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Re: Leak in BASH "named" file descriptors?


From: Andreas Schwab
Subject: Re: Leak in BASH "named" file descriptors?
Date: Thu, 28 Jan 2016 14:58:29 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux)

Greg Wooledge <address@hidden> writes:

> On Wed, Jan 27, 2016 at 01:18:11PM -0500, Mathieu Patenaude wrote:
>> When using "named" file descriptors inside a function, the file descriptors
>> are not automatically un-linked when the function returns, but when using
>> regular "numbered" file descriptors they are automatically "destroyed".
>
> Could not reproduce in an interactive shell, on bash 4.3.30 (Debian).
>
> $ f() { local fd; exec {fd}</dev/null; }
> $ f
> $ g() { exec 9</dev/null; }
> $ g
> $ lsof -p $$
> ...
> bash    931 wooledg    0u   CHR  136,0      0t0       3 /dev/pts/0
> bash    931 wooledg    1u   CHR  136,0      0t0       3 /dev/pts/0
> bash    931 wooledg    2u   CHR  136,0      0t0       3 /dev/pts/0
> bash    931 wooledg    9r   CHR    1,3      0t0    1028 /dev/null
> bash    931 wooledg   10r   CHR    1,3      0t0    1028 /dev/null
> bash    931 wooledg  255u   CHR  136,0      0t0       3 /dev/pts/0
>
> I actually ran the lsof multiple times, in between the calls to f and g.
> FD 10 was opened by f (and kept open), and FD 9 was of course opened by g
> (and kept open).

Try replacing exec with :.  Redirections established with exec are
always permanent.

Andreas.

-- 
Andreas Schwab, SUSE Labs, address@hidden
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE  1748 E4D4 88E3 0EEA B9D7
"And now for something completely different."



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