[Bug 1779955] Re: qemu linux-user requires read permissions on memory passed to syscalls that should only need write access

[Thomas Huth]

This is an automated cleanup. This bug report has been moved to QEMU's
new bug tracker on gitlab.com and thus gets marked as 'expired' now.
Please continue with the discussion here:

 https://gitlab.com/qemu-project/qemu/-/issues/470


** Changed in: qemu
       Status: Confirmed => Expired

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #470
   https://gitlab.com/qemu-project/qemu/-/issues/470

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https://bugs.launchpad.net/bugs/1779955

Title:
  qemu linux-user requires read permissions on memory passed to syscalls
  that should only need write access

Status in QEMU:
  Expired

Bug description:
  When read() function takes an mmap'ed address as output buffer, it
  returns EFAULT. The expected behavior is it should just work.

  The following code works for qemu-system-arm, but not for qemu-arm-
  static.

  QEMU version affected: latest release 2.12.0.

  Steps to reproduce (please substitute /path/to/qemu-arm-static with
  the path of the binary, and /tmp/a.cpp with the example source code
  attached):

  # First register binfmt_misc
  [hidden]$ docker run --rm --privileged multiarch/qemu-user-static:register 
--reset

  # Compile the code and run
  [hidden]$ docker run --rm -it -v /tmp/a.cpp:/tmp/a.cpp -v 
/path/to/qemu-arm-static:/usr/bin/qemu-arm-static arm32v7/ubuntu:18.04 bash -c 
'{ apt update -y && apt install -y g++; } >& /dev/null && g++ -std=c++14 
/tmp/a.cpp -o /tmp/a.out && echo hehe > /tmp/haha.txt && /tmp/a.out'
  ofd=3
  ftruncate=0
  mmap=0xff3f5000
  fd=4
  0xff3f5023 -1 14

  The expected result in qemu-system-arm as well as natively on x86_64 host:
  hidden$ ./a.out
  ofd=3
  ftruncate=0
  mmap=0xb6fb7000
  fd=4
  0xb6fb7023 5 0

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