Patch "netfilter: x_tables: make allocation less aggressive" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

netfilter: x_tables: make allocation less aggressive

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
netfilter-x_tables-make-allocation-less-aggressive.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Michal Hocko <[email protected]>
Date: Tue, 30 Jan 2018 11:30:11 -0800
Subject: netfilter: x_tables: make allocation less aggressive

From: Michal Hocko <[email protected]>

commit 0537250fdc6c876ed4cbbe874c739aebef493ee2 upstream.

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.

---
 net/netfilter/x_tables.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

@@ -1008,7 +1008,12 @@ struct xt_table_info *xt_alloc_table_inf
 	if ((size >> PAGE_SHIFT) + 2 > totalram_pages)
 		return NULL;
 
-	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;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/netfilter-x_tables-make-allocation-less-aggressive.patch