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: 2fe99eb0ccf2 ("bpf: Add x86-64 JIT support for PROBE_MEM32 pseudo instructions.")
Reported-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>
Acked-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
kernel/bpf/verifier.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 63749ad5ac6b..1dd3b99d1bb9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -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));
--
2.40.1
