Bug 1902724 (CVE-2020-35508)
| Summary: | CVE-2020-35508 kernel: fork: fix copy_process(CLONE_PARENT) race with the exiting ->real_parent | ||
|---|---|---|---|
| Product: | [Other] Security Response | Reporter: | Guilherme de Almeida Suckevicz <gsuckevi> |
| Component: | vulnerability | Assignee: | Red Hat Product Security <security-response-team> |
| Status: | CLOSED ERRATA | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | unspecified | CC: | acaringi, adscvr, airlied, allarkin, aquini, bhu, blc, bmasney, brdeoliv, bskeggs, chwhite, dhoward, dvlasenk, esammons, eshatokhin, fhrbata, hdegoede, hkrzesin, iboverma, itamar, jarodwilson, jeremy, jforbes, jglisse, jlelli, jonathan, josef, jross, jshortt, jstancek, jwboyer, kcarcia, kernel-maint, kernel-mgr, lgoncalv, linville, masami256, mchehab, mcressma, michael.hebenstreit, mlangsdo, mmilgram, nmurray, pmatouse, ptalbert, qzhao, rt-maint, rvrbovsk, security-response-team, steved, walters, williams |
| Target Milestone: | --- | Keywords: | Security |
| Target Release: | --- | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |
| Doc Text: |
A flaw possibility of race condition and incorrect initialization of the process id was found in the Linux kernel child/parent process identification handling while filtering signal handlers. A local attacker is able to abuse this flaw to bypass checks to send any signal to a privileged process.
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Story Points: | --- |
| Clone Of: | Environment: | ||
| Last Closed: | 2021-05-18 20:37:35 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: | 1895892, 1904784, 1904785, 1908311, 1950760, 1962333, 1962334 | ||
| Bug Blocks: | 1896156, 1939994 | ||
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Description
Guilherme de Almeida Suckevicz
2020-11-30 14:01:40 UTC
Mitigation: Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. The "incorrect initialization of the process id" of the flaw is actual only for Red Hat Enterprise Linux (starting from 8.3), and non-actual for other (upstream) Linux distributions.
More details about this:
In fork.c:dup_task_struct(), after task->task_struct_rh allocated by kmalloc_node(), task_struct_rh->self_exec_id and
task_struct_rh->vtime_cpu are not initialized, which upstream do initialize them in arch_dup_task_struct().
Steps to Reproduce:
1. Compile this module
int init_module(void)
{
printk(KERN_INFO "[parent ] parent_exec_id: %llu, self_exec_id: %llu\n",
current->real_parent->task_struct_rh->parent_exec_id, current->real_parent->task_struct_rh->self_exec_id);
printk(KERN_INFO "[current] parent_exec_id: %llu, self_exec_id: %llu\n",
current->task_struct_rh->parent_exec_id, current->task_struct_rh->self_exec_id);
return 0;
}
2. Load it and check dmesg output
Actual results:
[264937.255323] [parent ] parent_exec_id: 64, self_exec_id: 481036337297 <-- seems it is some random value from slab
[264937.255324] [current] parent_exec_id: 481036337297, self_exec_id: 481036337297
Expected results:
[264937.255323] [parent ] parent_exec_id: 64, self_exec_id: 65
[264937.255324] [current] parent_exec_id: 65, self_exec_id: 65
Additional information about the possibility of the integer overflow for the value tsk->parent->self_exec_id: https://lore.kernel.org/kernel-hardening/20200324215049.GA3710@pi3.com.pl/ Statement: The incorrect initialization of the process id affects Red Hat Enterprise Linux only. The description of the flaw: "A flaw possibility of race condition and incorrect initialization of the process id was found in the Linux kernel child/parent process identification handling while filtering signal handlers. A local attacker is able to abuse this flaw to bypass checks to send any signal to a privileged process." The patch from the reference is for the "race condition" only: https://github.com/torvalds/linux/commit/b4e00444cab4c3f3fec876dc0cccc8cbb0d1a948 The other patch for the "incorrect initialization of the process id" is internal and for the Red Hat Enterprise Linux only: https://mailman-eng.corp.redhat.com/archives/rhkernel-list/2020-December/498644.html Acknowledgments: Name: Eddy Wu (trendmicro.com) This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:1578 https://access.redhat.com/errata/RHSA-2021:1578 This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2021:1739 https://access.redhat.com/errata/RHSA-2021:1739 This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2020-35508 the code changes from https://github.com/torvalds/linux/commit/b4e00444cab4c3f3fec876dc0cccc8cbb0d1a948 are not in the RH8.4 kernel just released could you attach the info from https://mailman-eng.corp.redhat.com/archives/rhkernel-list/2020-December/498644.html here as that address is RedHat internal? This issue has been addressed in the following products: Red Hat Enterprise Linux 8.2 Extended Update Support Via RHSA-2021:2719 https://access.redhat.com/errata/RHSA-2021:2719 This issue has been addressed in the following products: Red Hat Enterprise Linux 8.2 Extended Update Support Via RHSA-2021:2718 https://access.redhat.com/errata/RHSA-2021:2718 |