Re: [Bug 215813] syscall(SYS_vfork) causes execve() to return 0. (was: vfork(2) behavior not consistent with fork(2))

Alejandro Colomar <alx.manpages@xxxxxxxxx> · Wed, 6 Apr 2022 21:31:57 +0200

Hi Florian,

On 4/6/22 21:26, Florian Weimer wrote:
It's not clear if this is valid.  The syscall function in glibc does not
protect the on-stack return address against overwriting, so it can't be
used to call SYS_vfork on x86.

Can you reproduce this with a true inline syscall, or the glibc vfork
function (which protects the return address)?

If you tell me how I can call a syscall without the libc wrapper or 
syscall(2), sure, I can try :)

If syscall(2) can't be used for certain syscalls, maybe we should 
document that.

Thanks,

Alex