[Bug 2032577] Re: xz crashed with SIGSEGV in lzma_lzma_optimum_normal

[Thorsten Glaser]

That sounds even more like a RAM issue (that it stopped occurring with
the same kernel and software version).

Perhaps when you switched away from Wayland, your graphics card is now
used less heavily, and when the GPU was used more, the RAM got hotter or
got minimally less power and therefore had issues, or something. (This
is something people have indeed seen, so…)

If you can trigger it reliably again, the changes would indeed be
interesting.

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Title:
  xz crashed with SIGSEGV in lzma_lzma_optimum_normal

Status in xz-utils package in Ubuntu:
  New

Bug description:
  xz segfaults. More details in
  https://bugs.launchpad.net/ubuntu/+source/initramfs-tools/+bug/2032379

  From Dmesg.txt on that report

  [114838.184191] xz[431483]: segfault at 7f9a93f3701a ip
  00007f9b3f780c1a sp 00007f9a957baa50 error 4 in
  liblzma.so.5.2.5[7f9b3f771000+1b000]

  ProblemType: Crash
  ApportVersion: 2.20.11-0ubuntu82.5
  Architecture: amd64
  CasperMD5CheckResult: unknown
  DistroRelease: Ubuntu 22.04
  ExecutablePath: /usr/bin/xz
  ExecutableTimestamp: 1649422298
  InstallationDate: Installed on 2021-04-09 (863 days ago)
  InstallationMedia: Ubuntu 20.04.2.0 LTS "Focal Fossa" - Release amd64 (20210209.1)
  Package: xz-utils 5.2.5-2ubuntu1
  ProcCmdline: xz --check=crc32 --threads=0 -c /var/tmp/mkinitramfs-MAIN_E1GbD9
  ProcCwd: /
  ProcEnviron:
   LC_CTYPE=C.UTF-8
   TERM=linux
   PATH=(custom, no user)
   LANG=en_GB.UTF-8
  ProcVersionSignature: Ubuntu 5.19.0-38.39~22.04.1-generic 5.19.17
  SegvAnalysis:
   Segfault happened at: 0x7f9b3f780c1a:	movzbl (%rdi,%r8,1),%r10d
   PC (0x7f9b3f780c1a) ok
   source "(%rdi,%r8,1)" (0x7f9a93f3701a) in non-readable VMA region: 0x7f9a90021000-0x7f9a94000000 ---p None
   destination "%r10d" ok
   Stack memory exhausted (SP below stack segment)
  SegvReason: reading VMA None
  Signal: 11
  SourcePackage: xz-utils
  Uname: Linux 5.19.0-38-generic x86_64
  UpgradeStatus: Upgraded to jammy on 2023-01-29 (204 days ago)
  UserGroups: N/A
  StacktraceTop:
   bt_find_func (len_limit=64, pos=9137198, cur=0x7f9a943edc3d "", cur_match=4194304, depth=24, son=son at entry=0x7f9a8afbd010, cyclic_pos=748589, cyclic_size=8388609, matches=0x7f9adc0ec324, len_best=11) at ../../../../src/liblzma/lz/lz_encoder_mf.c:483
   lzma_mf_bt4_find (mf=0x7f9a90000c70, matches=0x7f9adc0ec304) at ../../../../src/liblzma/lz/lz_encoder_mf.c:721
   lzma_mf_find (mf=mf at entry=0x7f9a90000c70, count_ptr=count_ptr at entry=0x7f9adc0ecb94, matches=matches at entry=0x7f9adc0ec304) at ../../../../src/liblzma/lz/lz_encoder_mf.c:28
   lzma_lzma_optimum_normal (position=<optimized out>, len_res=<synthetic pointer>, back_res=<synthetic pointer>, mf=<optimized out>, coder=<optimized out>) at ../../../../src/liblzma/lzma/lzma_encoder_optimum_normal.c:846
   lzma_lzma_optimum_normal (position=<optimized out>, len_res=<synthetic pointer>, back_res=<synthetic pointer>, mf=<optimized out>, coder=<optimized out>) at ../../../../src/liblzma/lzma/lzma_encoder_optimum_normal.c:804

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