From: Michal Hocko <mhocko@xxxxxxxxxx>
Subject: 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.
[akpm@xxxxxxxxxxxxxxxxxxxx: coding-style fixes]
Fixes: eacd86ca3b03 ("net/netfilter/x_tables.c: use kvmalloc() in xt_alloc_tableLink: http://lkml.kernel.org/r/20180130140104.GE21609@xxxxxxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Florian Westphal <fw@xxxxxxxxx>
Reviewed-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
net/netfilter/x_tables.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff -puN net/netfilter/x_tables.c~net-netfilter-x_tablesc-make-allocation-less-aggressive net/netfilter/x_tables.c
--- a/net/netfilter/x_tables.c~net-netfilter-x_tablesc-make-allocation-less-aggressive
+++ a/net/netfilter/x_tables.c
@@ -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;
_
--
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