Re: bash --noediting killed by O_NONBLOCK

[Chet Ramey]

Glynn Clements wrote:
> Configuration Information [Automatically generated, do not change]:
> Machine: i686
> OS: linux-gnu
> Compiler: i686-pc-linux-gnu-gcc
> Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i686' 
> -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i686-pc-linux-gnu' 
> -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL 
> -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib   -g -O2 -mtune=pentium-m -pipe
> uname output: Linux cerise 2.6.24.3 #2 SMP Thu Mar 27 10:43:06 GMT 2008 i686 
> GNU/Linux
> Machine Type: i686-pc-linux-gnu
>
> Bash Version: 3.2
> Patch Level: 33
> Release Status: release
>
> Description:
>
> If --noediting is used (e.g. for use with Emacs' shell-mode), and a
> program run from bash sets O_NONBLOCK on bash's stdin, bash reads and
> executes random garbags until it eventually segfaults.
>
> Repeat-By:
>
> bash --noediting
> <any program which leaves the descriptor in non-blocking mode>
>
> Fix:
>
> The attached patch appears to fix the specific problem. However, I'm
> still unclear as to how the original problem occurs. It looks as if
> the errno != EINTR check should result in a busy-wait.

Thanks for the patch.  There won't be a busy-wait if nothing's been
read into the local buffer:  local_bufused == 0 means that the function
will return EOF.

Chet

--
``The lyf so short, the craft so long to lerne.'' - Chaucer

Chet Ramey, ITS, CWRU    chet@case.edu    http://cnswww.cns.cwru.edu/~chet/