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CVE PROGRAM SOURCE RECORDUnscored

CVE-2021-46990

powerpc/64s: Fix crashes when toggling entry flush barrier

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Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: powerpc/64s: Fix crashes when toggling entry flush barrier The entry flush mitigation can be enabled/disabled at runtime via a debugfs file (entry_flush), which causes the kernel to patch itself to enable/disable the relevant mitigations. However depending on which mitigation we're using, it may not be safe to do that patching while other CPUs are active. For example the following crash: sleeper[15639]: segfault (11) at c000000000004c20 nip c000000000004c20 lr c000000000004c20 Shows that we returned to userspace with a corrupted LR that points into the kernel, due to executing the partially patched call to the fallback entry flush (ie. we missed the LR restore). Fix it by doing the patching under stop machine. The CPUs that aren't doing the patching will be spinning in the core of the stop machine logic. That is currently sufficient for our purposes, because none of the patching we do is to that code or anywhere in the vicinity.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • 4a1e90af718d1489ffcecc8f52486c4f5dc0f7a6 to < 8382b15864e5014261b4f36c2aa89723612ee058affected
  • fa4bf9f38184ed7ca4916eb64f8c767d1e279c1f to < 0c25a7bb697f2e6ee65b6d63782f675bf129511aaffected
  • db01cad9efe3c3838a6b3a3f68affd295c4b92d6 to < ee4b7aab93c2631c3bb0753023c5dda592bb666baffected
  • f69bb4e51f41973fb7594be1479fa689831efe1a to < 2db22ba4e0e103f00e0512e0ecce36ac78c644f8affected
  • b65458b6be8032c5179d4f562038575d7b3a6be3 to < 0b4eb172cc12dc102cd0ad013e53ee4463db9508affected
  • f79643787e0a0762d2409b7b8334e83f22d85695 to < d2e3590ca39ccfd8a5a46d8c7f095cb6c7b9ae92affected
  • f79643787e0a0762d2409b7b8334e83f22d85695 to < dd0d6117052faace5440db20fc37175efe921c7daffected
  • f79643787e0a0762d2409b7b8334e83f22d85695 to < 5bc00fdda1e934c557351a9c751a205293e68cbfaffected
  • f79643787e0a0762d2409b7b8334e83f22d85695 to < aec86b052df6541cc97c5fca44e5934cbea4963baffected
  • e590b36718d6e740b7b19514f710402a6499164caffected
  • 4.4.245 to < 4.4.269affected
  • 4.9.245 to < 4.9.269affected
  • 4.14.208 to < 4.14.233affected
  • 4.19.159 to < 4.19.191affected
  • 5.4.79 to < 5.4.120affected
  • 5.9.10 to < 5.10affected

Linux Linux

Default version status: affected

  • 5.10affected
  • 0 to < 5.10unaffected
  • 4.4.269 to ≤ 4.4.*unaffected
  • 4.9.269 to ≤ 4.9.*unaffected
  • 4.14.233 to ≤ 4.14.*unaffected
  • 4.19.191 to ≤ 4.19.*unaffected
  • 5.4.120 to ≤ 5.4.*unaffected
  • 5.10.38 to ≤ 5.10.*unaffected
  • 5.11.22 to ≤ 5.11.*unaffected
  • 5.12.5 to ≤ 5.12.*unaffected
  • 5.13 to ≤ *unaffected

References