[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Qemu-devel] [Bug 1779955] Re: qemu linux-user requires read permissions
From: |
Ke Liu |
Subject: |
[Qemu-devel] [Bug 1779955] Re: qemu linux-user requires read permissions on memory passed to syscalls that should only need write access |
Date: |
Thu, 12 Jul 2018 19:26:01 -0000 |
Thanks Peter for your information.
I was hit by the bug when trying to compile bazel (a build system open-
sourced by Google: https://bazel.build) and the code is at
https://github.com/bazelbuild/bazel/blob/master/third_party/ijar/mapped_file_unix.cc#L116
Of course I can send PR to fix that in bazel source, but I would say it
is not true that "in practice no guest binaries set up memory that is
only writable and can't be read". It is legitimate requirement and
coding practice.
--
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
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:
Confirmed
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
To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1779955/+subscriptions