[PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Daniel Borkmann]

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@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 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

[PATCH bpf-next v3 2/6] bpf: Improve check_raw_mode_ok test for MEM_UNINIT-tagged types

[Daniel Borkmann]

When checking malformed helper function signatures, also take other argument
types into account aside from just ARG_PTR_TO_UNINIT_MEM.

This concerns (formerly) ARG_PTR_TO_{INT,LONG} given uninitialized memory can
be passed there, too.

The func proto sanity check goes back to commit 435faee1aae9 ("bpf, verifier:
add ARG_PTR_TO_RAW_STACK type"), and its purpose was to detect wrong func protos
which had more than just one MEM_UNINIT-tagged type as arguments.

The reason more than one is currently not supported is as we mark stack slots with
STACK_MISC in check_helper_call() in case of raw mode based on meta.access_size to
allow uninitialized stack memory to be passed to helpers when they just write into
the buffer.

Probing for base type as well as MEM_UNINIT tagging ensures that other types do not
get missed (as it used to be the case for ARG_PTR_TO_{INT,LONG}).

Fixes: 57c3bb725a3d ("bpf: Introduce ARG_PTR_TO_{INT,LONG} arg types")
Reported-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 v1 -> v2:
 - new patch (Shung-Hsi)
 v2 -> v3:
 - base_type(type) was needed also

 kernel/bpf/verifier.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index efd9c453399e..26240637c863 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -8296,6 +8296,12 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type)
 	       type == ARG_CONST_SIZE_OR_ZERO;
 }
 
+static bool arg_type_is_raw_mem(enum bpf_arg_type type)
+{
+	return base_type(type) == ARG_PTR_TO_MEM &&
+	       type & MEM_UNINIT;
+}
+
 static bool arg_type_is_release(enum bpf_arg_type type)
 {
 	return type & OBJ_RELEASE;
@@ -9348,15 +9354,15 @@ static bool check_raw_mode_ok(const struct bpf_func_proto *fn)
 {
 	int count = 0;
 
-	if (fn->arg1_type == ARG_PTR_TO_UNINIT_MEM)
+	if (arg_type_is_raw_mem(fn->arg1_type))
 		count++;
-	if (fn->arg2_type == ARG_PTR_TO_UNINIT_MEM)
+	if (arg_type_is_raw_mem(fn->arg2_type))
 		count++;
-	if (fn->arg3_type == ARG_PTR_TO_UNINIT_MEM)
+	if (arg_type_is_raw_mem(fn->arg3_type))
 		count++;
-	if (fn->arg4_type == ARG_PTR_TO_UNINIT_MEM)
+	if (arg_type_is_raw_mem(fn->arg4_type))
 		count++;
-	if (fn->arg5_type == ARG_PTR_TO_UNINIT_MEM)
+	if (arg_type_is_raw_mem(fn->arg5_type))
 		count++;
 
 	/* We only support one arg being in raw mode at the moment,
-- 
2.43.0

[PATCH bpf-next v3 3/6] bpf: Zero former ARG_PTR_TO_{LONG,INT} args in case of error

[Daniel Borkmann]

For all non-tracing helpers which formerly had ARG_PTR_TO_{LONG,INT} as input
arguments, zero the value for the case of an error as otherwise it could leak
memory. For tracing, it is not needed given CAP_PERFMON can already read all
kernel memory anyway hence bpf_get_func_arg() and bpf_get_func_ret() is skipped
in here.

Also, rearrange the MTU checker helpers a bit to among other nit fixes
consolidate flag checks such that we only need to zero in one location with
regards to malformed flag inputs.

Fixes: 8a67f2de9b1d ("bpf: expose bpf_strtol and bpf_strtoul to all program types")
Fixes: d7a4cb9b6705 ("bpf: Introduce bpf_strtol and bpf_strtoul helpers")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 v1 -> v2:
 - only set *mtu_len in error path (Alexei)

 kernel/bpf/helpers.c |  2 ++
 kernel/bpf/syscall.c |  1 +
 net/core/filter.c    | 35 +++++++++++++++++------------------
 3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index d2c8945e8297..c0620bad5dc8 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -523,6 +523,7 @@ BPF_CALL_4(bpf_strtol, const char *, buf, size_t, buf_len, u64, flags,
 	long long _res;
 	int err;
 
+	*res = 0;
 	err = __bpf_strtoll(buf, buf_len, flags, &_res);
 	if (err < 0)
 		return err;
@@ -551,6 +552,7 @@ BPF_CALL_4(bpf_strtoul, const char *, buf, size_t, buf_len, u64, flags,
 	bool is_negative;
 	int err;
 
+	*res = 0;
 	err = __bpf_strtoull(buf, buf_len, flags, &_res, &is_negative);
 	if (err < 0)
 		return err;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index feb276771c03..513b4301a0af 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -5934,6 +5934,7 @@ static const struct bpf_func_proto bpf_sys_close_proto = {
 
 BPF_CALL_4(bpf_kallsyms_lookup_name, const char *, name, int, name_sz, int, flags, u64 *, res)
 {
+	*res = 0;
 	if (flags)
 		return -EINVAL;
 
diff --git a/net/core/filter.c b/net/core/filter.c
index 4be175f84eb9..c219385e7bb4 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -6264,18 +6264,19 @@ BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb,
 	int skb_len, dev_len;
 	int mtu;
 
-	if (unlikely(flags & ~(BPF_MTU_CHK_SEGS)))
-		return -EINVAL;
-
-	if (unlikely(flags & BPF_MTU_CHK_SEGS && (len_diff || *mtu_len)))
+	if (unlikely((flags & ~(BPF_MTU_CHK_SEGS)) ||
+		     (flags & BPF_MTU_CHK_SEGS && (len_diff || *mtu_len)))) {
+		*mtu_len = 0;
 		return -EINVAL;
+	}
 
 	dev = __dev_via_ifindex(dev, ifindex);
-	if (unlikely(!dev))
+	if (unlikely(!dev)) {
+		*mtu_len = 0;
 		return -ENODEV;
+	}
 
 	mtu = READ_ONCE(dev->mtu);
-
 	dev_len = mtu + dev->hard_header_len;
 
 	/* If set use *mtu_len as input, L3 as iph->tot_len (like fib_lookup) */
@@ -6286,10 +6287,10 @@ BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb,
 		ret = BPF_MTU_CHK_RET_SUCCESS;
 		goto out;
 	}
-	/* At this point, skb->len exceed MTU, but as it include length of all
-	 * segments, it can still be below MTU.  The SKB can possibly get
-	 * re-segmented in transmit path (see validate_xmit_skb).  Thus, user
-	 * must choose if segs are to be MTU checked.
+	/* At this point, skb->len exceeds MTU, but as it includes the length
+	 * of all segments, it can still be below MTU. The skb can possibly
+	 * get re-segmented in transmit path (see validate_xmit_skb). Thus,
+	 * the user must choose if segments are to be MTU checked.
 	 */
 	if (skb_is_gso(skb)) {
 		ret = BPF_MTU_CHK_RET_SUCCESS;
@@ -6299,9 +6300,7 @@ BPF_CALL_5(bpf_skb_check_mtu, struct sk_buff *, skb,
 			ret = BPF_MTU_CHK_RET_SEGS_TOOBIG;
 	}
 out:
-	/* BPF verifier guarantees valid pointer */
 	*mtu_len = mtu;
-
 	return ret;
 }
 
@@ -6314,16 +6313,18 @@ BPF_CALL_5(bpf_xdp_check_mtu, struct xdp_buff *, xdp,
 	int mtu, dev_len;
 
 	/* XDP variant doesn't support multi-buffer segment check (yet) */
-	if (unlikely(flags))
+	if (unlikely(flags)) {
+		*mtu_len = 0;
 		return -EINVAL;
+	}
 
 	dev = __dev_via_ifindex(dev, ifindex);
-	if (unlikely(!dev))
+	if (unlikely(!dev)) {
+		*mtu_len = 0;
 		return -ENODEV;
+	}
 
 	mtu = READ_ONCE(dev->mtu);
-
-	/* Add L2-header as dev MTU is L3 size */
 	dev_len = mtu + dev->hard_header_len;
 
 	/* Use *mtu_len as input, L3 as iph->tot_len (like fib_lookup) */
@@ -6334,9 +6335,7 @@ BPF_CALL_5(bpf_xdp_check_mtu, struct xdp_buff *, xdp,
 	if (xdp_len > dev_len)
 		ret = BPF_MTU_CHK_RET_FRAG_NEEDED;
 
-	/* BPF verifier guarantees valid pointer */
 	*mtu_len = mtu;
-
 	return ret;
 }
 
-- 
2.43.0

[PATCH bpf-next v3 4/6] selftests/bpf: Fix ARG_PTR_TO_LONG {half-,}uninitialized test

[Daniel Borkmann]

The assumption of 'in privileged mode reads from uninitialized stack locations
are permitted' is not quite correct since the verifier was probing for read
access rather than write access. Both tests need to be annotated as __success
for privileged and unprivileged.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 tools/testing/selftests/bpf/progs/verifier_int_ptr.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
index 9fc3fae5cd83..87206803c025 100644
--- a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
+++ b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
@@ -8,7 +8,6 @@
 SEC("socket")
 __description("ARG_PTR_TO_LONG uninitialized")
 __success
-__failure_unpriv __msg_unpriv("invalid indirect read from stack R4 off -16+0 size 8")
 __naked void arg_ptr_to_long_uninitialized(void)
 {
 	asm volatile ("					\
@@ -36,9 +35,7 @@ __naked void arg_ptr_to_long_uninitialized(void)
 
 SEC("socket")
 __description("ARG_PTR_TO_LONG half-uninitialized")
-/* in privileged mode reads from uninitialized stack locations are permitted */
-__success __failure_unpriv
-__msg_unpriv("invalid indirect read from stack R4 off -16+4 size 8")
+__success
 __retval(0)
 __naked void ptr_to_long_half_uninitialized(void)
 {
-- 
2.43.0

[PATCH bpf-next v3 5/6] selftests/bpf: Rename ARG_PTR_TO_LONG test description

[Daniel Borkmann]

Given we got rid of ARG_PTR_TO_LONG, change the test case description to
avoid potential confusion:

  # ./vmtest.sh -- ./test_progs -t verifier_int_ptr
  [...]
  ./test_progs -t verifier_int_ptr
  [    1.610563] bpf_testmod: loading out-of-tree module taints kernel.
  [    1.611049] bpf_testmod: module verification failed: signature and/or required key missing - tainting kernel
  #489/1   verifier_int_ptr/arg pointer to long uninitialized:OK
  #489/2   verifier_int_ptr/arg pointer to long half-uninitialized:OK
  #489/3   verifier_int_ptr/arg pointer to long misaligned:OK
  #489/4   verifier_int_ptr/arg pointer to long size < sizeof(long):OK
  #489/5   verifier_int_ptr/arg pointer to long initialized:OK
  #489     verifier_int_ptr:OK
  Summary: 1/5 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
---
 v1 -> v2:
 - new patch

 tools/testing/selftests/bpf/progs/verifier_int_ptr.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
index 87206803c025..5f2efb895edb 100644
--- a/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
+++ b/tools/testing/selftests/bpf/progs/verifier_int_ptr.c
@@ -6,7 +6,7 @@
 #include "bpf_misc.h"
 
 SEC("socket")
-__description("ARG_PTR_TO_LONG uninitialized")
+__description("arg pointer to long uninitialized")
 __success
 __naked void arg_ptr_to_long_uninitialized(void)
 {
@@ -34,7 +34,7 @@ __naked void arg_ptr_to_long_uninitialized(void)
 }
 
 SEC("socket")
-__description("ARG_PTR_TO_LONG half-uninitialized")
+__description("arg pointer to long half-uninitialized")
 __success
 __retval(0)
 __naked void ptr_to_long_half_uninitialized(void)
@@ -64,7 +64,7 @@ __naked void ptr_to_long_half_uninitialized(void)
 }
 
 SEC("cgroup/sysctl")
-__description("ARG_PTR_TO_LONG misaligned")
+__description("arg pointer to long misaligned")
 __failure __msg("misaligned stack access off 0+-20+0 size 8")
 __naked void arg_ptr_to_long_misaligned(void)
 {
@@ -95,7 +95,7 @@ __naked void arg_ptr_to_long_misaligned(void)
 }
 
 SEC("cgroup/sysctl")
-__description("ARG_PTR_TO_LONG size < sizeof(long)")
+__description("arg pointer to long size < sizeof(long)")
 __failure __msg("invalid indirect access to stack R4 off=-4 size=8")
 __naked void to_long_size_sizeof_long(void)
 {
@@ -124,7 +124,7 @@ __naked void to_long_size_sizeof_long(void)
 }
 
 SEC("cgroup/sysctl")
-__description("ARG_PTR_TO_LONG initialized")
+__description("arg pointer to long initialized")
 __success
 __naked void arg_ptr_to_long_initialized(void)
 {
-- 
2.43.0

[PATCH bpf-next v3 6/6] selftests/bpf: Add a test case to write into .rodata

[Daniel Borkmann]

Add a test case which attempts to write into .rodata section of the
BPF program, and for comparison this adds test cases also for .bss
and .data section.

Before fix:

  # ./vmtest.sh -- ./test_progs -t verifier_const
  [...]
  ./test_progs -t verifier_const
  tester_init:PASS:tester_log_buf 0 nsec
  process_subtest:PASS:obj_open_mem 0 nsec
  process_subtest:PASS:specs_alloc 0 nsec
  run_subtest:PASS:obj_open_mem 0 nsec
  run_subtest:FAIL:unexpected_load_success unexpected success: 0
  #465/1   verifier_const/rodata: write rejected:FAIL
  #465/2   verifier_const/bss: write accepted:OK
  #465/3   verifier_const/data: write accepted:OK
  #465     verifier_const:FAIL
  [...]

After fix:

  # ./vmtest.sh -- ./test_progs -t verifier_const
  [...]
  ./test_progs -t verifier_const
  #465/1   verifier_const/rodata: write rejected:OK
  #465/2   verifier_const/bss: write accepted:OK
  #465/3   verifier_const/data: write accepted:OK
  #465     verifier_const:OK
  [...]

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
---
 v1 -> v2:
 - const volatile long (Andrii)

 .../selftests/bpf/prog_tests/verifier.c       |  2 +
 .../selftests/bpf/progs/verifier_const.c      | 42 +++++++++++++++++++
 2 files changed, 44 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/progs/verifier_const.c

diff --git a/tools/testing/selftests/bpf/prog_tests/verifier.c b/tools/testing/selftests/bpf/prog_tests/verifier.c
index 80a90c627182..98d195ff778d 100644
--- a/tools/testing/selftests/bpf/prog_tests/verifier.c
+++ b/tools/testing/selftests/bpf/prog_tests/verifier.c
@@ -21,6 +21,7 @@
 #include "verifier_cgroup_inv_retcode.skel.h"
 #include "verifier_cgroup_skb.skel.h"
 #include "verifier_cgroup_storage.skel.h"
+#include "verifier_const.skel.h"
 #include "verifier_const_or.skel.h"
 #include "verifier_ctx.skel.h"
 #include "verifier_ctx_sk_msg.skel.h"
@@ -145,6 +146,7 @@ void test_verifier_cfg(void)                  { RUN(verifier_cfg); }
 void test_verifier_cgroup_inv_retcode(void)   { RUN(verifier_cgroup_inv_retcode); }
 void test_verifier_cgroup_skb(void)           { RUN(verifier_cgroup_skb); }
 void test_verifier_cgroup_storage(void)       { RUN(verifier_cgroup_storage); }
+void test_verifier_const(void)                { RUN(verifier_const); }
 void test_verifier_const_or(void)             { RUN(verifier_const_or); }
 void test_verifier_ctx(void)                  { RUN(verifier_ctx); }
 void test_verifier_ctx_sk_msg(void)           { RUN(verifier_ctx_sk_msg); }
diff --git a/tools/testing/selftests/bpf/progs/verifier_const.c b/tools/testing/selftests/bpf/progs/verifier_const.c
new file mode 100644
index 000000000000..5158dbea8c43
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/verifier_const.c
@@ -0,0 +1,42 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2024 Isovalent */
+
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include "bpf_misc.h"
+
+const volatile long foo = 42;
+long bar;
+long bart = 96;
+
+SEC("tc/ingress")
+__description("rodata: write rejected")
+__failure __msg("write into map forbidden")
+int tcx1(struct __sk_buff *skb)
+{
+	char buff[] = { '8', '4', '\0' };
+	bpf_strtol(buff, sizeof(buff), 0, (long *)&foo);
+	return TCX_PASS;
+}
+
+SEC("tc/ingress")
+__description("bss: write accepted")
+__success
+int tcx2(struct __sk_buff *skb)
+{
+	char buff[] = { '8', '4', '\0' };
+	bpf_strtol(buff, sizeof(buff), 0, &bar);
+	return TCX_PASS;
+}
+
+SEC("tc/ingress")
+__description("data: write accepted")
+__success
+int tcx3(struct __sk_buff *skb)
+{
+	char buff[] = { '8', '4', '\0' };
+	bpf_strtol(buff, sizeof(buff), 0, &bart);
+	return TCX_PASS;
+}
+
+char LICENSE[] SEC("license") = "GPL";
-- 
2.43.0

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Alexei Starovoitov]

On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> 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),

This is not correct.
ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".

> -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);

as seen here.

BPF_CALL_4(bpf_strto[u]l, ... long *, res)
are buggy.
but they call __bpf_strtoll which takes 'long long' correctly.

The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
but this patch shouldn't make the verifier see it as sizeof(long).

pw-bot: cr

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Daniel Borkmann]

On 9/5/24 9:39 PM, Alexei Starovoitov wrote:
> On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>> 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),
> 
> This is not correct.
> ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".
> 
>> -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);
> 
> as seen here.
> 
> BPF_CALL_4(bpf_strto[u]l, ... long *, res)
> are buggy.

Right, the int_ptr_type_to_size() checks mem based on u64 vs writing
long in the helper which mismatches on 32bit archs.

> but they call __bpf_strtoll which takes 'long long' correctly.
> 
> The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
> but this patch shouldn't make the verifier see it as sizeof(long).

Ok, so I'll fix the BPF_CALL signatures for the affected helpers as
one more patch and also align arg*_size to {s,u}64 then so that there's
no mismatch.

Thanks,
Daniel

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Daniel Borkmann]

On 9/5/24 10:27 PM, Daniel Borkmann wrote:
> On 9/5/24 9:39 PM, Alexei Starovoitov wrote:
>> On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>>> 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),
>>
>> This is not correct.
>> ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".
>>
>>> -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);
>>
>> as seen here.
>>
>> BPF_CALL_4(bpf_strto[u]l, ... long *, res)
>> are buggy.
> 
> Right, the int_ptr_type_to_size() checks mem based on u64 vs writing
> long in the helper which mismatches on 32bit archs.
> 
>> but they call __bpf_strtoll which takes 'long long' correctly.
>>
>> The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
>> but this patch shouldn't make the verifier see it as sizeof(long).
> 
> Ok, so I'll fix the BPF_CALL signatures for the affected helpers as
> one more patch and also align arg*_size to {s,u}64 then so that there's
> no mismatch.

Not fixing up BPF_CALL signatures but aligning .arg*_size to sizeof(u64)
would fwiw keep things as today. This has the downside that on 32bit archs
one could end up leaking out 4b of uninit mem (as verifier assumes fixed
64bit and in case of write there is no need to init the var as verifier
thinks the helper will fill it all). Ugly bit is the func proto is enabled
in bpf_base_func_proto() which is ofc available for unpriv (if someone
actually has it turned on..).

Fixing up BPF_CALL signatures for bpf_strto{u,}l where res pointer becomes
{s,u}64 and .arg*_size fixed 8b, would be nicer, but assuming this includes
also the uapi helper description, then we'll also have to end up adapting
selftests (given compiler warns on ptr type mismatch) :/

One option could be we fix up BPF_CALL sites, but not the uapi helper such
that selftests stay as they are. For 64bit no change, but 32bit archs this
will be subtle as we write beyond the passed/expected long inside the helper.

Last option is to have it like in this patch to reflect actual long in
.arg*_size still no change 64bit and 32bit becomes also correct, just
quirk that it's not fixed/portable size. Thoughts on the options? All ugly,
but last one looked most sane to me fwiw.

Thanks,
Daniel

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Daniel Borkmann]

On 9/6/24 12:56 AM, Daniel Borkmann wrote:
> On 9/5/24 10:27 PM, Daniel Borkmann wrote:
>> On 9/5/24 9:39 PM, Alexei Starovoitov wrote:
>>> On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>>>> 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),
>>>
>>> This is not correct.
>>> ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".
>>>
>>>> -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);
>>>
>>> as seen here.
>>>
>>> BPF_CALL_4(bpf_strto[u]l, ... long *, res)
>>> are buggy.
>>
>> Right, the int_ptr_type_to_size() checks mem based on u64 vs writing
>> long in the helper which mismatches on 32bit archs.
>>
>>> but they call __bpf_strtoll which takes 'long long' correctly.
>>>
>>> The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
>>> but this patch shouldn't make the verifier see it as sizeof(long).
>>
>> Ok, so I'll fix the BPF_CALL signatures for the affected helpers as
>> one more patch and also align arg*_size to {s,u}64 then so that there's
>> no mismatch.
> 
> Not fixing up BPF_CALL signatures but aligning .arg*_size to sizeof(u64)
> would fwiw keep things as today. This has the downside that on 32bit archs
> one could end up leaking out 4b of uninit mem (as verifier assumes fixed
> 64bit and in case of write there is no need to init the var as verifier
> thinks the helper will fill it all). Ugly bit is the func proto is enabled
> in bpf_base_func_proto() which is ofc available for unpriv (if someone
> actually has it turned on..).
> 
> Fixing up BPF_CALL signatures for bpf_strto{u,}l where res pointer becomes
> {s,u}64 and .arg*_size fixed 8b, would be nicer, but assuming this includes
> also the uapi helper description, then we'll also have to end up adapting
> selftests (given compiler warns on ptr type mismatch) :/
> 
> One option could be we fix up BPF_CALL sites, but not the uapi helper such
> that selftests stay as they are. For 64bit no change, but 32bit archs this
> will be subtle as we write beyond the passed/expected long inside the helper.

Nevermind, scratch the incorrect last part, only this option would do the
trick since from bpf pov its bpf-side "long" (as its unchanged in the uapi
header which gets pulled into the prog).

Thanks,
Daniel

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Alexei Starovoitov]

On Thu, Sep 5, 2024 at 4:14 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 9/6/24 12:56 AM, Daniel Borkmann wrote:
> > On 9/5/24 10:27 PM, Daniel Borkmann wrote:
> >> On 9/5/24 9:39 PM, Alexei Starovoitov wrote:
> >>> On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
> >>>> 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),
> >>>
> >>> This is not correct.
> >>> ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".
> >>>
> >>>> -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);
> >>>
> >>> as seen here.
> >>>
> >>> BPF_CALL_4(bpf_strto[u]l, ... long *, res)
> >>> are buggy.
> >>
> >> Right, the int_ptr_type_to_size() checks mem based on u64 vs writing
> >> long in the helper which mismatches on 32bit archs.
> >>
> >>> but they call __bpf_strtoll which takes 'long long' correctly.
> >>>
> >>> The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
> >>> but this patch shouldn't make the verifier see it as sizeof(long).
> >>
> >> Ok, so I'll fix the BPF_CALL signatures for the affected helpers as
> >> one more patch and also align arg*_size to {s,u}64 then so that there's
> >> no mismatch.
> >
> > Not fixing up BPF_CALL signatures but aligning .arg*_size to sizeof(u64)
> > would fwiw keep things as today. This has the downside that on 32bit archs
> > one could end up leaking out 4b of uninit mem (as verifier assumes fixed
> > 64bit and in case of write there is no need to init the var as verifier
> > thinks the helper will fill it all). Ugly bit is the func proto is enabled
> > in bpf_base_func_proto() which is ofc available for unpriv (if someone
> > actually has it turned on..).
> >
> > Fixing up BPF_CALL signatures for bpf_strto{u,}l where res pointer becomes
> > {s,u}64 and .arg*_size fixed 8b, would be nicer, but assuming this includes
> > also the uapi helper description, then we'll also have to end up adapting
> > selftests (given compiler warns on ptr type mismatch) :/
> >
> > One option could be we fix up BPF_CALL sites, but not the uapi helper such
> > that selftests stay as they are. For 64bit no change, but 32bit archs this
> > will be subtle as we write beyond the passed/expected long inside the helper.
>
> Nevermind, scratch the incorrect last part, only this option would do the
> trick since from bpf pov its bpf-side "long" (as its unchanged in the uapi
> header which gets pulled into the prog).

Right. From bpf side 'long *' is ok-sh and it's ok to stay this way
in uapi/bpf.h and from there in bpf_helper_defs.h,
but BPF_CALL(bpf_strol..) needs to change.
And if we fix that we should probably change uapi/bpf.h to stay consistent.
Maybe we should use 'u64 *' everywhere then?

On 32-bit archs bpf_strtol helpers were broken,
since they were converting string to 'long long', but assigning
result into 32-bit 'long *',
so upper bits will be seen as uninited from bpf prog pov.
This series are fixing the error path of uninit, but looks like
non-error path was broken on 32-bit archs too.

Thankfully bpf_strto[u]l are the only helpers that take 'long *'.
Other helpers use 'u64 *' in similar situations.

Re: [PATCH bpf-next v3 1/6] bpf: Fix helper writes to read-only maps

[Daniel Borkmann]

On 9/6/24 2:15 AM, Alexei Starovoitov wrote:
> On Thu, Sep 5, 2024 at 4:14 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>> On 9/6/24 12:56 AM, Daniel Borkmann wrote:
>>> On 9/5/24 10:27 PM, Daniel Borkmann wrote:
>>>> On 9/5/24 9:39 PM, Alexei Starovoitov wrote:
>>>>> On Thu, Sep 5, 2024 at 6:48 AM Daniel Borkmann <daniel@iogearbox.net> wrote:
>>>>>> 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),
>>>>>
>>>>> This is not correct.
>>>>> ARG_PTR_TO_LONG is bpf-side "long", not kernel side "long".
>>>>>
>>>>>> -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);
>>>>>
>>>>> as seen here.
>>>>>
>>>>> BPF_CALL_4(bpf_strto[u]l, ... long *, res)
>>>>> are buggy.
>>>>
>>>> Right, the int_ptr_type_to_size() checks mem based on u64 vs writing
>>>> long in the helper which mismatches on 32bit archs.
>>>>
>>>>> but they call __bpf_strtoll which takes 'long long' correctly.
>>>>>
>>>>> The fix for BPF_CALL_4(bpf_strto[u]l and uapi/bpf.h is orthogonal,
>>>>> but this patch shouldn't make the verifier see it as sizeof(long).
>>>>
>>>> Ok, so I'll fix the BPF_CALL signatures for the affected helpers as
>>>> one more patch and also align arg*_size to {s,u}64 then so that there's
>>>> no mismatch.
>>>
>>> Not fixing up BPF_CALL signatures but aligning .arg*_size to sizeof(u64)
>>> would fwiw keep things as today. This has the downside that on 32bit archs
>>> one could end up leaking out 4b of uninit mem (as verifier assumes fixed
>>> 64bit and in case of write there is no need to init the var as verifier
>>> thinks the helper will fill it all). Ugly bit is the func proto is enabled
>>> in bpf_base_func_proto() which is ofc available for unpriv (if someone
>>> actually has it turned on..).
>>>
>>> Fixing up BPF_CALL signatures for bpf_strto{u,}l where res pointer becomes
>>> {s,u}64 and .arg*_size fixed 8b, would be nicer, but assuming this includes
>>> also the uapi helper description, then we'll also have to end up adapting
>>> selftests (given compiler warns on ptr type mismatch) :/
>>>
>>> One option could be we fix up BPF_CALL sites, but not the uapi helper such
>>> that selftests stay as they are. For 64bit no change, but 32bit archs this
>>> will be subtle as we write beyond the passed/expected long inside the helper.
>>
>> Nevermind, scratch the incorrect last part, only this option would do the
>> trick since from bpf pov its bpf-side "long" (as its unchanged in the uapi
>> header which gets pulled into the prog).
> 
> Right. From bpf side 'long *' is ok-sh and it's ok to stay this way
> in uapi/bpf.h and from there in bpf_helper_defs.h,
> but BPF_CALL(bpf_strol..) needs to change.
> And if we fix that we should probably change uapi/bpf.h to stay consistent.
> Maybe we should use 'u64 *' everywhere then?

I'd love to also change uapi/bpf.h, just that this needs changes in existing
BPF selftests as otherwise the build errors out e.g. on regular x86-64 with
the following (without the -Werror this is 'just' a warning):

   [...]
   progs/verifier_const.c:28:36: error: incompatible pointer types passing 'long *' to parameter of type '__s64 *' (aka 'long long *') [-Werror,-Wincompatible-pointer-types]
      28 |         bpf_strtol(buff, sizeof(buff), 0, &bar);
         |                                           ^~~~
   [...]

One could argue that these two helpers are still fairly niche, but otoh,
they've been around since 2019. :/ So I guess it's probably better to stay
with the uapi/bpf.h inconsistency that they remain at {unsigned,} long
instead of __{u,s}64 such that user code does not need to be adapted to the
signature change.

> On 32-bit archs bpf_strtol helpers were broken,
> since they were converting string to 'long long', but assigning
> result into 32-bit 'long *',
> so upper bits will be seen as uninited from bpf prog pov.
> This series are fixing the error path of uninit, but looks like
> non-error path was broken on 32-bit archs too.
> 
> Thankfully bpf_strto[u]l are the only helpers that take 'long *'.
> Other helpers use 'u64 *' in similar situations.

Agree, thankfully just those which slipped through..