> Brad Spengler published a local memory-allocation DoS that > evades the OOM-killer (though not the virtual memory RLIMIT): > http://www.grsecurity.net/~spender/64bit_dos.c > > execve()->copy_strings() can allocate a lot of memory, but > this is not visible to oom-killer, nobody can see the nascent > bprm->mm and take it into account. > > With this patch get_arg_page() increments current's MM_ANONPAGES > counter every time we allocate the new page for argv/envp. When > do_execve() succeds or fails, we change this counter back. > > Technically this is not 100% correct, we can't know if the new > page is swapped out and turn MM_ANONPAGES into MM_SWAPENTS, but > I don't think this really matters and everything becomes correct > once exec changes ->mm or fails. > > Reported-by: Brad Spengler <spender@xxxxxxxxxxxxxx> > By-discussion-with: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> > Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Looks good to me. Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> Thank you very much. > --- K/fs/exec.c~acct_exec_mem 2010-11-30 18:27:15.000000000 +0100 > +++ K/fs/exec.c 2010-11-30 18:28:54.000000000 +0100 > @@ -164,6 +164,25 @@ out: > > #ifdef CONFIG_MMU > > +static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages) One minor request. I guess this function can easily makes confusing to a code reader. So I hope you write small function comments. describe to - What is oom nascent issue - Why we think inaccurate account is ok > +{ > + struct mm_struct *mm = current->mm; > + long diff = (long)(pages - bprm->vma_pages); > + > + if (!mm || !diff) > + return; > + > + bprm->vma_pages = pages; > + > +#ifdef SPLIT_RSS_COUNTING > + add_mm_counter(mm, MM_ANONPAGES, diff); > +#else > + spin_lock(&mm->page_table_lock); > + add_mm_counter(mm, MM_ANONPAGES, diff); > + spin_unlock(&mm->page_table_lock); > +#endif > +} > + -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>