linux-kernel - [PATCH] netfilter: avoid warn and OOM on vmalloc call

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Message-Id: <6fd343e83c26c5108d4b6c189e434a5a6e7ebd01.1480534469.git.marcelo.leitner@gmail.com>
Date:   Wed, 30 Nov 2016 17:42:22 -0200
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     andreyknvl@...gle.com
Cc:     fw@...len.de, nhorman@...driver.com, netdev@...r.kernel.org,
        netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] netfilter: avoid warn and OOM on vmalloc call

Hi Andrey,

Please let me know how this works for you. It seems good here, though
your poc may still trigger OOM through other means.

Thanks,
Marcelo

---8<---

Andrey Konovalov reported that this vmalloc call is based on an
userspace request and that it's spewing traces, which may flood the logs
and cause DoS if abused.

Florian Westphal also mentioned that this call should not trigger OOM,
as kmalloc one is already not triggering it.

This patch brings the vmalloc call in sync to kmalloc and disables the
warn trace on allocation failure and also disable OOM invocation.

Note, however, that under such stress situation, other places may
trigger OOM invocation.

Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
Cc: Florian Westphal <fw@...len.de>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
---
 net/netfilter/x_tables.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netfilter/x_tables.c b/net/netfilter/x_tables.c
index fc4977456c30e098197b4f987b758072c9cf60d9..dece525bf83a0098dad607fce665cd0bde228362 100644
--- a/net/netfilter/x_tables.c
+++ b/net/netfilter/x_tables.c
@@ -958,7 +958,9 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
 	if (sz <= (PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER))
 		info = kmalloc(sz, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY);
 	if (!info) {
-		info = vmalloc(sz);
+		info = __vmalloc(sz, GFP_KERNEL | __GFP_NOWARN |
+				     __GFP_NORETRY | __GFP_HIGHMEM,
+				 PAGE_KERNEL);
 		if (!info)
 			return NULL;
 	}
-- 
2.9.3