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Re: tail aborts while following by name if using inotify
From: |
Jim Meyering |
Subject: |
Re: tail aborts while following by name if using inotify |
Date: |
Tue, 29 Dec 2009 17:03:30 +0100 |
Giuseppe Scrivano wrote:
> Subject: [PATCH] tail: remove `fdspec' from the hash table before change its
> key
>
> * src/tail.c (tail_forever_inotify): Avoid to modify fdspec->wd until it
> is contained in the wd_to_name hash table with a different key value.
> Once it is removed, it can be added using the new `wd' as key for the
> hash table.
> ---
> src/tail.c | 9 ++++++---
> 1 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/src/tail.c b/src/tail.c
> index 8e6c8ac..83b4253 100644
> --- a/src/tail.c
> +++ b/src/tail.c
> @@ -1474,15 +1474,18 @@ tail_forever_inotify (int wd, struct File_spec *f,
> size_t n_files,
> continue;
>
> /* It's fine to add the same file more than once. */
> - f[j].wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask);
> -
> - if (f[j].wd < 0)
> + int new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask);
> + if (new_wd < 0)
> {
> error (0, errno, _("cannot watch %s"), quote (f[j].name));
> continue;
> }
>
> fspec = &(f[j]);
> +
> + /* Remove `fspec' and re-add it using `new_fd' as its key. */
> + hash_delete (wd_to_name, fspec);
> + f[j].wd = new_wd;
Thanks again. I've just pushed your fix, along with the two
corresponding tests that now pass. I've made one small change:
I prefer to use fspec-> rather than the technically equivalent f[j]. here:
- f[j].wd = new_wd;
+ fspec->wd = new_wd;
>From 07f15147eb72e9c60686068ddea9c6c5b1ac62e3 Mon Sep 17 00:00:00 2001
From: Giuseppe Scrivano <address@hidden>
Date: Tue, 29 Dec 2009 14:59:24 +0100
Subject: [PATCH 1/3] tail: remove `fdspec' from the hash table before changing
its key
* src/tail.c (tail_forever_inotify): Avoid modifying fdspec->wd while
it is in the wd_to_name hash table. Once it is removed, it can be
added using the new `wd' as key for the hash table. This fixes the
abort-inducing bug reported by Rob Wortman in
http://thread.gmane.org/gmane.comp.gnu.coreutils.bugs/19372
---
src/tail.c | 9 ++++++---
1 files changed, 6 insertions(+), 3 deletions(-)
diff --git a/src/tail.c b/src/tail.c
index 8e6c8ac..3d5e221 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -1474,15 +1474,18 @@ tail_forever_inotify (int wd, struct File_spec *f,
size_t n_files,
continue;
/* It's fine to add the same file more than once. */
- f[j].wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask);
-
- if (f[j].wd < 0)
+ int new_wd = inotify_add_watch (wd, f[j].name, inotify_wd_mask);
+ if (new_wd < 0)
{
error (0, errno, _("cannot watch %s"), quote (f[j].name));
continue;
}
fspec = &(f[j]);
+
+ /* Remove `fspec' and re-add it using `new_fd' as its key. */
+ hash_delete (wd_to_name, fspec);
+ fspec->wd = new_wd;
if (hash_insert (wd_to_name, fspec) == NULL)
xalloc_die ();
--
1.6.6.301.g5794
>From bd26efaaa3e251c4a1bed308ec5ee500ecfd7d25 Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Mon, 28 Dec 2009 15:42:10 +0100
Subject: [PATCH 2/3] tail: add a test to exercise abort-inducing flaw in tail -F
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
* tests/tail-2/inotify-hash-abuse: New file, derived from
a report by Rob Wortman.
* tests/Makefile.am (TESTS): Add it.
Improved by: Pádraig Brady.
---
THANKS | 1 +
tests/Makefile.am | 1 +
tests/tail-2/inotify-hash-abuse | 69 +++++++++++++++++++++++++++++++++++++++
3 files changed, 71 insertions(+), 0 deletions(-)
create mode 100755 tests/tail-2/inotify-hash-abuse
diff --git a/THANKS b/THANKS
index 668d59f..86be252 100644
--- a/THANKS
+++ b/THANKS
@@ -512,6 +512,7 @@ Richard Sharman address@hidden
Rick Sladkey address@hidden
Rik Faith address@hidden
Risto Kankkunen address@hidden
+Rob Wortman address@hidden
Robert H. de Vries address@hidden
Robert Lindgren address@hidden
Robert Millan address@hidden
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 93d4275..35ea8b2 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -80,6 +80,7 @@ TESTS = \
rm/ext3-perf \
rm/cycle \
cp/link-heap \
+ tail-2/inotify-hash-abuse \
tail-2/inotify-rotate \
chmod/no-x \
chgrp/basic \
diff --git a/tests/tail-2/inotify-hash-abuse b/tests/tail-2/inotify-hash-abuse
new file mode 100755
index 0000000..bc86398
--- /dev/null
+++ b/tests/tail-2/inotify-hash-abuse
@@ -0,0 +1,69 @@
+#!/bin/sh
+# Exercise an abort-inducing flaw in inotify-enabled tail -F.
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ tail --version
+fi
+
+. $srcdir/test-lib.sh
+
+# 9 is a magic number, related to internal details of tail.c and hash.c
+n=9
+seq $n | xargs touch || framework_failure
+
+debug='---disable-inotify -s .01'
+debug=
+tail $debug -qF $(seq $n) > out 2>&1 & pid=$!
+
+# Wait until tail has started...
+echo x > $n
+until grep '^x$' out >/dev/null 2>&1; do :; done
+
+mv 1 f || fail=1
+
+# Wait for this diagnostic:
+# tail: `1' has become inaccessible: No such file or directory
+until grep inaccessible out >/dev/null 2>&1; do :; done
+
+# Trigger the bug. Before the fix, this would provoke the abort.
+echo a > 1 || fail=1
+
+# Wait up to 2s for the buggy tail to die,
+# or for the "tail: `1' has appeared; following end of new file" output
+dead=0
+for i in $(seq 10); do
+ kill -0 $pid || { dead=1; break; }
+ grep 'has appeared;' out > /dev/null && break
+ sleep .2
+done
+
+# Fixed tail will not have aborted. Kill it.
+test $dead = 0 && kill -HUP $pid
+
+wait $pid
+st=$?
+
+case $st in
+ 129) ;;
+ *) echo tail died via unexpected signal: $st; fail=1;;
+esac
+
+cat out
+
+Exit $fail
--
1.6.6.301.g5794
>From fd93fc3ef4947f4712a4bda08b6e11c0d6cdf48a Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Tue, 29 Dec 2009 13:47:10 +0100
Subject: [PATCH 3/3] tail: add another test to exercise abort-inducing flaw in
tail -F
* tests/tail-2/inotify-hash-abuse2: New test, based on a reproducer
by Rob Wortman.
* tests/Makefile.am (TESTS): Add it.
---
tests/Makefile.am | 1 +
tests/tail-2/inotify-hash-abuse2 | 50 ++++++++++++++++++++++++++++++++++++++
2 files changed, 51 insertions(+), 0 deletions(-)
create mode 100755 tests/tail-2/inotify-hash-abuse2
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 35ea8b2..6ef7ad8 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -81,6 +81,7 @@ TESTS = \
rm/cycle \
cp/link-heap \
tail-2/inotify-hash-abuse \
+ tail-2/inotify-hash-abuse2 \
tail-2/inotify-rotate \
chmod/no-x \
chgrp/basic \
diff --git a/tests/tail-2/inotify-hash-abuse2 b/tests/tail-2/inotify-hash-abuse2
new file mode 100755
index 0000000..2f59eb4
--- /dev/null
+++ b/tests/tail-2/inotify-hash-abuse2
@@ -0,0 +1,50 @@
+#!/bin/sh
+# Exercise an abort-inducing flaw in inotify-enabled tail -F.
+# Like inotify-hash-abuse, but without a hard-coded "9".
+
+# Copyright (C) 2009 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+if test "$VERBOSE" = yes; then
+ set -x
+ tail --version
+fi
+
+. $srcdir/test-lib.sh
+
+touch f || framework_failure
+
+debug='---disable-inotify -s .001'
+debug=
+timeout 10 tail $debug -F f & pid=$!
+
+for i in $(seq 200); do
+ kill -0 $pid || break;
+ mv f g
+ touch f
+done
+
+# Fixed tail will not have aborted. Kill it.
+kill -HUP $pid
+
+wait $pid
+st=$?
+
+case $st in
+ 129) ;;
+ *) echo tail died via unexpected signal: $st; fail=1;;
+esac
+
+Exit $fail
--
1.6.6.301.g5794