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

[Adrien Nader]

XZ developers have a couple questions regarding this after looking at the trace:
- is it reproducible? did it happen several times?
- does the machine use ECC memory?

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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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