From 801c6058d14a82179a7ee17a4b532cac6fad067f Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 29 Apr 2021 15:19:37 +0000 Subject: bpf: Fix leakage of uninitialized bpf stack under speculation The current implemented mechanisms to mitigate data disclosure under speculation mainly address stack and map value oob access from the speculative domain. However, Piotr discovered that uninitialized BPF stack is not protected yet, and thus old data from the kernel stack, potentially including addresses of kernel structures, could still be extracted from that 512 bytes large window. The BPF stack is special compared to map values since it's not zero initialized for every program invocation, whereas map values /are/ zero initialized upon their initial allocation and thus cannot leak any prior data in either domain. In the non-speculative domain, the verifier ensures that every stack slot read must have a prior stack slot write by the BPF program to avoid such data leaking issue. However, this is not enough: for example, when the pointer arithmetic operation moves the stack pointer from the last valid stack offset to the first valid offset, the sanitation logic allows for any intermediate offsets during speculative execution, which could then be used to extract any restricted stack content via side-channel. Given for unprivileged stack pointer arithmetic the use of unknown but bounded scalars is generally forbidden, we can simply turn the register-based arithmetic operation into an immediate-based arithmetic operation without the need for masking. This also gives the benefit of reducing the needed instructions for the operation. Given after the work in 7fedb63a8307 ("bpf: Tighten speculative pointer arithmetic mask"), the aux->alu_limit already holds the final immediate value for the offset register with the known scalar. Thus, a simple mov of the immediate to AX register with using AX as the source for the original instruction is sufficient and possible now in this case. Reported-by: Piotr Krysiuk Signed-off-by: Daniel Borkmann Tested-by: Piotr Krysiuk Reviewed-by: Piotr Krysiuk Reviewed-by: John Fastabend Acked-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 6023a1367853..06841517ab1e 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -302,10 +302,11 @@ struct bpf_verifier_state_list { }; /* Possible states for alu_state member. */ -#define BPF_ALU_SANITIZE_SRC 1U -#define BPF_ALU_SANITIZE_DST 2U +#define BPF_ALU_SANITIZE_SRC (1U << 0) +#define BPF_ALU_SANITIZE_DST (1U << 1) #define BPF_ALU_NEG_VALUE (1U << 2) #define BPF_ALU_NON_POINTER (1U << 3) +#define BPF_ALU_IMMEDIATE (1U << 4) #define BPF_ALU_SANITIZE (BPF_ALU_SANITIZE_SRC | \ BPF_ALU_SANITIZE_DST) -- cgit From 43016d02cf6e46edfc4696452251d34bba0c0435 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Mon, 3 May 2021 13:51:15 +0200 Subject: netfilter: arptables: use pernet ops struct during unregister Like with iptables and ebtables, hook unregistration has to use the pernet ops struct, not the template. This triggered following splat: hook not found, pf 3 num 0 WARNING: CPU: 0 PID: 224 at net/netfilter/core.c:480 __nf_unregister_net_hook+0x1eb/0x610 net/netfilter/core.c:480 [..] nf_unregister_net_hook net/netfilter/core.c:502 [inline] nf_unregister_net_hooks+0x117/0x160 net/netfilter/core.c:576 arpt_unregister_table_pre_exit+0x67/0x80 net/ipv4/netfilter/arp_tables.c:1565 Fixes: f9006acc8dfe5 ("netfilter: arp_tables: pass table pointer via nf_hook_ops") Reported-by: syzbot+dcccba8a1e41a38cb9df@syzkaller.appspotmail.com Signed-off-by: Florian Westphal Signed-off-by: Pablo Neira Ayuso --- include/linux/netfilter_arp/arp_tables.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/netfilter_arp/arp_tables.h b/include/linux/netfilter_arp/arp_tables.h index 2aab9612f6ab..4f9a4b3c5892 100644 --- a/include/linux/netfilter_arp/arp_tables.h +++ b/include/linux/netfilter_arp/arp_tables.h @@ -53,8 +53,7 @@ int arpt_register_table(struct net *net, const struct xt_table *table, const struct arpt_replace *repl, const struct nf_hook_ops *ops); void arpt_unregister_table(struct net *net, const char *name); -void arpt_unregister_table_pre_exit(struct net *net, const char *name, - const struct nf_hook_ops *ops); +void arpt_unregister_table_pre_exit(struct net *net, const char *name); extern unsigned int arpt_do_table(struct sk_buff *skb, const struct nf_hook_state *state, struct xt_table *table); -- cgit