netfilter: nf_tables: fix nft_cmp_fast failure on big endian for size < 4
nft_cmp_fast is used for equality comparisions of size <= 4. For
comparisions of size < 4 byte a mask is calculated that is applied to
both the data from userspace (during initialization) and the register
value (during runtime). Both values are stored using (in effect) memcpy
to a memory area that is then interpreted as u32 by nft_cmp_fast.
This works fine on little endian since smaller types have the same base
address, however on big endian this is not true and the smaller types
are interpreted as a big number with trailing zero bytes.
The mask therefore must not include the lower bytes, but the higher bytes
on big endian. Add a helper function that does a cpu_to_le32 to switch
the bytes on big endian. Since we're dealing with a mask of just consequitive
bits, this works out fine.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
diff --git a/net/netfilter/nft_cmp.c b/net/netfilter/nft_cmp.c
index 954925d..e2b3f51 100644
--- a/net/netfilter/nft_cmp.c
+++ b/net/netfilter/nft_cmp.c
@@ -128,7 +128,7 @@
BUG_ON(err < 0);
desc.len *= BITS_PER_BYTE;
- mask = ~0U >> (sizeof(priv->data) * BITS_PER_BYTE - desc.len);
+ mask = nft_cmp_fast_mask(desc.len);
priv->data = data.data[0] & mask;
priv->len = desc.len;
return 0;