do_exec_pty(..)

[mouring at etoh.eviladmin.org]

On Wed, 28 Feb 2001, Sunil K. Vallamkonda wrote:

> Hello,
> 
> I see that incase of command execution:
> :fork()" is called twice, in sshd.
> Once to spin off child sshd from parenat and 
> second from child sshd, to execute command.
> Due to this I see 3 processes being created
> for each connection viz:
> 
> 16398  0.0  0.3  1284  892 ??  S     4:33PM    0:00.05 sshd:child
> 16399  0.0  0.1   320  232 p4  Is+   4:33PM    0:00.06 -sh -c foo_command
> 16401  0.0  0.3  2076  840 p4  S+    4:33PM    0:00.01 foo_command
> 
> I may be missing something, but
> I was wondering to why second
> fork() is required to execute a command
> on server. 
> To execute a command, the child sshd could execve(..).
> thus eliminate the need for second fork() and possibly
> simpler code path.
> 

I don't follow.

do_exec_pty()  forks.. and the child calls do_child()  which goes through
a bunch of security and environmental hoops then execve(...).  Which runs
'sh -c ..' then sh itself forks to run the -c command.  

I don't see how it's sshd fault that sh forks() on -c stead of doing a
exec*().

- Ben