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bpf: Temporarily disable atomic operations in BPF arena 

Currently, the x86 JIT handling PROBE_MEM32 tagged accesses is not
equipped to handle atomic accesses into PTR_TO_ARENA, as no PROBE_MEM32
tagging is performed and no handling is enabled for them.

This will lead to unsafety as the offset into arena will dereferenced
directly without turning it into a base + offset access into the arena
region.

Since the changes to the x86 JIT will be fairly involved, for now,
temporarily disallow use of PTR_TO_ARENA as the destination operand for
atomics until support is added to the JIT backend.

Fixes: 2fe99eb0cc ("bpf: Add x86-64 JIT support for PROBE_MEM32 pseudo instructions.")
Reported-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Acked-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Message-ID: <20240314174931.98702-1-puranjay12@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2024-03-14 17:49:31 +00:00 committed by Alexei Starovoitov
parent e30cef001d
commit 44d79142ed
1 changed files with 9 additions and 1 deletions
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10
kernel/bpf/verifier.c
View File

@ -5682,6 +5682,13 @@ static bool is_flow_key_reg(struct bpf_verifier_env *env, int regno)
return reg->type == PTR_TO_FLOW_KEYS;
}
static bool is_arena_reg(struct bpf_verifier_env *env, int regno)
{
const struct bpf_reg_state *reg = reg_state(env, regno);
return reg->type == PTR_TO_ARENA;
}
static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
#ifdef CONFIG_NET
[PTR_TO_SOCKET] = &btf_sock_ids[BTF_SOCK_TYPE_SOCK],
@ -7019,7 +7026,8 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
if (is_ctx_reg(env, insn->dst_reg) ||
is_pkt_reg(env, insn->dst_reg) ||
is_flow_key_reg(env, insn->dst_reg) ||
is_sk_reg(env, insn->dst_reg)) {
is_sk_reg(env, insn->dst_reg) ||
is_arena_reg(env, insn->dst_reg)) {
verbose(env, "BPF_ATOMIC stores into R%d %s is not allowed\n",
insn->dst_reg,
reg_type_str(env, reg_state(env, insn->dst_reg)->type));