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Subject[PATCH bpf-next] bpf: determine buf_info inside check_buffer_access()
Instead of determining buf_info string in the caller of
check_buffer_access(), we can determine whether the register type is read-only
through type_is_rdonly_mem() helper inside check_buffer_access() and construct
buf_info, making the code slightly cleaner.

Signed-off-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---

Initially I tried to remove the buf_info argument from
__check_buffer_access(), however check_tp_buffer_access() uses "tracepoint"
(rather than the usual "rdonly"/"rdwr") as it's buf_info, thus I decide to
leave __check_buffer_access() as-is, and only change check_buffer_access()
instead.

kernel/bpf/verifier.c | 12 +++---------
1 file changed, 3 insertions(+), 9 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a39eedecc93a..518238029e46 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4047,9 +4047,9 @@ static int check_buffer_access(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int regno, int off, int size,
bool zero_size_allowed,
- const char *buf_info,
u32 *max_access)
{
+ const char *buf_info = type_is_rdonly_mem(reg->type) ? "rdonly" : "rdwr";
int err;

err = __check_buffer_access(env, buf_info, reg, regno, off, size);
@@ -4543,7 +4543,6 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
value_regno);
} else if (base_type(reg->type) == PTR_TO_BUF) {
bool rdonly_mem = type_is_rdonly_mem(reg->type);
- const char *buf_info;
u32 *max_access;

if (rdonly_mem) {
@@ -4552,15 +4551,13 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
regno, reg_type_str(env, reg->type));
return -EACCES;
}
- buf_info = "rdonly";
max_access = &env->prog->aux->max_rdonly_access;
} else {
- buf_info = "rdwr";
max_access = &env->prog->aux->max_rdwr_access;
}

err = check_buffer_access(env, reg, regno, off, size, false,
- buf_info, max_access);
+ max_access);

if (!err && value_regno >= 0 && (rdonly_mem || t == BPF_READ))
mark_reg_unknown(env, regs, value_regno);
@@ -4823,7 +4820,6 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
struct bpf_call_arg_meta *meta)
{
struct bpf_reg_state *regs = cur_regs(env), *reg = &regs[regno];
- const char *buf_info;
u32 *max_access;

switch (base_type(reg->type)) {
@@ -4850,15 +4846,13 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
if (meta && meta->raw_mode)
return -EACCES;

- buf_info = "rdonly";
max_access = &env->prog->aux->max_rdonly_access;
} else {
- buf_info = "rdwr";
max_access = &env->prog->aux->max_rdwr_access;
}
return check_buffer_access(env, reg, regno, reg->off,
access_size, zero_size_allowed,
- buf_info, max_access);
+ max_access);
case PTR_TO_STACK:
return check_stack_range_initialized(
env,
--
2.35.1
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