URL: <https://savannah.gnu.org/bugs/?67624>
Summary: echo: write error: Invalid argument
Group: The GNU Bourne-Again SHell
Submitter: peppergrayxyz
Submitted: Thu 23 Oct 2025 11:35:32 PM UTC
Category: None
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: None
Status: None
Privacy: Public
Assigned to: None
Open/Closed: Open
Discussion Lock: Any
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Follow-up Comments:
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Date: Thu 23 Oct 2025 11:35:32 PM UTC By: Pepper Gray <peppergrayxyz>
Writing to the kernel causes an error, when appending '\n', when bash is
linked against musl. e.g.:
- register binfmt
> # printf '%s\n'
> ':qemu-riscv64:M::\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\xf3\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-riscv64:'"${QEMU_BINFMT_FLAGS}"
>>/proc/sys/fs/binfmt_misc/register"
> bash: line 1: printf: write error: Invalid argument
- unregister binfmt
> # strace -f -o 'strace-remove.log' bash -c 'echo "-1" >
> /proc/sys/fs/binfmt_misc/qemu-riscv64'
> bash: line 1: echo: write error: Invalid argument
This behavior seems to be present for a long time:
https://www.openwall.com/lists/musl/2013/05/05/1
Commands that cause the error:
-printf '%s\n', echo '..' on musl
Commands that work:
-printf '%s', echo -n '..' on musl
-printf '%s\n', echo '..' on glibc
-all commands work on sh and zsh (glibc and musl)
Traces for the failing commands are available in the downstream bug report:
https://bugs.gentoo.org/964994
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