Debian Bug report logs - #642504
bash: file number exhaustion on certain redirections in loop: "Too many open files"

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Valentin Hilbig <debian-bug-reply@03.softkill.org>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: bash: file number exhaustion on certain redirections in loop: "Too many open files"

Date: Fri, 23 Sep 2011 08:22:35 +0200

Package: bash
Version: 4.1-3
Severity: normal


Attached is bashbug.sh which shows a strange bug in bash - with workaround.

The problem seems to be that certain redirections are not closed in-time,
leading to a possible exhaustion of file descriptors when doing this
redirection in a loop.

The strange thing about this is, that the file descriptors are closed
later, when it is already too late.

There is a workaround, this is to close the redirection manually.
However technically this is wrong, as at the time of the close the
redirection is no more in effect.

Possibly this is an upstream problem, I did not test it.

-- System Information:
Debian Release: 6.0.2
  APT prefers oldstable
  APT policy: (500, 'oldstable'), (500, 'stable')
Architecture: i386 (i686)

Kernel: Linux 2.6.26-2-686 (SMP w/1 CPU core)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/bash

Versions of packages bash depends on:
ii  base-files                6.0squeeze2    Debian base system miscellaneous f
ii  dash                      0.5.5.1-7.4    POSIX-compliant shell
ii  debianutils               3.4            Miscellaneous utilities specific t
ii  libc6                     2.11.2-10      Embedded GNU C Library: Shared lib
ii  libncurses5               5.7+20100313-5 shared libraries for terminal hand

Versions of packages bash recommends:
pn  bash-completion               <none>     (no description available)

Versions of packages bash suggests:
pn  bash-doc                      <none>     (no description available)

-- no debconf information

*** bashbug.sh
#!/bin/bash
#
# Out of file descriptors, because it forgets to close redirection

bug()
{
c=`ulimit -n`
let c+=100
while let c--
do
	while read -ru3 x
	do
		echo -n :
	done 3< <(echo x)

	# Workaround:
	# Explicite close of redirection
	$1 || exec 3<&-
done
}

works()
{
c=`ulimit -n`
let c+=100
while let c--
do
	while read -ru3 x
	do
		echo -n :
	done 3<<<"x"
done
}


echo "triggering bug"
bug true

echo "run with bug workaround"
bug false

echo "different redirection"
works

Message #10 received at 642504@bugs.debian.org (full text, mbox, reply):

From: Antoine Beaupré <anarcat@debian.org>

To: Valentin Hilbig <debian-bug-reply@03.softkill.org>, 642504@bugs.debian.org

Subject: Re: Bug#642504: bash: file number exhaustion on certain redirections in loop: "Too many open files"

Date: Fri, 26 Apr 2024 14:47:29 -0400

I saw a similar crash here, where bash would start failing around about
500 iterations in such a loop:

```
export GIT_ASKPASS=echo

grep -v '^#' ../gitolite2gitlab.txt |while read gitolite_path gitlab_path; do
    gitolite_url=/srv/git.torproject.org/repositories/$gitolite_path.git 
    gitlab_url=https://gitlab.torproject.org/$gitlab_path.git 
    echo "diff -u $gitolite_url $gitlab_url"
    diff -u <(git ls-remote $gitolite_url) <(git ls-remote $gitlab_url)
done | tee final-remote-diff.patch
```

~500 is not a random number. it's about half of 1024, which i suspect is
the fd limit i'm hitting. i'm betting the shell is just not closing
those file descriptor at all after the pipeline completes.

normally, i would expect the FD to close after the `diff -u` command
returns there, but it seems that's just not happening.

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