6.6-stable review patch. If anyone has any objections, please let me know.
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From: Florian Westphal fw@strlen.de
[ Upstream commit 14fb07130c7ddd257e30079b87499b3f89097b09 ]
Reject rules where a load occurs from a register that has not seen a store early in the same rule.
commit 4c905f6740a3 ("netfilter: nf_tables: initialize registers in nft_do_chain()") had to add a unconditional memset to the nftables register space to avoid leaking stack information to userspace.
This memset shows up in benchmarks. After this change, this commit can be reverted again.
Note that this breaks userspace compatibility, because theoretically you can do
rule 1: reg2 := meta load iif, reg2 == 1 jump ... rule 2: reg2 == 2 jump ... // read access with no store in this rule
... after this change this is rejected.
Neither nftables nor iptables-nft generate such rules, each rule is always standalone.
This resuts in a small increase of nft_ctx structure by sizeof(long).
To cope with hypothetical rulesets like the example above one could emit on-demand "reg[x] = 0" store when generating the datapath blob in nf_tables_commit_chain_prepare().
A patch that does this is linked to below.
For now, lets disable this. In nf_tables, a rule is the smallest unit that can be replaced from userspace, i.e. a hypothetical ruleset that relies on earlier initialisations of registers can't be changed at will as register usage would need to be coordinated.
Link: https://lore.kernel.org/netfilter-devel/20240627135330.17039-4-fw@strlen.de/ Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Pablo Neira Ayuso pablo@netfilter.org Stable-dep-of: a67fd55f6a09 ("netfilter: nf_tables: remove redundant chain validation on register store") Signed-off-by: Sasha Levin sashal@kernel.org --- include/net/netfilter/nf_tables.h | 1 + net/netfilter/nf_tables_api.c | 38 +++++++++++++++++++++++++++---- 2 files changed, 35 insertions(+), 4 deletions(-)
diff --git a/include/net/netfilter/nf_tables.h b/include/net/netfilter/nf_tables.h index 917edb4380e58..a8fcbdb37a7f9 100644 --- a/include/net/netfilter/nf_tables.h +++ b/include/net/netfilter/nf_tables.h @@ -221,6 +221,7 @@ struct nft_ctx { u8 family; u8 level; bool report; + DECLARE_BITMAP(reg_inited, NFT_REG32_NUM); };
enum nft_data_desc_flags { diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 7bccfb1a8a725..8b8895e4372d9 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -146,6 +146,8 @@ static void nft_ctx_init(struct nft_ctx *ctx, ctx->report = nlmsg_report(nlh); ctx->flags = nlh->nlmsg_flags; ctx->seq = nlh->nlmsg_seq; + + bitmap_zero(ctx->reg_inited, NFT_REG32_NUM); }
static struct nft_trans *nft_trans_alloc_gfp(const struct nft_ctx *ctx, @@ -10915,8 +10917,8 @@ static int nft_validate_register_load(enum nft_registers reg, unsigned int len) int nft_parse_register_load(const struct nft_ctx *ctx, const struct nlattr *attr, u8 *sreg, u32 len) { - u32 reg; - int err; + int err, invalid_reg; + u32 reg, next_register;
err = nft_parse_register(attr, ®); if (err < 0) @@ -10926,11 +10928,36 @@ int nft_parse_register_load(const struct nft_ctx *ctx, if (err < 0) return err;
+ next_register = DIV_ROUND_UP(len, NFT_REG32_SIZE) + reg; + + /* Can't happen: nft_validate_register_load() should have failed */ + if (WARN_ON_ONCE(next_register > NFT_REG32_NUM)) + return -EINVAL; + + /* find first register that did not see an earlier store. */ + invalid_reg = find_next_zero_bit(ctx->reg_inited, NFT_REG32_NUM, reg); + + /* invalid register within the range that we're loading from? */ + if (invalid_reg < next_register) + return -ENODATA; + *sreg = reg; return 0; } EXPORT_SYMBOL_GPL(nft_parse_register_load);
+static void nft_saw_register_store(const struct nft_ctx *__ctx, + int reg, unsigned int len) +{ + unsigned int registers = DIV_ROUND_UP(len, NFT_REG32_SIZE); + struct nft_ctx *ctx = (struct nft_ctx *)__ctx; + + if (WARN_ON_ONCE(len == 0 || reg < 0)) + return; + + bitmap_set(ctx->reg_inited, reg, registers); +} + static int nft_validate_register_store(const struct nft_ctx *ctx, enum nft_registers reg, const struct nft_data *data, @@ -10952,7 +10979,7 @@ static int nft_validate_register_store(const struct nft_ctx *ctx, return err; }
- return 0; + break; default: if (type != NFT_DATA_VALUE) return -EINVAL; @@ -10965,8 +10992,11 @@ static int nft_validate_register_store(const struct nft_ctx *ctx, sizeof_field(struct nft_regs, data)) return -ERANGE;
- return 0; + break; } + + nft_saw_register_store(ctx, reg, len); + return 0; }
int nft_parse_register_store(const struct nft_ctx *ctx,