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netfilter: x_tables: 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.  eacd86ca3b ("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@linux-foundation.org: coding-style fixes]
Fixes: eacd86ca3b ("net/netfilter/x_tables.c: use kvmalloc() in xt_alloc_tableLink: http://lkml.kernel.org/r/20180130140104.GE21609@dhcp22.suse.cz
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Michal Hocko 2018-01-30 11:30:11 -08:00 committed by Pablo Neira Ayuso
parent 743ffffefa
commit 0537250fdc
1 changed files with 6 additions and 1 deletions
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7
net/netfilter/x_tables.c
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@ -1008,7 +1008,12 @@ struct xt_table_info *xt_alloc_table_info(unsigned int size)
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;