procfs stdio writev problem

[Jens <jensl@laas.mine.nu>]

Hello!

I've noticed a problem when using bash linked with musl.

laas:~# echo 60 > /proc/sys/kernel/panic
-su: echo: write error: Invalid argument

laas:~# cat t.sh
#!/bin/bash
echo 60 > /proc/sys/kernel/panic

laas:~# strace -f t.sh
...
writev(1, [{"60", 2}, {"\n", 1}], 2)    = 2
writev(1, [{"", 0}, {"\n", 1}], 2)      = -1 EINVAL (Invalid argument)

I'm guessing that musl uses writev in its stdio implementation.

And I think the error is due to a simplistic implementation in procfs, 
that parses each write on its own, and that the writev is split into 
several writes.

This is with linux kernel 3.6.0 btw.

I have no idea if something can and should be done about this, but likely 
somebody else will run into the same problem.

Regards,
Jens