Status changed to 'Confirmed' because the bug affects multiple users.
** Changed in: qemu (Ubuntu)
Status: New => Confirmed
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https://bugs.launchpad.net/bugs/1749393
Title:
sbrk() not working under qemu-user with a PIE-compiled binary?
Status in QEMU:
New
Status in qemu package in Ubuntu:
Confirmed
Bug description:
In Debian unstable, we recently switched bash to be a PIE-compiled
binary (for hardening). Unfortunately this resulted in bash being
broken when run under qemu-user (for all target architectures, host
being amd64 for me).
$ sudo chroot /srv/chroots/sid-i386/ qemu-i386-static /bin/bash
bash: xmalloc: .././shell.c:1709: cannot allocate 10 bytes (0 bytes allocated)
bash has its own malloc implementation based on sbrk():
https://git.savannah.gnu.org/cgit/bash.git/tree/lib/malloc/malloc.c
When we disable this internal implementation and rely on glibc's
malloc, then everything is fine. But it might be that glibc has a
fallback when sbrk() is not working properly and it might hide the
underlying problem in qemu-user.
This issue has also been reported to the bash upstream author and he
suggested that the issue might be in qemu-user so I'm opening a ticket here.
Here's the discussion with the bash upstream author:
https://lists.gnu.org/archive/html/bug-bash/2018-02/threads.html#00080
You can find the problematic bash binary in that .deb file:
http://snapshot.debian.org/archive/debian/20180206T154716Z/pool/main/b/bash/bash_4.4.18-1_i386.deb
The version of qemu I have been using is 2.11 (Debian package qemu-
user-static version 1:2.11+dfsg-1) but I have had reports that the
problem is reproducible with older versions (back to 2.8 at least).
Here are the related Debian bug reports:
https://bugs.debian.org/889869
https://bugs.debian.org/865599
It's worth noting that bash used to have this problem (when compiled as a PIE
binary) even when run directly but then something got fixed in the kernel and
now the problem only appears when run under qemu-user:
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1518483
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