From: Davide Ornaghi <d.ornaghi97@gmail.com> stable inclusion from stable-v6.6.143 commit eb8a8124484dbc3c2b543e207da39bbccb703d31 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/15828 CVE: CVE-2026-53134 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- [ Upstream commit ab185e0c4fb82dfba6fb86f8271e06f931d9c64c ] For NFT_FIB_RESULT_OIFNAME the destination register is declared with len = IFNAMSIZ (four 32-bit registers), but on the lookup-fail, RTN_LOCAL and oif-mismatch paths nft_fib{4,6}_eval() only writes one register via "*dest = 0". The remaining three registers are left as whatever was on the stack in nft_do_chain()'s struct nft_regs, and a downstream expression that loads the register span can leak that uninitialised kernel stack to userspace. The NFTA_FIB_F_PRESENT existence check has the same shape: it is only meaningful for NFT_FIB_RESULT_OIF, yet it was accepted for any result type while the eval stores a single byte via nft_reg_store8(), leaving the rest of the declared span stale. Fix both: - replace the bare "*dest = 0" in the eval with nft_fib_store_result(), which strscpy_pad()s the whole IFNAMSIZ for OIFNAME (and is already used on the other early-return path), and - restrict NFTA_FIB_F_PRESENT to NFT_FIB_RESULT_OIF and declare its destination as a single u8, so the marked span matches the one byte the eval writes. Fixes: f6d0cbcf09c5 ("netfilter: nf_tables: add fib expression") Suggested-by: Florian Westphal <fw@strlen.de> Cc: stable@vger.kernel.org Signed-off-by: Davide Ornaghi <d.ornaghi97@gmail.com> Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org> [ kept the tree's existing `ip6_route_lookup`/`rt6_info` machinery (missing `fib6_lookup` refactor) and changed only `*dest = 0;` to `nft_fib_store_result(dest, priv, NULL)` ] Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Dong Chenchen <dongchenchen2@huawei.com> --- net/ipv4/netfilter/nft_fib_ipv4.c | 2 +- net/ipv6/netfilter/nft_fib_ipv6.c | 2 +- net/netfilter/nft_fib.c | 6 ++++++ 3 files changed, 8 insertions(+), 2 deletions(-) diff --git a/net/ipv4/netfilter/nft_fib_ipv4.c b/net/ipv4/netfilter/nft_fib_ipv4.c index ba233fdd8188..94931d52048f 100644 --- a/net/ipv4/netfilter/nft_fib_ipv4.c +++ b/net/ipv4/netfilter/nft_fib_ipv4.c @@ -122,7 +122,7 @@ void nft_fib4_eval(const struct nft_expr *expr, struct nft_regs *regs, fl4.saddr = get_saddr(iph->daddr); } - *dest = 0; + nft_fib_store_result(dest, priv, NULL); if (fib_lookup(nft_net(pkt), &fl4, &res, FIB_LOOKUP_IGNORE_LINKSTATE)) return; diff --git a/net/ipv6/netfilter/nft_fib_ipv6.c b/net/ipv6/netfilter/nft_fib_ipv6.c index a89ce0fbfe4b..da4a35c20f10 100644 --- a/net/ipv6/netfilter/nft_fib_ipv6.c +++ b/net/ipv6/netfilter/nft_fib_ipv6.c @@ -193,7 +193,7 @@ void nft_fib6_eval(const struct nft_expr *expr, struct nft_regs *regs, } } - *dest = 0; + nft_fib_store_result(dest, priv, NULL); rt = (void *)ip6_route_lookup(nft_net(pkt), &fl6, pkt->skb, lookup_flags); if (rt->dst.error) diff --git a/net/netfilter/nft_fib.c b/net/netfilter/nft_fib.c index 507b7eba9bcd..b4f49f65fc42 100644 --- a/net/netfilter/nft_fib.c +++ b/net/netfilter/nft_fib.c @@ -107,6 +107,12 @@ int nft_fib_init(const struct nft_ctx *ctx, const struct nft_expr *expr, return -EINVAL; } + if (priv->flags & NFTA_FIB_F_PRESENT) { + if (priv->result != NFT_FIB_RESULT_OIF) + return -EINVAL; + len = sizeof(u8); + } + err = nft_parse_register_store(ctx, tb[NFTA_FIB_DREG], &priv->dreg, NULL, NFT_DATA_VALUE, len); if (err < 0) -- 2.43.0