Bug 2420309 (CVE-2023-53832)

Summary: CVE-2023-53832 kernel: md/raid10: fix null-ptr-deref in raid10_sync_request
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A null pointer dereference flaw was found in the Linux kernel's RAID10 implementation. When recovery is skipped on a clean array, init_resync() is called but close_sync() is not, leaving conf->have_replacement incorrectly set to 0. If a replacement device is later added and recovery is triggered, repl_bio is not allocated, causing a null pointer dereference when accessed.
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Description OSIDB Bzimport 2025-12-09 02:01:53 UTC
In the Linux kernel, the following vulnerability has been resolved:

md/raid10: fix null-ptr-deref in raid10_sync_request

init_resync() inits mempool and sets conf->have_replacemnt at the beginning
of sync, close_sync() frees the mempool when sync is completed.

After [1] recovery might be skipped and init_resync() is called but
close_sync() is not. null-ptr-deref occurs with r10bio->dev[i].repl_bio.

The following is one way to reproduce the issue.

  1) create a array, wait for resync to complete, mddev->recovery_cp is set
     to MaxSector.
  2) recovery is woken and it is skipped. conf->have_replacement is set to
     0 in init_resync(). close_sync() not called.
  3) some io errors and rdev A is set to WantReplacement.
  4) a new device is added and set to A's replacement.
  5) recovery is woken, A have replacement, but conf->have_replacemnt is
     0. r10bio->dev[i].repl_bio will not be alloced and null-ptr-deref
     occurs.

Fix it by not calling init_resync() if recovery skipped.

[1] commit 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean arrays are assembled")