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bpf: Refactor and streamline bounds check into helper

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commit 073815b756c51ba9d8384d924c5d1c03ca3d1ae4 upstream.

Move the bounds check in adjust_ptr_min_max_vals() into a small helper named
sanitize_check_bounds() in order to simplify the former a bit.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
[fllinden@amazon.com: backport to 5.4]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Borkmann 2021-04-29 22:08:36 +00:00 committed by Greg Kroah-Hartman
parent 4158e5fea3
commit 876d1cec93
1 changed files with 37 additions and 17 deletions
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54
kernel/bpf/verifier.c
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@ -4448,6 +4448,41 @@ static int sanitize_err(struct bpf_verifier_env *env,
return -EACCES;
}
static int sanitize_check_bounds(struct bpf_verifier_env *env,
const struct bpf_insn *insn,
const struct bpf_reg_state *dst_reg)
{
u32 dst = insn->dst_reg;
/* For unprivileged we require that resulting offset must be in bounds
* in order to be able to sanitize access later on.
*/
if (env->allow_ptr_leaks)
return 0;
switch (dst_reg->type) {
case PTR_TO_STACK:
if (check_stack_access(env, dst_reg, dst_reg->off +
dst_reg->var_off.value, 1)) {
verbose(env, "R%d stack pointer arithmetic goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
}
break;
case PTR_TO_MAP_VALUE:
if (check_map_access(env, dst, dst_reg->off, 1, false)) {
verbose(env, "R%d pointer arithmetic of map value goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
}
break;
default:
break;
}
return 0;
}
/* Handles arithmetic on a pointer and a scalar: computes new min/max and var_off.
* Caller should also handle BPF_MOV case separately.
* If we return -EACCES, caller may want to try again treating pointer as a
@ -4664,23 +4699,8 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
__reg_deduce_bounds(dst_reg);
__reg_bound_offset(dst_reg);
/* For unprivileged we require that resulting offset must be in bounds
* in order to be able to sanitize access later on.
*/
if (!env->allow_ptr_leaks) {
if (dst_reg->type == PTR_TO_MAP_VALUE &&
check_map_access(env, dst, dst_reg->off, 1, false)) {
verbose(env, "R%d pointer arithmetic of map value goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
} else if (dst_reg->type == PTR_TO_STACK &&
check_stack_access(env, dst_reg, dst_reg->off +
dst_reg->var_off.value, 1)) {
verbose(env, "R%d stack pointer arithmetic goes out of range, "
"prohibited for !root\n", dst);
return -EACCES;
}
}
if (sanitize_check_bounds(env, insn, dst_reg) < 0)
return -EACCES;
return 0;
}