Messages in this thread Patch in this message | | | Date | Tue, 5 Jun 2007 07:20:06 -0700 | From | "Anand Jahagirdar" <> | Subject | Re: Patch related with Fork Bombing Atack |
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Hello All I am forwarding one more improved patch related with fork bombing attack. I have used printk_ratelimit function in my patch and it works rellly well. it prints message as per printk_ratelimit values stored in /proc/sys/kernel/printk_ratelimit and /proc/sys/kernel/printk_ratelimit_burst. root can set printk_ratelimit values(such as how many times message should be repeated ,after how much time message should repeat) by making changes in the above 2 mentioned files. this patch will never flood syslog anymore and will definitely help administrator by informing him about fork bombing attack. added comments will help developers.
Regards, Anand
On 6/4/07, Daniel Hazelton <dhazelton@enter.net> wrote: > On Monday 04 June 2007 10:58:41 Jiri Kosina wrote: > > On Mon, 4 Jun 2007, Anand Jahagirdar wrote: > > > I am forwarding one improved patch related with Fork Bombing > > > Attack. This patch prints a message (only once) which alerts > > > administrator/root user about fork bombing attack. I created this patch > > > to implement my idea of informing administrator about fork bombing > > > attack on his machine only once. > > > This patch overcomes all drawbacks of my previous patch related with > > > fork bombing attack and helps administrator. added comments will > > > definitely help developers. > > > > > > + /* > > > + * following code prints a message which alerts administrator/root * > > > user about fork bombing Attack + */ > > > + if ((atomic_read(&p->user->processes) >= > > > (p->signal->rlim [RLIMIT_NPROC].rlim_cur - 1)) && > > > (atomic_read(&p->user->processes) < > > > p->signal->rlim[RLIMIT_NPROC].rlim_cur)) { > > > > Did this get malformed somehow? Looks like some successive lines got > > pasted together, or something. > > Seeing the lack of the '+' I think it's a mangling from not paying attention > to the 80 column marker in the editor. > > > > + if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && > > > p->user != &root_user) { + printk(KERN_CRIT"User with uid %d is > > > crossing its Process limit\n",p->user->uid); + } > > > + } > > > > Why not printk_ratelimit() here? Otherwise we have looped back to the > > possibility of user flooding the system logs, which has been already > > discussed in this thread, right? > > > > Also the { and } braces seem redundant. > They are. > > Here's two hints: > 1) double check for hidden "word wrap" problems. A sane programmers editor > will alert you to this, and careful checking of the patches before posting > will also reveal them. (emacs shows a \ in the 80th column, jed puts a $ > there, etc...) > 2) when there is a potential for syslog spam - like your patch has - use > printk_ratelimit() instead of printk(). This will throttle the output so that > flooding the syslog is no longer possible. > > DRH > ps: you patch is very difficult to apply - try using git > Index: root/Desktop/a1/linux-2.6.17.tar.bz2_FILES/linux-2.6.17/kernel/fork.c =================================================================== --- root.orig/Desktop/a1/linux-2.6.17.tar.bz2_FILES/linux-2.6.17/kernel/fork.c 2007-06-05 19:16:28.000000000 +0530 +++ root/Desktop/a1/linux-2.6.17.tar.bz2_FILES/linux-2.6.17/kernel/fork.c 2007-06-05 19:18:07.000000000 +0530 @@ -958,11 +958,18 @@ retval = -EAGAIN; + /* + * following code does not allow Non Root User to cross its process + * limit. it alerts administrator about fork bombing attack and prevents + * it. + */ if (atomic_read(&p->user->processes) >= p->signal->rlim[RLIMIT_NPROC].rlim_cur) if (!capable(CAP_SYS_ADMIN) && !capable(CAP_SYS_RESOURCE) && - p->user != &root_user) - + p->user != &root_user) { + if (printk_ratelimit()) + printk(KERN_CRIT"User with uid %d is crossing its process limit\n",p->user->uid); goto bad_fork_free; + } atomic_inc(&p->user->__count); | |