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Groups > linux.debian.kernel > #68922

Bug#977615: arm64: memory corruption bug

Cross-posted to 2 groups.

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Package: src:linux
Version: 4.19.160-2
Severity: important
Tags: upstream fixed-upstream
Control: fixed -1 5.9.15-1
Control: fixed -1 5.10~rc7-1~exp1
Control: found -1 5.9.11-1

Opening a bug for visibility.  Arguably this could be Severity: grave given
that memory corruption can lead to data loss.  It has been fixed upstream in
4.19.161, 5.9.12, and 5.10.  I'm not sure about the status for 4.9/stretch
LTS.

There is a memory corruption bug impacting arm64.  The upstream fix was made
in 5.10 with commit ff1712f953e2 ("arm64: pgtable: Ensure dirty bit is
preserved across pte_wrprotect()").  The upstream commit [1] describes the
issue as:

        With hardware dirty bit management, calling pte_wrprotect() on a
        writable, dirty PTE will lose the dirty state and return a
        read-only, clean entry.

Impact from the issue has been observed in the real world on systems running
redis, as described at https://github.com/redis/redis/issues/8124 (note in
particular comments [2] and [3], where the kernel connection is made).

1. https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ff1712f953e27f0b0718762ec17d0adb15c9fd0b
2. https://github.com/redis/redis/issues/8124#issuecomment-745791340
3. https://github.com/redis/redis/issues/8124#issuecomment-745838911

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Bug#977615: arm64: memory corruption bug Noah Meyerhans <noahm@debian.org> - 2020-12-17 21:20 +0100
  Bug#977615: arm64: memory corruption bug Salvatore Bonaccorso <carnil@debian.org> - 2020-12-17 21:30 +0100
    Bug#977615: arm64: memory corruption bug Noah Meyerhans <noahm@debian.org> - 2020-12-17 23:00 +0100

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