| From b855d416dc17061ebb271ea7ef1201d100531770 Mon Sep 17 00:00:00 2001 |
| From: Patrick McHardy <kaber@trash.net> |
| Date: Sat, 12 Apr 2014 13:17:57 +0200 |
| Subject: netfilter: nf_tables: fix nft_cmp_fast failure on big endian for size < 4 |
| |
| From: Patrick McHardy <kaber@trash.net> |
| |
| commit b855d416dc17061ebb271ea7ef1201d100531770 upstream. |
| |
| 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> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| include/net/netfilter/nf_tables_core.h | 10 ++++++++++ |
| net/netfilter/nf_tables_core.c | 3 +-- |
| net/netfilter/nft_cmp.c | 2 +- |
| 3 files changed, 12 insertions(+), 3 deletions(-) |
| |
| --- a/include/net/netfilter/nf_tables_core.h |
| +++ b/include/net/netfilter/nf_tables_core.h |
| @@ -13,6 +13,16 @@ struct nft_cmp_fast_expr { |
| u8 len; |
| }; |
| |
| +/* Calculate the mask for the nft_cmp_fast expression. On big endian the |
| + * mask needs to include the *upper* bytes when interpreting that data as |
| + * something smaller than the full u32, therefore a cpu_to_le32 is done. |
| + */ |
| +static inline u32 nft_cmp_fast_mask(unsigned int len) |
| +{ |
| + return cpu_to_le32(~0U >> (FIELD_SIZEOF(struct nft_cmp_fast_expr, |
| + data) * BITS_PER_BYTE - len)); |
| +} |
| + |
| extern const struct nft_expr_ops nft_cmp_fast_ops; |
| |
| int nft_cmp_module_init(void); |
| --- a/net/netfilter/nf_tables_core.c |
| +++ b/net/netfilter/nf_tables_core.c |
| @@ -25,9 +25,8 @@ static void nft_cmp_fast_eval(const stru |
| struct nft_data data[NFT_REG_MAX + 1]) |
| { |
| const struct nft_cmp_fast_expr *priv = nft_expr_priv(expr); |
| - u32 mask; |
| + u32 mask = nft_cmp_fast_mask(priv->len); |
| |
| - mask = ~0U >> (sizeof(priv->data) * BITS_PER_BYTE - priv->len); |
| if ((data[priv->sreg].data[0] & mask) == priv->data) |
| return; |
| data[NFT_REG_VERDICT].verdict = NFT_BREAK; |
| --- a/net/netfilter/nft_cmp.c |
| +++ b/net/netfilter/nft_cmp.c |
| @@ -128,7 +128,7 @@ static int nft_cmp_fast_init(const struc |
| 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; |