other threads. At this point the object contains
unitialized garbage. Then it fills in uid, etc:

new->cuid = new->uid = euid;
new->gid = new->cgid = egid;
new->seq = ids->seq++;

While this happens another thread can get access to the object and do
uid check on the unitialized garbage, which can give falsely give
accesses to the shared object to a process that should not have access
to the object.

Upstream patch:

https://github.com/torvalds/linux/commit/b9a532277938

CVE assignment: 

http://seclists.org/oss-sec/2015/q4/7
Comment 1 Adam Mariš 2015-10-02 07:53:23 EDT
Created kernel tracking bugs for this issue:

Affects: fedora-all [bug 1268273]
Comment 2 Fedora Update System 2015-10-09 02:15:37 EDT
kernel-4.2.3-300.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.
Comment 3 Fedora Update System 2015-10-09 06:27:03 EDT
kernel-4.1.10-200.fc22 has been pushed to the Fedora 22 stable repository. If problems still persist, please make note of it in this bug report.
Comment 6 Wade Mealing 2015-10-21 01:56:32 EDT
Statement:

This issue does not affect the Linux kernels as shipped with Red Hat Enterprise Linux 5.

This issue affects the Linux kernels as shipped with Red Hat Enterprise Linux 6, 7 and Red Hat MRG 2 kernels. Future kernel updates for the respective releases may address this issue.
Comment 9 Fedora Update System 2015-11-01 17:21:03 EST
kernel-4.1.10-100.fc21 has been pushed to the Fedora 21 stable repository. If problems still persist, please make note of it in this bug report.
Comment 14 errata-xmlrpc 2015-11-19 08:21:45 EST
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2411 https://rhn.redhat.com/errata/RHSA-2015-2411.html
Comment 15 errata-xmlrpc 2015-11-19 18:21:40 EST
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7

Via RHSA-2015:2152 https://rhn.redhat.com/errata/RHSA-2015-2152.html
Comment 17 errata-xmlrpc 2015-12-09 04:47:42 EST
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 7.1 EUS - Server and Compute Node Only
  Red Hat Enterprise Linux 7.1 EUS  - Server and Compute Node Only

Via RHSA-2015:2587 https://rhn.redhat.com/errata/RHSA-2015-2587.html
Comment 18 errata-xmlrpc 2015-12-15 08:58:44 EST
This issue has been addressed in the following products:

  Red Hat Enterprise Linux 6

Via RHSA-2015:2636 https://rhn.redhat.com/errata/RHSA-2015-2636.html

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