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.
Signed-off-by: Russell King <rmk+kernel@xxxxxxxxxxxxxxx>
---
Patch against v5.6, where I tripped over this bug. This bug has
caused a kernel panic on my new router twice today.
net/netfilter/ipset/ip_set_core.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
index 8dd17589217d..be9cd6a500fb 100644
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -459,6 +459,8 @@ 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;
--
2.20.1
