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bug#26227: grep critical local DoS from userspace
From: |
bloodman |
Subject: |
bug#26227: grep critical local DoS from userspace |
Date: |
Fri, 24 Mar 2017 08:19:34 +0100 |
Hello,
Ah yes. Mea culpa. This, of course, may be a old bins/kernel/distro bug... ;]
address@hidden:~# cat /etc/debian_version
8.7
(upgraded)
address@hidden:~# cat /proc/version
Linux version 3.16.0-4-amd64 (address@hidden) (gcc version 4.8.4 (Debian
4.8.4-1) ) #1 SMP Debian 3.16.39-1+deb8u2 (2017-03-07)
address@hidden:~# grep -V
grep (GNU grep) 2.20
address@hidden:~# cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 42
model name : Intel(R) Xeon(R) CPU E31240 @ 3.30GHz
stepping : 7
microcode : 0x29
cpu MHz : 3292.508
cache size : 8192 KB
[...]
address@hidden:~# free
total used free shared buffers cached
Mem: 8152512 7972816 179696 44868 179012 7212820
-/+ buffers/cache: 580984 7571528
Swap: 7811068 48236 7762832
> tags 26227 moreinfo
> done
> On Thu, Mar 23, 2017 at 12:11 PM, <address@hidden> wrote:
>> Today I searched some files and... my server goes to hell (crash).
>>
>> replication:
>>
>> 0. log into root or user account (whatever)
>> 1. make a huge empty file (eg. 10 GB of zeros)
>> (my is: -rw-r--r-- 1 root root 10485760000 Feb 28 18:14 testfile.out)
>> 2. grep -Hi "\/tmp\/" * 2>/dev/null
>> 3. crash (probably due to out of memory)
> Thanks for the report, but...
> What version of grep are you using? The latest (grep-3.0) operates
> pretty quickly, and doesn't even use 3MB of RSS:
> $ dd status=none bs=1M count=10000 of=big < /dev/zero && env time
> grep -l x big
> 3.69user 1.10system 0:04.81elapsed 99%CPU (0avgtext+0avgdata
> 2388maxresident)k
> 0inputs+0outputs (0major+102minor)pagefaults 0swaps
--
Tomasz 'BloodMan' Tomkowiak