Re: [netfilter-core] kernel panic: Out of memory and no killable processes... (2)
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2018-01-30 19:27:51
Also in:
linux-mm, lkml, netfilter-devel
On Tue, 30 Jan 2018 15:01:04 +0100 Michal Hocko [off-list ref] wrote:
quoted
Well, this is not about syzkaller, it merely pointed out a potential DoS... And that has to be addressed somehow.So how about this? ---
argh ;)
quoted hunk ↗ jump to hunk
quoted
From d48e950f1b04f234b57b9e34c363bdcfec10aeee Mon Sep 17 00:00:00 2001From: Michal Hocko <mhocko@suse.com> Date: Tue, 30 Jan 2018 14:51:07 +0100 Subject: [PATCH] net/netfilter/x_tables.c: make allocation less aggressive syzbot has noticed that xt_alloc_table_info can allocate a lot of memory. This is an admin only interface but an admin in a namespace is sufficient as well. eacd86ca3b03 ("net/netfilter/x_tables.c: use kvmalloc() in xt_alloc_table_info()") has changed the opencoded kmalloc->vmalloc fallback into kvmalloc. It has dropped __GFP_NORETRY on the way because vmalloc has simply never fully supported __GFP_NORETRY semantic. This is still the case because e.g. page tables backing the vmalloc area are hardcoded GFP_KERNEL. Revert back to __GFP_NORETRY as a poors man defence against excessively large allocation request here. We will not rule out the OOM killer completely but __GFP_NORETRY should at least stop the large request in most cases. Fixes: eacd86ca3b03 ("net/netfilter/x_tables.c: use kvmalloc() in xt_alloc_table_info()") Signed-off-by: Michal Hocko <mhocko@suse.com> --- net/netfilter/x_tables.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-)diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c index d8571f414208..a5f5c29bcbdc 100644 --- a/net/netfilter/x_tables.c +++ b/net/netfilter/x_tables.c@@ -1003,7 +1003,13 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size) if ((SMP_ALIGN(size) >> PAGE_SHIFT) + 2 > totalram_pages) return NULL;
offtopic: preceding comment here is "prevent them from hitting BUG() in vmalloc.c". I suspect this is ancient code and vmalloc sure as heck shouldn't go BUG with this input. And it should be using `sz' ;) So I suspect and hope that this code can be removed. If not, let's fix vmalloc!
- info = kvmalloc(sz, GFP_KERNEL); + /* + * __GFP_NORETRY is not fully supported by kvmalloc but it should + * work reasonably well if sz is too large and bail out rather + * than shoot all processes down before realizing there is nothing + * more to reclaim. + */ + info = kvmalloc(sz, GFP_KERNEL | __GFP_NORETRY); if (!info) return NULL;
checkpatch sayeth networking block comments don't use an empty /* line, use /* Comment... So I'll do that and shall scoot the patch Davewards. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>