Re: Re: [PATCH] linux-user: Make TARGET_NR_setgroups affect only the current thread

[Ilya Leoshkevich]

On Wed, Jan 31, 2024 at 08:53:49AM +0100, Helge Deller wrote:
> On 1/31/24 01:18, Ilya Leoshkevich wrote:
> > Like TARGET_NR_setuid, TARGET_NR_setgroups should affect only the
> > calling thread, and not the entire process. Therefore, implement it
> > using a syscall, and not a libc call.
> > 
> > Cc: qemu-stable@nongnu.org
> > Fixes: 19b84f3c35d7 ("added setgroups and getgroups syscalls")
> > Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
> 
> Patch seems ok, but just out of interest, how did you noticed?
> 
> Helge

Our internal users are trying to emulate a larger app, and they were
running into weird crashes between fork() and exec(). I had to
implement syscall catchpoints (posted) and follow-fork-mode child
(still needs a few cleanups before I can post it) to be able to debug
it, and found it was dying here [1], and from there it was easy.

[1] 
https://sourceware.org/git/?p=glibc.git;a=blob;f=nptl/nptl_setxid.c;h=4bfcfe41882d9b15b8090325bfdc9ceb5ab2693e;hb=36f2487f13e3540be9ee0fb51876b1da72176d3f#l25