Lonial found an issue that despite user- and BPF-side frozen BPF map
(like in case of .rodata), it was still possible to write into it from
a BPF program side through specific helpers having ARG_PTR_TO_{LONG,INT}
as arguments.
In check_func_arg() when the argument is as mentioned, the meta->raw_mode
is never set. Later, check_helper_mem_access(), under the case of
PTR_TO_MAP_VALUE as register base type, it assumes BPF_READ for the
subsequent call to check_map_access_type() and given the BPF map is
read-only it succeeds.
The helpers really need to be annotated as ARG_PTR_TO_{LONG,INT} | MEM_UNINIT
when results are written into them as opposed to read out of them. The
latter indicates that it's okay to pass a pointer to uninitialized memory
as the memory is written to anyway.
However, ARG_PTR_TO_{LONG,INT} is a special case of ARG_PTR_TO_FIXED_SIZE_MEM
just with additional alignment requirement. So it is better to just get
rid of the ARG_PTR_TO_{LONG,INT} special cases altogether and reuse the
fixed size memory types. For this, add MEM_ALIGNED to additionally ensure
alignment given these helpers write directly into the args via *<ptr> = val.
The .arg*_size has been initialized reflecting the actual sizeof(*<ptr>).
In some of the helpers these are long types, in others these are fixed
integer types.
MEM_ALIGNED can only be used in combination with MEM_FIXED_SIZE annotated
argument types, since in !MEM_FIXED_SIZE cases the verifier does not know
the buffer size a priori and therefore cannot blindly write *<ptr> = val.
Fixes: 57c3bb725a3d ("bpf: Introduce ARG_PTR_TO_{INT,LONG} arg types")
Reported-by: Lonial Con <kongln9170@xxxxxxxxx>
Signed-off-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
---
v1 -> v2:
- const volatile long (Andrii)
include/linux/bpf.h | 7 +++++--
kernel/bpf/helpers.c | 8 ++++++--
kernel/bpf/syscall.c | 4 +++-
kernel/bpf/verifier.c | 38 +++++---------------------------------
kernel/trace/bpf_trace.c | 8 ++++++--
net/core/filter.c | 8 ++++++--
6 files changed, 31 insertions(+), 42 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 6f87fb014fba..6a61ed4266b6 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -695,6 +695,11 @@ enum bpf_type_flag {
/* DYNPTR points to xdp_buff */
DYNPTR_TYPE_XDP = BIT(16 + BPF_BASE_TYPE_BITS),
+ /* Memory must be aligned on some architectures, used in combination with
+ * MEM_FIXED_SIZE.
+ */
+ MEM_ALIGNED = BIT(17 + BPF_BASE_TYPE_BITS),
+
__BPF_TYPE_FLAG_MAX,
__BPF_TYPE_LAST_FLAG = __BPF_TYPE_FLAG_MAX - 1,
};
@@ -732,8 +737,6 @@ enum bpf_arg_type {
ARG_ANYTHING, /* any (initialized) argument is ok */
ARG_PTR_TO_SPIN_LOCK, /* pointer to bpf_spin_lock */
ARG_PTR_TO_SOCK_COMMON, /* pointer to sock_common */
- ARG_PTR_TO_INT, /* pointer to int */
- ARG_PTR_TO_LONG, /* pointer to long */
ARG_PTR_TO_SOCKET, /* pointer to bpf_sock (fullsock) */
ARG_PTR_TO_BTF_ID, /* pointer to in-kernel struct */
ARG_PTR_TO_RINGBUF_MEM, /* pointer to dynamically reserved ringbuf memory */
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 3956be5d6440..d2c8945e8297 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -539,7 +539,9 @@ const struct bpf_func_proto bpf_strtol_proto = {
.arg1_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg2_type = ARG_CONST_SIZE,
.arg3_type = ARG_ANYTHING,
- .arg4_type = ARG_PTR_TO_LONG,
+ .arg4_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg4_size = sizeof(long),
};
BPF_CALL_4(bpf_strtoul, const char *, buf, size_t, buf_len, u64, flags,
@@ -567,7 +569,9 @@ const struct bpf_func_proto bpf_strtoul_proto = {
.arg1_type = ARG_PTR_TO_MEM | MEM_RDONLY,
.arg2_type = ARG_CONST_SIZE,
.arg3_type = ARG_ANYTHING,
- .arg4_type = ARG_PTR_TO_LONG,
+ .arg4_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg4_size = sizeof(unsigned long),
};
BPF_CALL_3(bpf_strncmp, const char *, s1, u32, s1_sz, const char *, s2)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index fc62f5c4faf9..feb276771c03 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5954,7 +5954,9 @@ static const struct bpf_func_proto bpf_kallsyms_lookup_name_proto = {
.arg1_type = ARG_PTR_TO_MEM,
.arg2_type = ARG_CONST_SIZE_OR_ZERO,
.arg3_type = ARG_ANYTHING,
- .arg4_type = ARG_PTR_TO_LONG,
+ .arg4_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg4_size = sizeof(u64),
};
static const struct bpf_func_proto *
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 217eb0eafa2a..efd9c453399e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8306,16 +8306,6 @@ static bool arg_type_is_dynptr(enum bpf_arg_type type)
return base_type(type) == ARG_PTR_TO_DYNPTR;
}
-static int int_ptr_type_to_size(enum bpf_arg_type type)
-{
- if (type == ARG_PTR_TO_INT)
- return sizeof(u32);
- else if (type == ARG_PTR_TO_LONG)
- return sizeof(u64);
-
- return -EINVAL;
-}
-
static int resolve_map_arg_type(struct bpf_verifier_env *env,
const struct bpf_call_arg_meta *meta,
enum bpf_arg_type *arg_type)
@@ -8388,16 +8378,6 @@ static const struct bpf_reg_types mem_types = {
},
};
-static const struct bpf_reg_types int_ptr_types = {
- .types = {
- PTR_TO_STACK,
- PTR_TO_PACKET,
- PTR_TO_PACKET_META,
- PTR_TO_MAP_KEY,
- PTR_TO_MAP_VALUE,
- },
-};
-
static const struct bpf_reg_types spin_lock_types = {
.types = {
PTR_TO_MAP_VALUE,
@@ -8458,8 +8438,6 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
[ARG_PTR_TO_SPIN_LOCK] = &spin_lock_types,
[ARG_PTR_TO_MEM] = &mem_types,
[ARG_PTR_TO_RINGBUF_MEM] = &ringbuf_mem_types,
- [ARG_PTR_TO_INT] = &int_ptr_types,
- [ARG_PTR_TO_LONG] = &int_ptr_types,
[ARG_PTR_TO_PERCPU_BTF_ID] = &percpu_btf_ptr_types,
[ARG_PTR_TO_FUNC] = &func_ptr_types,
[ARG_PTR_TO_STACK] = &stack_ptr_types,
@@ -9025,6 +9003,11 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
err = check_helper_mem_access(env, regno,
fn->arg_size[arg], false,
meta);
+ if (err)
+ return err;
+ if (arg_type & MEM_ALIGNED)
+ err = check_ptr_alignment(env, reg, 0,
+ fn->arg_size[arg], true);
}
break;
case ARG_CONST_SIZE:
@@ -9049,17 +9032,6 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
if (err)
return err;
break;
- case ARG_PTR_TO_INT:
- case ARG_PTR_TO_LONG:
- {
- int size = int_ptr_type_to_size(arg_type);
-
- err = check_helper_mem_access(env, regno, size, false, meta);
- if (err)
- return err;
- err = check_ptr_alignment(env, reg, 0, size, true);
- break;
- }
case ARG_PTR_TO_CONST_STR:
{
err = check_reg_const_str(env, reg, regno);
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index b69a39316c0c..dbf4dff33146 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1202,7 +1202,9 @@ static const struct bpf_func_proto bpf_get_func_arg_proto = {
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
- .arg3_type = ARG_PTR_TO_LONG,
+ .arg3_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg3_size = sizeof(u64),
};
BPF_CALL_2(get_func_ret, void *, ctx, u64 *, value)
@@ -1218,7 +1220,9 @@ static const struct bpf_func_proto bpf_get_func_ret_proto = {
.func = get_func_ret,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
- .arg2_type = ARG_PTR_TO_LONG,
+ .arg2_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg2_size = sizeof(u64),
};
BPF_CALL_1(get_func_arg_cnt, void *, ctx)
diff --git a/net/core/filter.c b/net/core/filter.c
index ecf2ddf633bf..4be175f84eb9 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6346,7 +6346,9 @@ static const struct bpf_func_proto bpf_skb_check_mtu_proto = {
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
- .arg3_type = ARG_PTR_TO_INT,
+ .arg3_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg3_size = sizeof(u32),
.arg4_type = ARG_ANYTHING,
.arg5_type = ARG_ANYTHING,
};
@@ -6357,7 +6359,9 @@ static const struct bpf_func_proto bpf_xdp_check_mtu_proto = {
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_ANYTHING,
- .arg3_type = ARG_PTR_TO_INT,
+ .arg3_type = ARG_PTR_TO_FIXED_SIZE_MEM |
+ MEM_UNINIT | MEM_ALIGNED,
+ .arg3_size = sizeof(u32),
.arg4_type = ARG_ANYTHING,
.arg5_type = ARG_ANYTHING,
};
--
2.43.0
