Linux Kernel up to 4.19 sas_expander.c smp_task_timedout/smp_task_done race condition

Summaryinfo

A vulnerability labeled as critical has been found in Linux Kernel up to 4.19. Affected is the function smp_task_timedout/smp_task_done in the library drivers/scsi/libsas/sas_expander.c. Executing a manipulation can lead to race condition. This vulnerability is tracked as CVE-2018-20836. The attack can be launched remotely. No exploit exists. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical was found in Linux Kernel up to 4.19 (Operating System). This vulnerability affects the function smp_task_timedout/smp_task_done in the library drivers/scsi/libsas/sas_expander.c. The manipulation with an unknown input leads to a race condition vulnerability. The CWE definition for the vulnerability is CWE-362. The product contains a code sequence that can run concurrently with other code, and the code sequence requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence that is operating concurrently. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

An issue was discovered in the Linux kernel before 4.20. There is a race condition in smp_task_timedout() and smp_task_done() in drivers/scsi/libsas/sas_expander.c, leading to a use-after-free.

The weakness was disclosed 05/07/2019 (Website). The advisory is shared for download at access.redhat.com. This vulnerability was named CVE-2018-20836 since 05/07/2019. The attack can be initiated remotely. A single authentication is necessary for exploitation. There are known technical details, but no exploit is available.

The commercial vulnerability scanner Qualys is able to test this issue with plugin 157995 (Oracle Enterprise Linux Security Update for Unbreakable Enterprise kernel (ELSA-2019-4670)).

Upgrading to version 4.20 eliminates this vulnerability. The upgrade is hosted for download at git.kernel.org. The vulnerability will be addressed with the following lines of code:

del_timer(&task->slow_task->timer);

The vulnerability is also documented in the vulnerability database at SecurityFocus (BID 105388†). The entries VDB-124429, VDB-127125, VDB-134460 and VDB-134461 are pretty similar. Once again VulDB remains the best source for vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 4.0
• 4.1
• 4.2
• 4.3
• 4.4
• 4.5
• 4.6
• 4.7
• 4.8
• 4.9
• 4.10
• 4.11
• 4.12
• 4.13
• 4.14
• 4.15
• 4.16
• 4.17
• 4.18
• 4.19

License

• open-source

Website

• Vendor: https://www.kernel.org/

CPE 2.3info

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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