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netfilter: ipset: fix unaligned atomic access 

When using ip_set with counters and comment, traffic causes the kernel
to panic on 32-bit ARM:

Alignment trap: not handling instruction e1b82f9f at [<bf01b0dc>]
Unhandled fault: alignment exception (0x221) at 0xea08133c
PC is at ip_set_match_extensions+0xe0/0x224 [ip_set]

The problem occurs when we try to update the 64-bit counters - the
faulting address above is not 64-bit aligned.  The problem occurs
due to the way elements are allocated, for example:

	set->dsize = ip_set_elem_len(set, tb, 0, 0);
	map = ip_set_alloc(sizeof(*map) + elements * set->dsize);

If the element has a requirement for a member to be 64-bit aligned,
and set->dsize is not a multiple of 8, but is a multiple of four,
then every odd numbered elements will be misaligned - and hitting
an atomic64_add() on that element will cause the kernel to panic.

ip_set_elem_len() must return a size that is rounded to the maximum
alignment of any extension field stored in the element.  This change
ensures that is the case.

Fixes: 95ad1f4a93 ("netfilter: ipset: Fix extension alignment")
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Russell King 2020-06-10 21:51:11 +01:00 committed by Pablo Neira Ayuso
parent 67c20de35a
commit 7150284600
1 changed files with 2 additions and 0 deletions
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2
net/netfilter/ipset/ip_set_core.c
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@ -460,6 +460,8 @@ ip_set_elem_len(struct ip_set *set, struct nlattr *tb[], size_t len,
for (id = 0; id < IPSET_EXT_ID_MAX; id++) {
if (!add_extension(id, cadt_flags, tb))
continue;
if (align < ip_set_extensions[id].align)
align = ip_set_extensions[id].align;
len = ALIGN(len, ip_set_extensions[id].align);
set->offset[id] = len;
set->extensions |= ip_set_extensions[id].type;