CVE-2026-46089
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zram Partial Discard Request Endio Missing

Publication date: 2026-05-27

Last updated on: 2026-05-27

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: zram: do not forget to endio for partial discard requests As reported by Qu Wenruo and Avinesh Kumar, the following getconf PAGESIZE 65536 blkdiscard -p 4k /dev/zram0 takes literally forever to complete. zram doesn't support partial discards and just returns immediately w/o doing any discard work in such cases. The problem is that we forget to endio on our way out, so blkdiscard sleeps forever in submit_bio_wait(). Fix this by jumping to end_bio label, which does bio_endio().
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Meta Information
Published
2026-05-27
Last Modified
2026-05-27
Generated
2026-06-16
AI Q&A
2026-05-27
EPSS Evaluated
2026-06-15
NVD
CVE-2026-46089
EUVD
EUVD-2026-32472
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
linux_kernel zram *
linux linux_kernel *
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-UNKNOWN
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Impact Analysis

The impact of this vulnerability is that certain discard operations on zram devices can hang indefinitely. For example, running blkdiscard with partial discard requests may cause the command to never complete, potentially leading to system hangs or delays in storage management tasks that rely on discard operations.

Executive Summary

This vulnerability exists in the Linux kernel's zram component. When a partial discard request is made, zram does not support it and returns immediately without performing any discard operation. However, it fails to properly signal the completion of the I/O operation (endio), causing commands like blkdiscard to hang indefinitely while waiting for the operation to complete.

Detection Guidance

This vulnerability can be detected by observing the behavior of the blkdiscard command on zram devices. Specifically, running a partial discard request on a zram device may cause the command to hang indefinitely.

  • Run the command: getconf PAGESIZE to determine the system page size.
  • Run the command: blkdiscard -p 4k /dev/zram0 and observe if it takes an unusually long time or hangs.

If blkdiscard hangs or takes forever to complete on partial discard requests, it indicates the presence of this vulnerability.

Mitigation Strategies

The vulnerability is fixed by ensuring that the endio operation is properly called for partial discard requests in the zram driver. Immediate mitigation steps include:

  • Update the Linux kernel to a version that includes the fix for this vulnerability.
  • Avoid running partial discard requests on zram devices until the fix is applied.

Since the issue causes blkdiscard to hang indefinitely, avoiding such operations or applying the kernel patch will mitigate the problem.

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