From: Patrick McHardy <[email protected]> upstream commit b855d416dc17061ebb271ea7ef1201d100531770
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. Cc: <[email protected]> # 3.14.x Signed-off-by: Patrick McHardy <[email protected]> Signed-off-by: Pablo Neira Ayuso <[email protected]> --- 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(-) diff --git a/include/net/netfilter/nf_tables_core.h b/include/net/netfilter/nf_tables_core.h index cf2b7ae..a75fc8e 100644 --- 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); diff --git a/net/netfilter/nf_tables_core.c b/net/netfilter/nf_tables_core.c index 90998a6..8041053 100644 --- 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 struct nft_expr *expr, 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; 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 @@ static int nft_cmp_fast_init(const struct nft_ctx *ctx, 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; -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
