Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes:
> On Wed, 10 Dec 2014 16:49:18 +0300 Dmitry Monakhov <dmonakhov@xxxxxxxxxx> wrote:
>
>>
>> Hello. Someone please take care of this patch.
>>
>> W/o that patch unprivileged user may abuse system resources simply by spawning
>> wast number of unkilable busyloops (works on ext2/ext3):
>>
>> truncate --size 1T test
>> for ((i=0;i<1024;i++))
>> do
>> filefrag test > /dev/null &
>> done
>>
>> >> --- a/fs/ioctl.c
>> >> +++ b/fs/ioctl.c
>> >> @@ -379,6 +379,11 @@ int __generic_block_fiemap(struct inode *inode,
>> >> past_eof = true;
>> >> }
>> >> cond_resched();
>> >> + if (fatal_signal_pending(current)) {
>> >> + ret = -EINTR;
>> >> + break;
>> >> + }
>> >> +
>> >> } while (1);
>> >>
>
> Is FIEMAP documented anywhere (manpage)? If so, that will need an
> update.
Yes you right. I just thought that it is assumed by default.
The only place I know is Documentation/filesystems/fiemap.txt
Please fold patch attached to original one.
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>From f7af425b2ac920065491a478b4f4359f422b3453 Mon Sep 17 00:00:00 2001
From: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
Date: Fri, 19 Dec 2014 13:11:29 +0400
Subject: [PATCH] doc: fimemap update signal behaviour
Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
---
Documentation/filesystems/fiemap.txt | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/Documentation/filesystems/fiemap.txt b/Documentation/filesystems/fiemap.txt
index 1b805a0..f6d9c99 100644
--- a/Documentation/filesystems/fiemap.txt
+++ b/Documentation/filesystems/fiemap.txt
@@ -196,7 +196,8 @@ struct fiemap_extent_info {
};
It is intended that the file system should not need to access any of this
-structure directly.
+structure directly. Filesystem handlers should be tolerant to signals and return
+EINTR once fatal signal received.
Flag checking should be done at the beginning of the ->fiemap callback via the
--
1.7.1
