[PATCH 5.15.y 0/5] Backport bounds checks for bpf

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* [PATCH 5.15.y 0/5] Backport bounds checks for bpf
       [not found] <16430256912363@kroah.com>
@ 2024-04-17 23:35 ` Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
                     ` (4 more replies)
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
  2 siblings, 5 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

These backports fix CVE-2021-4204, CVE-2022-23222 for 5.15.y.

This includes a conflict resolution with 45ce4b4f9009 ("bpf: Fix crash
due to out of bounds access into reg2btf_ids.") which was cherry-picked
previously.
Link: https://lore.kernel.org/all/20220428235751.103203-11-haoluo@google.com/

They were tested on 5.15.94 to pass LTP test bpf_prog06 with no
regressions from the bpf selftests.

Daniel Borkmann (4):
  bpf: Generalize check_ctx_reg for reuse with other types
  bpf: Generally fix helper register offset check
  bpf: Fix out of bounds access for ringbuf helpers
  bpf: Fix ringbuf memory type confusion when passing to helpers

Kumar Kartikeya Dwivedi (1):
  bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support

 include/linux/bpf.h          |  9 +++-
 include/linux/bpf_verifier.h |  4 +-
 kernel/bpf/btf.c             | 93 ++++++++++++++++++++++++++++--------
 kernel/bpf/verifier.c        | 66 +++++++++++++++++--------
 4 files changed, 129 insertions(+), 43 deletions(-)

--
2.44.0.769.g3c40516874-goog


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
@ 2024-04-17 23:35   ` Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
                     ` (3 subsequent siblings)
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel,
	Kumar Kartikeya Dwivedi

From: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Allow passing PTR_TO_CTX, if the kfunc expects a matching struct type,
and punt to PTR_TO_MEM block if reg->type does not fall in one of
PTR_TO_BTF_ID or PTR_TO_SOCK* types. This will be used by future commits
to get access to XDP and TC PTR_TO_CTX, and pass various data (flags,
l4proto, netns_id, etc.) encoded in opts struct passed as pointer to
kfunc.

For PTR_TO_MEM support, arguments are currently limited to pointer to
scalar, or pointer to struct composed of scalars. This is done so that
unsafe scenarios (like passing PTR_TO_MEM where PTR_TO_BTF_ID of
in-kernel valid structure is expected, which may have pointers) are
avoided. Since the argument checking happens basd on argument register
type, it is not easy to ascertain what the expected type is. In the
future, support for PTR_TO_MEM for kfunc can be extended to serve other
usecases. The struct type whose pointer is passed in may have maximum
nesting depth of 4, all recursively composed of scalars or struct with
scalars.

Future commits will add negative tests that check whether these
restrictions imposed for kfunc arguments are duly rejected by BPF
verifier or not.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217015031.1278167-4-memxor@gmail.com
(cherry picked from commit 3363bd0cfbb80dfcd25003cd3815b0ad8b68d0ff)
[edliaw: fixed up with changes from 45ce4b4f90091 ("bpf: Fix crash due to out of bounds access into reg2btf_ids.")]
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/btf.c | 93 +++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 73 insertions(+), 20 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0c2fa93bd8d2..b02f074363dd 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5441,6 +5441,46 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 #endif
 };
 
+/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
+static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
+					const struct btf *btf,
+					const struct btf_type *t, int rec)
+{
+	const struct btf_type *member_type;
+	const struct btf_member *member;
+	u32 i;
+
+	if (!btf_type_is_struct(t))
+		return false;
+
+	for_each_member(i, t, member) {
+		const struct btf_array *array;
+
+		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
+		if (btf_type_is_struct(member_type)) {
+			if (rec >= 3) {
+				bpf_log(log, "max struct nesting depth exceeded\n");
+				return false;
+			}
+			if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
+				return false;
+			continue;
+		}
+		if (btf_type_is_array(member_type)) {
+			array = btf_type_array(member_type);
+			if (!array->nelems)
+				return false;
+			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
+			if (!btf_type_is_scalar(member_type))
+				return false;
+			continue;
+		}
+		if (!btf_type_is_scalar(member_type))
+			return false;
+	}
+	return true;
+}
+
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
@@ -5449,6 +5489,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 	enum bpf_prog_type prog_type = env->prog->type == BPF_PROG_TYPE_EXT ?
 		env->prog->aux->dst_prog->type : env->prog->type;
 	struct bpf_verifier_log *log = &env->log;
+	bool is_kfunc = btf_is_kernel(btf);
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
@@ -5501,7 +5542,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 
 		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
-		if (btf_is_kernel(btf)) {
+		if (btf_get_prog_ctx_type(log, btf, t,
+					  env->prog->type, i)) {
+			/* If function expects ctx type in BTF check that caller
+			 * is passing PTR_TO_CTX.
+			 */
+			if (reg->type != PTR_TO_CTX) {
+				bpf_log(log,
+					"arg#%d expected pointer to ctx, but got %s\n",
+					i, btf_type_str(t));
+				return -EINVAL;
+			}
+			if (check_ctx_reg(env, reg, regno))
+				return -EINVAL;
+		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) {
 			const struct btf_type *reg_ref_t;
 			const struct btf *reg_btf;
 			const char *reg_ref_tname;
@@ -5517,14 +5571,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (reg->type == PTR_TO_BTF_ID) {
 				reg_btf = reg->btf;
 				reg_ref_id = reg->btf_id;
-			} else if (reg2btf_ids[base_type(reg->type)]) {
+			} else {
 				reg_btf = btf_vmlinux;
 				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
-			} else {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d is not a pointer to btf_id\n",
-					func_name, i,
-					btf_type_str(ref_t), ref_tname, regno);
-				return -EINVAL;
 			}
 
 			reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
@@ -5540,22 +5589,24 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					reg_ref_tname);
 				return -EINVAL;
 			}
-		} else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
-			/* If function expects ctx type in BTF check that caller
-			 * is passing PTR_TO_CTX.
-			 */
-			if (reg->type != PTR_TO_CTX) {
-				bpf_log(log,
-					"arg#%d expected pointer to ctx, but got %s\n",
-					i, btf_type_str(t));
-				return -EINVAL;
-			}
-			if (check_ctx_reg(env, reg, regno))
-				return -EINVAL;
 		} else if (ptr_to_mem_ok) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;
 
+			if (is_kfunc) {
+				/* Permit pointer to mem, but only when argument
+				 * type is pointer to scalar, or struct composed
+				 * (recursively) of scalars.
+				 */
+				if (!btf_type_is_scalar(ref_t) &&
+				    !__btf_type_is_scalar_struct(log, btf, ref_t, 0)) {
+					bpf_log(log,
+						"arg#%d pointer type %s %s must point to scalar or struct with scalar\n",
+						i, btf_type_str(ref_t), ref_tname);
+					return -EINVAL;
+				}
+			}
+
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
 				bpf_log(log,
@@ -5568,6 +5619,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (check_mem_reg(env, reg, regno, type_size))
 				return -EINVAL;
 		} else {
+			bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
+				is_kfunc ? "kernel " : "", func_name, func_id);
 			return -EINVAL;
 		}
 	}
@@ -5617,7 +5670,7 @@ int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
 			      const struct btf *btf, u32 func_id,
 			      struct bpf_reg_state *regs)
 {
-	return btf_check_func_arg_match(env, btf, func_id, regs, false);
+	return btf_check_func_arg_match(env, btf, func_id, regs, true);
 }
 
 /* Convert BTF of a function into bpf_reg_state if possible
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y 2/5] bpf: Generalize check_ctx_reg for reuse with other types
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
@ 2024-04-17 23:35   ` Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 3/5] bpf: Generally fix helper register offset check Edward Liaw
                     ` (2 subsequent siblings)
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Generalize the check_ctx_reg() helper function into a more generic named one
so that it can be reused for other register types as well to check whether
their offset is non-zero. No functional change.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf_verifier.h |  4 ++--
 kernel/bpf/btf.c             |  2 +-
 kernel/bpf/verifier.c        | 21 +++++++++++----------
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 3d04b48e502d..c0993b079ab5 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -541,8 +541,8 @@ bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
 void
 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno);
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
 
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index b02f074363dd..2f6dc3fd06bb 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5553,7 +5553,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					i, btf_type_str(t));
 				return -EINVAL;
 			}
-			if (check_ctx_reg(env, reg, regno))
+			if (check_ptr_off_reg(env, reg, regno))
 				return -EINVAL;
 		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[reg->type])) {
 			const struct btf_type *reg_ref_t;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1c95d97e7aa5..61b8a9c69b1c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3792,16 +3792,16 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno)
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
 {
-	/* Access to ctx or passing it to a helper is only allowed in
-	 * its original, unmodified form.
+	/* Access to this pointer-typed register or passing it to a helper
+	 * is only allowed in its original, unmodified form.
 	 */
 
 	if (reg->off) {
-		verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
-			regno, reg->off);
+		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
 	}
 
@@ -3809,7 +3809,8 @@ int check_ctx_reg(struct bpf_verifier_env *env,
 		char tn_buf[48];
 
 		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-		verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
+		verbose(env, "variable %s access var_off=%s disallowed\n",
+			reg_type_str(env, reg->type), tn_buf);
 		return -EACCES;
 	}
 
@@ -4260,7 +4261,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 			return -EACCES;
 		}
 
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 
@@ -5140,7 +5141,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		return err;
 
 	if (type == PTR_TO_CTX) {
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 	}
@@ -9348,7 +9349,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			return err;
 	}
 
-	err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
+	err = check_ptr_off_reg(env, &regs[ctx_reg], ctx_reg);
 	if (err < 0)
 		return err;
 
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y 3/5] bpf: Generally fix helper register offset check
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
@ 2024-04-17 23:35   ` Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Right now the assertion on check_ptr_off_reg() is only enforced for register
types PTR_TO_CTX (and open coded also for PTR_TO_BTF_ID), however, this is
insufficient since many other PTR_TO_* register types such as PTR_TO_FUNC do
not handle/expect register offsets when passed to helper functions.

Given this can slip-through easily when adding new types, make this an explicit
allow-list and reject all other current and future types by default if this is
encountered.

Also, extend check_ptr_off_reg() to handle PTR_TO_BTF_ID as well instead of
duplicating it. For PTR_TO_BTF_ID, reg->off is used for BTF to match expected
BTF ids if struct offset is used. This part still needs to be allowed, but the
dynamic off from the tnum must be rejected.

Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 6788ab23508bddb0a9d88e104284922cb2c22b77)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 61b8a9c69b1c..14813fbebc9f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3792,14 +3792,15 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ptr_off_reg(struct bpf_verifier_env *env,
-		      const struct bpf_reg_state *reg, int regno)
+static int __check_ptr_off_reg(struct bpf_verifier_env *env,
+			       const struct bpf_reg_state *reg, int regno,
+			       bool fixed_off_ok)
 {
 	/* Access to this pointer-typed register or passing it to a helper
 	 * is only allowed in its original, unmodified form.
 	 */
 
-	if (reg->off) {
+	if (!fixed_off_ok && reg->off) {
 		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
 			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
@@ -3817,6 +3818,12 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 	return 0;
 }
 
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
+{
+	return __check_ptr_off_reg(env, reg, regno, false);
+}
+
 static int __check_buffer_access(struct bpf_verifier_env *env,
 				 const char *buf_info,
 				 const struct bpf_reg_state *reg,
@@ -5080,12 +5087,6 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 				kernel_type_name(btf_vmlinux, *arg_btf_id));
 			return -EACCES;
 		}
-
-		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
-			verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
-				regno);
-			return -EACCES;
-		}
 	}
 
 	return 0;
@@ -5140,10 +5141,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	if (err)
 		return err;
 
-	if (type == PTR_TO_CTX) {
-		err = check_ptr_off_reg(env, reg, regno);
+	switch ((u32)type) {
+	case SCALAR_VALUE:
+	/* Pointer types where reg offset is explicitly allowed: */
+	case PTR_TO_PACKET:
+	case PTR_TO_PACKET_META:
+	case PTR_TO_MAP_KEY:
+	case PTR_TO_MAP_VALUE:
+	case PTR_TO_MEM:
+	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_BUF:
+	case PTR_TO_BUF | MEM_RDONLY:
+	case PTR_TO_STACK:
+		break;
+	/* All the rest must be rejected: */
+	default:
+		err = __check_ptr_off_reg(env, reg, regno,
+					  type == PTR_TO_BTF_ID);
 		if (err < 0)
 			return err;
+		break;
 	}
 
 skip_type_check:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y 4/5] bpf: Fix out of bounds access for ringbuf helpers
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (2 preceding siblings ...)
  2024-04-17 23:35   ` [PATCH 5.15.y 3/5] bpf: Generally fix helper register offset check Edward Liaw
@ 2024-04-17 23:35   ` Edward Liaw
  2024-04-17 23:35   ` [PATCH 5.15.y 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel, tr3e.wang

From: Daniel Borkmann <daniel@iogearbox.net>

Both bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument. They both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

Meaning, after a NULL check in the code, the verifier will promote the register
type in the non-NULL branch to a PTR_TO_MEM and in the NULL branch to a known
zero scalar. Generally, pointer arithmetic on PTR_TO_MEM is allowed, so the
latter could have an offset.

The ARG_PTR_TO_ALLOC_MEM expects a PTR_TO_MEM register type. However, the non-
zero result from bpf_ringbuf_reserve() must be fed into either bpf_ringbuf_submit()
or bpf_ringbuf_discard() but with the original offset given it will then read
out the struct bpf_ringbuf_hdr mapping.

The verifier missed to enforce a zero offset, so that out of bounds access
can be triggered which could be used to escalate privileges if unprivileged
BPF was enabled (disabled by default in kernel).

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: <tr3e.wang@gmail.com> (SecCoder Security Lab)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 64620e0a1e712a778095bd35cbb277dc2259281f)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 14813fbebc9f..3dfc45ed428a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5153,9 +5153,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
+		/* Some of the argument types nevertheless require a
+		 * zero register offset.
+		 */
+		if (arg_type == ARG_PTR_TO_ALLOC_MEM)
+			goto force_off_check;
 		break;
 	/* All the rest must be rejected: */
 	default:
+force_off_check:
 		err = __check_ptr_off_reg(env, reg, regno,
 					  type == PTR_TO_BTF_ID);
 		if (err < 0)
-- 
2.44.0.769.g3c40516874-goog

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (3 preceding siblings ...)
  2024-04-17 23:35   ` [PATCH 5.15.y 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
@ 2024-04-17 23:35   ` Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-17 23:35 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

The bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument, and thus both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

While the non-NULL memory from bpf_ringbuf_reserve() can be passed to other
helpers, the two sinks (bpf_ringbuf_submit(), bpf_ringbuf_discard()) right now
only enforce a register type of PTR_TO_MEM.

This can lead to potential type confusion since it would allow other PTR_TO_MEM
memory to be passed into the two sinks which did not come from bpf_ringbuf_reserve().

Add a new MEM_ALLOC composable type attribute for PTR_TO_MEM, and enforce that:

 - bpf_ringbuf_reserve() returns NULL or PTR_TO_MEM | MEM_ALLOC
 - bpf_ringbuf_submit() and bpf_ringbuf_discard() only take PTR_TO_MEM | MEM_ALLOC
   but not plain PTR_TO_MEM arguments via ARG_PTR_TO_ALLOC_MEM
 - however, other helpers might treat PTR_TO_MEM | MEM_ALLOC as plain PTR_TO_MEM
   to populate the memory area when they use ARG_PTR_TO_{UNINIT_,}MEM in their
   func proto description

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit a672b2e36a648afb04ad3bda93b6bda947a479a5)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf.h   | 9 +++++++--
 kernel/bpf/verifier.c | 6 +++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 84efd8dd139d..96b2aa567d23 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -312,7 +312,12 @@ enum bpf_type_flag {
 	 */
 	MEM_RDONLY		= BIT(1 + BPF_BASE_TYPE_BITS),
 
-	__BPF_TYPE_LAST_FLAG	= MEM_RDONLY,
+	/* MEM was "allocated" from a different helper, and cannot be mixed
+	 * with regular non-MEM_ALLOC'ed MEM types.
+	 */
+	MEM_ALLOC		= BIT(2 + BPF_BASE_TYPE_BITS),
+
+	__BPF_TYPE_LAST_FLAG	= MEM_ALLOC,
 };
 
 /* Max number of base types. */
@@ -396,7 +401,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
 	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
 	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
-	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
 	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
 
 	/* This must be the last entry. Its purpose is to ensure the enum is
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3dfc45ed428a..6162ba31a89e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -567,6 +567,8 @@ static const char *reg_type_str(struct bpf_verifier_env *env,
 
 	if (type & MEM_RDONLY)
 		strncpy(prefix, "rdonly_", 16);
+	if (type & MEM_ALLOC)
+		strncpy(prefix, "alloc_", 16);
 
 	snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s",
 		 prefix, str[base_type(type)], postfix);
@@ -4970,6 +4972,7 @@ static const struct bpf_reg_types mem_types = {
 		PTR_TO_MAP_KEY,
 		PTR_TO_MAP_VALUE,
 		PTR_TO_MEM,
+		PTR_TO_MEM | MEM_ALLOC,
 		PTR_TO_BUF,
 	},
 };
@@ -4987,7 +4990,7 @@ static const struct bpf_reg_types int_ptr_types = {
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
-static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
+static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM | MEM_ALLOC } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
 static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
@@ -5150,6 +5153,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_MAP_VALUE:
 	case PTR_TO_MEM:
 	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_MEM | MEM_ALLOC:
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf
       [not found] <16430256912363@kroah.com>
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
@ 2024-04-18  1:07 ` Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
                     ` (4 more replies)
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
  2 siblings, 5 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

These backports fix CVE-2021-4204, CVE-2022-23222 for 5.15.y.

This includes a conflict resolution with 45ce4b4f9009 ("bpf: Fix crash
due to out of bounds access into reg2btf_ids.") which was cherry-picked
previously.
Link: https://lore.kernel.org/all/20220428235751.103203-11-haoluo@google.com/

They were tested on 5.15.94 to pass LTP test bpf_prog06 with no
regressions from the bpf selftests.

v2:
Made a mistake of not including the out of bounds reg2btf_ids fix

Daniel Borkmann (4):
  bpf: Generalize check_ctx_reg for reuse with other types
  bpf: Generally fix helper register offset check
  bpf: Fix out of bounds access for ringbuf helpers
  bpf: Fix ringbuf memory type confusion when passing to helpers

Kumar Kartikeya Dwivedi (1):
  bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support

 include/linux/bpf.h          |  9 +++-
 include/linux/bpf_verifier.h |  4 +-
 kernel/bpf/btf.c             | 93 ++++++++++++++++++++++++++++--------
 kernel/bpf/verifier.c        | 66 +++++++++++++++++--------
 4 files changed, 129 insertions(+), 43 deletions(-)

--
2.44.0.769.g3c40516874-goog


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
@ 2024-04-18  1:07   ` Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
                     ` (3 subsequent siblings)
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel,
	Kumar Kartikeya Dwivedi

From: Kumar Kartikeya Dwivedi <memxor@gmail.com>

Allow passing PTR_TO_CTX, if the kfunc expects a matching struct type,
and punt to PTR_TO_MEM block if reg->type does not fall in one of
PTR_TO_BTF_ID or PTR_TO_SOCK* types. This will be used by future commits
to get access to XDP and TC PTR_TO_CTX, and pass various data (flags,
l4proto, netns_id, etc.) encoded in opts struct passed as pointer to
kfunc.

For PTR_TO_MEM support, arguments are currently limited to pointer to
scalar, or pointer to struct composed of scalars. This is done so that
unsafe scenarios (like passing PTR_TO_MEM where PTR_TO_BTF_ID of
in-kernel valid structure is expected, which may have pointers) are
avoided. Since the argument checking happens basd on argument register
type, it is not easy to ascertain what the expected type is. In the
future, support for PTR_TO_MEM for kfunc can be extended to serve other
usecases. The struct type whose pointer is passed in may have maximum
nesting depth of 4, all recursively composed of scalars or struct with
scalars.

Future commits will add negative tests that check whether these
restrictions imposed for kfunc arguments are duly rejected by BPF
verifier or not.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217015031.1278167-4-memxor@gmail.com
(cherry picked from commit 3363bd0cfbb80dfcd25003cd3815b0ad8b68d0ff)
[edliaw: fixed up with changes from 45ce4b4f90091 ("bpf: Fix crash due to out of bounds access into reg2btf_ids.")]
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/btf.c | 93 +++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 73 insertions(+), 20 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 0c2fa93bd8d2..9a0db26a3bfa 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5441,6 +5441,46 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 #endif
 };
 
+/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
+static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
+					const struct btf *btf,
+					const struct btf_type *t, int rec)
+{
+	const struct btf_type *member_type;
+	const struct btf_member *member;
+	u32 i;
+
+	if (!btf_type_is_struct(t))
+		return false;
+
+	for_each_member(i, t, member) {
+		const struct btf_array *array;
+
+		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
+		if (btf_type_is_struct(member_type)) {
+			if (rec >= 3) {
+				bpf_log(log, "max struct nesting depth exceeded\n");
+				return false;
+			}
+			if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
+				return false;
+			continue;
+		}
+		if (btf_type_is_array(member_type)) {
+			array = btf_type_array(member_type);
+			if (!array->nelems)
+				return false;
+			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
+			if (!btf_type_is_scalar(member_type))
+				return false;
+			continue;
+		}
+		if (!btf_type_is_scalar(member_type))
+			return false;
+	}
+	return true;
+}
+
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
@@ -5449,6 +5489,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 	enum bpf_prog_type prog_type = env->prog->type == BPF_PROG_TYPE_EXT ?
 		env->prog->aux->dst_prog->type : env->prog->type;
 	struct bpf_verifier_log *log = &env->log;
+	bool is_kfunc = btf_is_kernel(btf);
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
@@ -5501,7 +5542,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 
 		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
-		if (btf_is_kernel(btf)) {
+		if (btf_get_prog_ctx_type(log, btf, t,
+					  env->prog->type, i)) {
+			/* If function expects ctx type in BTF check that caller
+			 * is passing PTR_TO_CTX.
+			 */
+			if (reg->type != PTR_TO_CTX) {
+				bpf_log(log,
+					"arg#%d expected pointer to ctx, but got %s\n",
+					i, btf_type_str(t));
+				return -EINVAL;
+			}
+			if (check_ctx_reg(env, reg, regno))
+				return -EINVAL;
+		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
 			const struct btf_type *reg_ref_t;
 			const struct btf *reg_btf;
 			const char *reg_ref_tname;
@@ -5517,14 +5571,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (reg->type == PTR_TO_BTF_ID) {
 				reg_btf = reg->btf;
 				reg_ref_id = reg->btf_id;
-			} else if (reg2btf_ids[base_type(reg->type)]) {
+			} else {
 				reg_btf = btf_vmlinux;
 				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
-			} else {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d is not a pointer to btf_id\n",
-					func_name, i,
-					btf_type_str(ref_t), ref_tname, regno);
-				return -EINVAL;
 			}
 
 			reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
@@ -5540,22 +5589,24 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					reg_ref_tname);
 				return -EINVAL;
 			}
-		} else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
-			/* If function expects ctx type in BTF check that caller
-			 * is passing PTR_TO_CTX.
-			 */
-			if (reg->type != PTR_TO_CTX) {
-				bpf_log(log,
-					"arg#%d expected pointer to ctx, but got %s\n",
-					i, btf_type_str(t));
-				return -EINVAL;
-			}
-			if (check_ctx_reg(env, reg, regno))
-				return -EINVAL;
 		} else if (ptr_to_mem_ok) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;
 
+			if (is_kfunc) {
+				/* Permit pointer to mem, but only when argument
+				 * type is pointer to scalar, or struct composed
+				 * (recursively) of scalars.
+				 */
+				if (!btf_type_is_scalar(ref_t) &&
+				    !__btf_type_is_scalar_struct(log, btf, ref_t, 0)) {
+					bpf_log(log,
+						"arg#%d pointer type %s %s must point to scalar or struct with scalar\n",
+						i, btf_type_str(ref_t), ref_tname);
+					return -EINVAL;
+				}
+			}
+
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
 				bpf_log(log,
@@ -5568,6 +5619,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (check_mem_reg(env, reg, regno, type_size))
 				return -EINVAL;
 		} else {
+			bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
+				is_kfunc ? "kernel " : "", func_name, func_id);
 			return -EINVAL;
 		}
 	}
@@ -5617,7 +5670,7 @@ int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
 			      const struct btf *btf, u32 func_id,
 			      struct bpf_reg_state *regs)
 {
-	return btf_check_func_arg_match(env, btf, func_id, regs, false);
+	return btf_check_func_arg_match(env, btf, func_id, regs, true);
 }
 
 /* Convert BTF of a function into bpf_reg_state if possible
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 2/5] bpf: Generalize check_ctx_reg for reuse with other types
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
@ 2024-04-18  1:07   ` Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 3/5] bpf: Generally fix helper register offset check Edward Liaw
                     ` (2 subsequent siblings)
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Generalize the check_ctx_reg() helper function into a more generic named one
so that it can be reused for other register types as well to check whether
their offset is non-zero. No functional change.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf_verifier.h |  4 ++--
 kernel/bpf/btf.c             |  2 +-
 kernel/bpf/verifier.c        | 21 +++++++++++----------
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 3d04b48e502d..c0993b079ab5 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -541,8 +541,8 @@ bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
 void
 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno);
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
 
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 9a0db26a3bfa..be5bd4670296 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5553,7 +5553,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					i, btf_type_str(t));
 				return -EINVAL;
 			}
-			if (check_ctx_reg(env, reg, regno))
+			if (check_ptr_off_reg(env, reg, regno))
 				return -EINVAL;
 		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID || reg2btf_ids[base_type(reg->type)])) {
 			const struct btf_type *reg_ref_t;
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1c95d97e7aa5..61b8a9c69b1c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3792,16 +3792,16 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno)
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
 {
-	/* Access to ctx or passing it to a helper is only allowed in
-	 * its original, unmodified form.
+	/* Access to this pointer-typed register or passing it to a helper
+	 * is only allowed in its original, unmodified form.
 	 */
 
 	if (reg->off) {
-		verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
-			regno, reg->off);
+		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
 	}
 
@@ -3809,7 +3809,8 @@ int check_ctx_reg(struct bpf_verifier_env *env,
 		char tn_buf[48];
 
 		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-		verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
+		verbose(env, "variable %s access var_off=%s disallowed\n",
+			reg_type_str(env, reg->type), tn_buf);
 		return -EACCES;
 	}
 
@@ -4260,7 +4261,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 			return -EACCES;
 		}
 
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 
@@ -5140,7 +5141,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		return err;
 
 	if (type == PTR_TO_CTX) {
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 	}
@@ -9348,7 +9349,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			return err;
 	}
 
-	err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
+	err = check_ptr_off_reg(env, &regs[ctx_reg], ctx_reg);
 	if (err < 0)
 		return err;
 
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 3/5] bpf: Generally fix helper register offset check
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
@ 2024-04-18  1:07   ` Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Right now the assertion on check_ptr_off_reg() is only enforced for register
types PTR_TO_CTX (and open coded also for PTR_TO_BTF_ID), however, this is
insufficient since many other PTR_TO_* register types such as PTR_TO_FUNC do
not handle/expect register offsets when passed to helper functions.

Given this can slip-through easily when adding new types, make this an explicit
allow-list and reject all other current and future types by default if this is
encountered.

Also, extend check_ptr_off_reg() to handle PTR_TO_BTF_ID as well instead of
duplicating it. For PTR_TO_BTF_ID, reg->off is used for BTF to match expected
BTF ids if struct offset is used. This part still needs to be allowed, but the
dynamic off from the tnum must be rejected.

Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 6788ab23508bddb0a9d88e104284922cb2c22b77)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 61b8a9c69b1c..14813fbebc9f 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3792,14 +3792,15 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ptr_off_reg(struct bpf_verifier_env *env,
-		      const struct bpf_reg_state *reg, int regno)
+static int __check_ptr_off_reg(struct bpf_verifier_env *env,
+			       const struct bpf_reg_state *reg, int regno,
+			       bool fixed_off_ok)
 {
 	/* Access to this pointer-typed register or passing it to a helper
 	 * is only allowed in its original, unmodified form.
 	 */
 
-	if (reg->off) {
+	if (!fixed_off_ok && reg->off) {
 		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
 			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
@@ -3817,6 +3818,12 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 	return 0;
 }
 
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
+{
+	return __check_ptr_off_reg(env, reg, regno, false);
+}
+
 static int __check_buffer_access(struct bpf_verifier_env *env,
 				 const char *buf_info,
 				 const struct bpf_reg_state *reg,
@@ -5080,12 +5087,6 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 				kernel_type_name(btf_vmlinux, *arg_btf_id));
 			return -EACCES;
 		}
-
-		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
-			verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
-				regno);
-			return -EACCES;
-		}
 	}
 
 	return 0;
@@ -5140,10 +5141,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	if (err)
 		return err;
 
-	if (type == PTR_TO_CTX) {
-		err = check_ptr_off_reg(env, reg, regno);
+	switch ((u32)type) {
+	case SCALAR_VALUE:
+	/* Pointer types where reg offset is explicitly allowed: */
+	case PTR_TO_PACKET:
+	case PTR_TO_PACKET_META:
+	case PTR_TO_MAP_KEY:
+	case PTR_TO_MAP_VALUE:
+	case PTR_TO_MEM:
+	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_BUF:
+	case PTR_TO_BUF | MEM_RDONLY:
+	case PTR_TO_STACK:
+		break;
+	/* All the rest must be rejected: */
+	default:
+		err = __check_ptr_off_reg(env, reg, regno,
+					  type == PTR_TO_BTF_ID);
 		if (err < 0)
 			return err;
+		break;
 	}
 
 skip_type_check:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 4/5] bpf: Fix out of bounds access for ringbuf helpers
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (2 preceding siblings ...)
  2024-04-18  1:07   ` [PATCH 5.15.y v2 3/5] bpf: Generally fix helper register offset check Edward Liaw
@ 2024-04-18  1:07   ` Edward Liaw
  2024-04-18  1:07   ` [PATCH 5.15.y v2 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel, tr3e.wang

From: Daniel Borkmann <daniel@iogearbox.net>

Both bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument. They both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

Meaning, after a NULL check in the code, the verifier will promote the register
type in the non-NULL branch to a PTR_TO_MEM and in the NULL branch to a known
zero scalar. Generally, pointer arithmetic on PTR_TO_MEM is allowed, so the
latter could have an offset.

The ARG_PTR_TO_ALLOC_MEM expects a PTR_TO_MEM register type. However, the non-
zero result from bpf_ringbuf_reserve() must be fed into either bpf_ringbuf_submit()
or bpf_ringbuf_discard() but with the original offset given it will then read
out the struct bpf_ringbuf_hdr mapping.

The verifier missed to enforce a zero offset, so that out of bounds access
can be triggered which could be used to escalate privileges if unprivileged
BPF was enabled (disabled by default in kernel).

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: <tr3e.wang@gmail.com> (SecCoder Security Lab)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 64620e0a1e712a778095bd35cbb277dc2259281f)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 14813fbebc9f..3dfc45ed428a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5153,9 +5153,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
+		/* Some of the argument types nevertheless require a
+		 * zero register offset.
+		 */
+		if (arg_type == ARG_PTR_TO_ALLOC_MEM)
+			goto force_off_check;
 		break;
 	/* All the rest must be rejected: */
 	default:
+force_off_check:
 		err = __check_ptr_off_reg(env, reg, regno,
 					  type == PTR_TO_BTF_ID);
 		if (err < 0)
-- 
2.44.0.769.g3c40516874-goog

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v2 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (3 preceding siblings ...)
  2024-04-18  1:07   ` [PATCH 5.15.y v2 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
@ 2024-04-18  1:07   ` Edward Liaw
  4 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18  1:07 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	KP Singh, Hao Luo
  Cc: bpf, kernel-team, Edward Liaw, netdev, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

The bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument, and thus both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

While the non-NULL memory from bpf_ringbuf_reserve() can be passed to other
helpers, the two sinks (bpf_ringbuf_submit(), bpf_ringbuf_discard()) right now
only enforce a register type of PTR_TO_MEM.

This can lead to potential type confusion since it would allow other PTR_TO_MEM
memory to be passed into the two sinks which did not come from bpf_ringbuf_reserve().

Add a new MEM_ALLOC composable type attribute for PTR_TO_MEM, and enforce that:

 - bpf_ringbuf_reserve() returns NULL or PTR_TO_MEM | MEM_ALLOC
 - bpf_ringbuf_submit() and bpf_ringbuf_discard() only take PTR_TO_MEM | MEM_ALLOC
   but not plain PTR_TO_MEM arguments via ARG_PTR_TO_ALLOC_MEM
 - however, other helpers might treat PTR_TO_MEM | MEM_ALLOC as plain PTR_TO_MEM
   to populate the memory area when they use ARG_PTR_TO_{UNINIT_,}MEM in their
   func proto description

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit a672b2e36a648afb04ad3bda93b6bda947a479a5)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf.h   | 9 +++++++--
 kernel/bpf/verifier.c | 6 +++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 84efd8dd139d..96b2aa567d23 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -312,7 +312,12 @@ enum bpf_type_flag {
 	 */
 	MEM_RDONLY		= BIT(1 + BPF_BASE_TYPE_BITS),
 
-	__BPF_TYPE_LAST_FLAG	= MEM_RDONLY,
+	/* MEM was "allocated" from a different helper, and cannot be mixed
+	 * with regular non-MEM_ALLOC'ed MEM types.
+	 */
+	MEM_ALLOC		= BIT(2 + BPF_BASE_TYPE_BITS),
+
+	__BPF_TYPE_LAST_FLAG	= MEM_ALLOC,
 };
 
 /* Max number of base types. */
@@ -396,7 +401,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
 	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
 	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
-	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
 	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
 
 	/* This must be the last entry. Its purpose is to ensure the enum is
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 3dfc45ed428a..6162ba31a89e 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -567,6 +567,8 @@ static const char *reg_type_str(struct bpf_verifier_env *env,
 
 	if (type & MEM_RDONLY)
 		strncpy(prefix, "rdonly_", 16);
+	if (type & MEM_ALLOC)
+		strncpy(prefix, "alloc_", 16);
 
 	snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s",
 		 prefix, str[base_type(type)], postfix);
@@ -4970,6 +4972,7 @@ static const struct bpf_reg_types mem_types = {
 		PTR_TO_MAP_KEY,
 		PTR_TO_MAP_VALUE,
 		PTR_TO_MEM,
+		PTR_TO_MEM | MEM_ALLOC,
 		PTR_TO_BUF,
 	},
 };
@@ -4987,7 +4990,7 @@ static const struct bpf_reg_types int_ptr_types = {
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
-static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
+static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM | MEM_ALLOC } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
 static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
@@ -5150,6 +5153,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_MAP_VALUE:
 	case PTR_TO_MEM:
 	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_MEM | MEM_ALLOC:
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf
       [not found] <16430256912363@kroah.com>
  2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
@ 2024-04-18 23:19 ` Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
                     ` (5 more replies)
  2 siblings, 6 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel

These backports fix CVE-2021-4204, CVE-2022-23222 for 5.15.y.

This includes a conflict resolution with 45ce4b4f9009 ("bpf: Fix crash
due to out of bounds access into reg2btf_ids.") which was cherry-picked
previously.
Link: https://lore.kernel.org/all/20220428235751.103203-11-haoluo@google.com/

They were tested on 5.15.156 to pass LTP test bpf_prog06 with no
regressions in test_verifier in bpf selftests.

v2:
Made a mistake of not including the out of bounds reg2btf_ids fix
v3:
Merged in prog_type fix from f858c2b2ca04 ("bpf: Fix calling global
functions from BPF_PROG_TYPE_EXT programs") and rebased to 5.15.156


Daniel Borkmann (4):
  bpf: Generalize check_ctx_reg for reuse with other types
  bpf: Generally fix helper register offset check
  bpf: Fix out of bounds access for ringbuf helpers
  bpf: Fix ringbuf memory type confusion when passing to helpers

Edward Liaw (1):
  bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support

 include/linux/bpf.h          |  9 +++-
 include/linux/bpf_verifier.h |  4 +-
 kernel/bpf/btf.c             | 93 ++++++++++++++++++++++++++++--------
 kernel/bpf/verifier.c        | 66 +++++++++++++++++--------
 4 files changed, 129 insertions(+), 43 deletions(-)

--
2.44.0.769.g3c40516874-goog


^ permalink raw reply	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
@ 2024-04-18 23:19   ` Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
                     ` (4 subsequent siblings)
  5 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel,
	Kumar Kartikeya Dwivedi

Allow passing PTR_TO_CTX, if the kfunc expects a matching struct type,
and punt to PTR_TO_MEM block if reg->type does not fall in one of
PTR_TO_BTF_ID or PTR_TO_SOCK* types. This will be used by future commits
to get access to XDP and TC PTR_TO_CTX, and pass various data (flags,
l4proto, netns_id, etc.) encoded in opts struct passed as pointer to
kfunc.

For PTR_TO_MEM support, arguments are currently limited to pointer to
scalar, or pointer to struct composed of scalars. This is done so that
unsafe scenarios (like passing PTR_TO_MEM where PTR_TO_BTF_ID of
in-kernel valid structure is expected, which may have pointers) are
avoided. Since the argument checking happens basd on argument register
type, it is not easy to ascertain what the expected type is. In the
future, support for PTR_TO_MEM for kfunc can be extended to serve other
usecases. The struct type whose pointer is passed in may have maximum
nesting depth of 4, all recursively composed of scalars or struct with
scalars.

Future commits will add negative tests that check whether these
restrictions imposed for kfunc arguments are duly rejected by BPF
verifier or not.

[edliaw: merged with changes from 45ce4b4f90091 ("bpf: Fix crash due to
 out of bounds access into reg2btf_ids.") and f858c2b2ca04 ("bpf: Fix
 calling global functions from BPF_PROG_TYPE_EXT programs")]

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20211217015031.1278167-4-memxor@gmail.com
(cherry picked from commit 3363bd0cfbb80dfcd25003cd3815b0ad8b68d0ff)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/btf.c | 93 +++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 73 insertions(+), 20 deletions(-)

diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 5d4bea53ac1f..77929fd7bcef 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5447,6 +5447,46 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
 #endif
 };

+/* Returns true if struct is composed of scalars, 4 levels of nesting allowed */
+static bool __btf_type_is_scalar_struct(struct bpf_verifier_log *log,
+					const struct btf *btf,
+					const struct btf_type *t, int rec)
+{
+	const struct btf_type *member_type;
+	const struct btf_member *member;
+	u32 i;
+
+	if (!btf_type_is_struct(t))
+		return false;
+
+	for_each_member(i, t, member) {
+		const struct btf_array *array;
+
+		member_type = btf_type_skip_modifiers(btf, member->type, NULL);
+		if (btf_type_is_struct(member_type)) {
+			if (rec >= 3) {
+				bpf_log(log, "max struct nesting depth exceeded\n");
+				return false;
+			}
+			if (!__btf_type_is_scalar_struct(log, btf, member_type, rec + 1))
+				return false;
+			continue;
+		}
+		if (btf_type_is_array(member_type)) {
+			array = btf_type_array(member_type);
+			if (!array->nelems)
+				return false;
+			member_type = btf_type_skip_modifiers(btf, array->type, NULL);
+			if (!btf_type_is_scalar(member_type))
+				return false;
+			continue;
+		}
+		if (!btf_type_is_scalar(member_type))
+			return false;
+	}
+	return true;
+}
+
 static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 				    const struct btf *btf, u32 func_id,
 				    struct bpf_reg_state *regs,
@@ -5455,6 +5495,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 	enum bpf_prog_type prog_type = env->prog->type == BPF_PROG_TYPE_EXT ?
 		env->prog->aux->dst_prog->type : env->prog->type;
 	struct bpf_verifier_log *log = &env->log;
+	bool is_kfunc = btf_is_kernel(btf);
 	const char *func_name, *ref_tname;
 	const struct btf_type *t, *ref_t;
 	const struct btf_param *args;
@@ -5507,7 +5548,20 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,

 		ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 		ref_tname = btf_name_by_offset(btf, ref_t->name_off);
-		if (btf_is_kernel(btf)) {
+		if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
+			/* If function expects ctx type in BTF check that caller
+			 * is passing PTR_TO_CTX.
+			 */
+			if (reg->type != PTR_TO_CTX) {
+				bpf_log(log,
+					"arg#%d expected pointer to ctx, but got %s\n",
+					i, btf_type_str(t));
+				return -EINVAL;
+			}
+			if (check_ctx_reg(env, reg, regno))
+				return -EINVAL;
+		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
+			   (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
 			const struct btf_type *reg_ref_t;
 			const struct btf *reg_btf;
 			const char *reg_ref_tname;
@@ -5523,14 +5577,9 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (reg->type == PTR_TO_BTF_ID) {
 				reg_btf = reg->btf;
 				reg_ref_id = reg->btf_id;
-			} else if (reg2btf_ids[base_type(reg->type)]) {
+			} else {
 				reg_btf = btf_vmlinux;
 				reg_ref_id = *reg2btf_ids[base_type(reg->type)];
-			} else {
-				bpf_log(log, "kernel function %s args#%d expected pointer to %s %s but R%d is not a pointer to btf_id\n",
-					func_name, i,
-					btf_type_str(ref_t), ref_tname, regno);
-				return -EINVAL;
 			}

 			reg_ref_t = btf_type_skip_modifiers(reg_btf, reg_ref_id,
@@ -5546,22 +5595,24 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					reg_ref_tname);
 				return -EINVAL;
 			}
-		} else if (btf_get_prog_ctx_type(log, btf, t, prog_type, i)) {
-			/* If function expects ctx type in BTF check that caller
-			 * is passing PTR_TO_CTX.
-			 */
-			if (reg->type != PTR_TO_CTX) {
-				bpf_log(log,
-					"arg#%d expected pointer to ctx, but got %s\n",
-					i, btf_type_str(t));
-				return -EINVAL;
-			}
-			if (check_ctx_reg(env, reg, regno))
-				return -EINVAL;
 		} else if (ptr_to_mem_ok) {
 			const struct btf_type *resolve_ret;
 			u32 type_size;

+			if (is_kfunc) {
+				/* Permit pointer to mem, but only when argument
+				 * type is pointer to scalar, or struct composed
+				 * (recursively) of scalars.
+				 */
+				if (!btf_type_is_scalar(ref_t) &&
+				    !__btf_type_is_scalar_struct(log, btf, ref_t, 0)) {
+					bpf_log(log,
+						"arg#%d pointer type %s %s must point to scalar or struct with scalar\n",
+						i, btf_type_str(ref_t), ref_tname);
+					return -EINVAL;
+				}
+			}
+
 			resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 			if (IS_ERR(resolve_ret)) {
 				bpf_log(log,
@@ -5574,6 +5625,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 			if (check_mem_reg(env, reg, regno, type_size))
 				return -EINVAL;
 		} else {
+			bpf_log(log, "reg type unsupported for arg#%d %sfunction %s#%d\n", i,
+				is_kfunc ? "kernel " : "", func_name, func_id);
 			return -EINVAL;
 		}
 	}
@@ -5623,7 +5676,7 @@ int btf_check_kfunc_arg_match(struct bpf_verifier_env *env,
 			      const struct btf *btf, u32 func_id,
 			      struct bpf_reg_state *regs)
 {
-	return btf_check_func_arg_match(env, btf, func_id, regs, false);
+	return btf_check_func_arg_match(env, btf, func_id, regs, true);
 }

 /* Convert BTF of a function into bpf_reg_state if possible
--
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 2/5] bpf: Generalize check_ctx_reg for reuse with other types
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
@ 2024-04-18 23:19   ` Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 3/5] bpf: Generally fix helper register offset check Edward Liaw
                     ` (3 subsequent siblings)
  5 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Generalize the check_ctx_reg() helper function into a more generic named one
so that it can be reused for other register types as well to check whether
their offset is non-zero. No functional change.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit be80a1d3f9dbe5aee79a325964f7037fe2d92f30)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf_verifier.h |  4 ++--
 kernel/bpf/btf.c             |  2 +-
 kernel/bpf/verifier.c        | 21 +++++++++++----------
 3 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 3d04b48e502d..c0993b079ab5 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -541,8 +541,8 @@ bpf_prog_offload_replace_insn(struct bpf_verifier_env *env, u32 off,
 void
 bpf_prog_offload_remove_insns(struct bpf_verifier_env *env, u32 off, u32 cnt);
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno);
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno);
 int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 		   u32 regno, u32 mem_size);
 
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 77929fd7bcef..a0c7e13e0ab4 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -5558,7 +5558,7 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env,
 					i, btf_type_str(t));
 				return -EINVAL;
 			}
-			if (check_ctx_reg(env, reg, regno))
+			if (check_ptr_off_reg(env, reg, regno))
 				return -EINVAL;
 		} else if (is_kfunc && (reg->type == PTR_TO_BTF_ID ||
 			   (reg2btf_ids[base_type(reg->type)] && !type_flag(reg->type)))) {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 008ddb694c8a..6fe805b559c0 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3980,16 +3980,16 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ctx_reg(struct bpf_verifier_env *env,
-		  const struct bpf_reg_state *reg, int regno)
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
 {
-	/* Access to ctx or passing it to a helper is only allowed in
-	 * its original, unmodified form.
+	/* Access to this pointer-typed register or passing it to a helper
+	 * is only allowed in its original, unmodified form.
 	 */
 
 	if (reg->off) {
-		verbose(env, "dereference of modified ctx ptr R%d off=%d disallowed\n",
-			regno, reg->off);
+		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
+			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
 	}
 
@@ -3997,7 +3997,8 @@ int check_ctx_reg(struct bpf_verifier_env *env,
 		char tn_buf[48];
 
 		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
-		verbose(env, "variable ctx access var_off=%s disallowed\n", tn_buf);
+		verbose(env, "variable %s access var_off=%s disallowed\n",
+			reg_type_str(env, reg->type), tn_buf);
 		return -EACCES;
 	}
 
@@ -4447,7 +4448,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
 			return -EACCES;
 		}
 
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 
@@ -5327,7 +5328,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		return err;
 
 	if (type == PTR_TO_CTX) {
-		err = check_ctx_reg(env, reg, regno);
+		err = check_ptr_off_reg(env, reg, regno);
 		if (err < 0)
 			return err;
 	}
@@ -9561,7 +9562,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			return err;
 	}
 
-	err = check_ctx_reg(env, &regs[ctx_reg], ctx_reg);
+	err = check_ptr_off_reg(env, &regs[ctx_reg], ctx_reg);
 	if (err < 0)
 		return err;
 
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 3/5] bpf: Generally fix helper register offset check
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
@ 2024-04-18 23:19   ` Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
                     ` (2 subsequent siblings)
  5 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

Right now the assertion on check_ptr_off_reg() is only enforced for register
types PTR_TO_CTX (and open coded also for PTR_TO_BTF_ID), however, this is
insufficient since many other PTR_TO_* register types such as PTR_TO_FUNC do
not handle/expect register offsets when passed to helper functions.

Given this can slip-through easily when adding new types, make this an explicit
allow-list and reject all other current and future types by default if this is
encountered.

Also, extend check_ptr_off_reg() to handle PTR_TO_BTF_ID as well instead of
duplicating it. For PTR_TO_BTF_ID, reg->off is used for BTF to match expected
BTF ids if struct offset is used. This part still needs to be allowed, but the
dynamic off from the tnum must be rejected.

Fixes: 69c087ba6225 ("bpf: Add bpf_for_each_map_elem() helper")
Fixes: eaa6bcb71ef6 ("bpf: Introduce bpf_per_cpu_ptr()")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 6788ab23508bddb0a9d88e104284922cb2c22b77)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 39 ++++++++++++++++++++++++++++-----------
 1 file changed, 28 insertions(+), 11 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6fe805b559c0..8cd265d1df34 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3980,14 +3980,15 @@ static int get_callee_stack_depth(struct bpf_verifier_env *env,
 }
 #endif
 
-int check_ptr_off_reg(struct bpf_verifier_env *env,
-		      const struct bpf_reg_state *reg, int regno)
+static int __check_ptr_off_reg(struct bpf_verifier_env *env,
+			       const struct bpf_reg_state *reg, int regno,
+			       bool fixed_off_ok)
 {
 	/* Access to this pointer-typed register or passing it to a helper
 	 * is only allowed in its original, unmodified form.
 	 */
 
-	if (reg->off) {
+	if (!fixed_off_ok && reg->off) {
 		verbose(env, "dereference of modified %s ptr R%d off=%d disallowed\n",
 			reg_type_str(env, reg->type), regno, reg->off);
 		return -EACCES;
@@ -4005,6 +4006,12 @@ int check_ptr_off_reg(struct bpf_verifier_env *env,
 	return 0;
 }
 
+int check_ptr_off_reg(struct bpf_verifier_env *env,
+		      const struct bpf_reg_state *reg, int regno)
+{
+	return __check_ptr_off_reg(env, reg, regno, false);
+}
+
 static int __check_buffer_access(struct bpf_verifier_env *env,
 				 const char *buf_info,
 				 const struct bpf_reg_state *reg,
@@ -5267,12 +5274,6 @@ static int check_reg_type(struct bpf_verifier_env *env, u32 regno,
 				kernel_type_name(btf_vmlinux, *arg_btf_id));
 			return -EACCES;
 		}
-
-		if (!tnum_is_const(reg->var_off) || reg->var_off.value) {
-			verbose(env, "R%d is a pointer to in-kernel struct with non-zero offset\n",
-				regno);
-			return -EACCES;
-		}
 	}
 
 	return 0;
@@ -5327,10 +5328,26 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	if (err)
 		return err;
 
-	if (type == PTR_TO_CTX) {
-		err = check_ptr_off_reg(env, reg, regno);
+	switch ((u32)type) {
+	case SCALAR_VALUE:
+	/* Pointer types where reg offset is explicitly allowed: */
+	case PTR_TO_PACKET:
+	case PTR_TO_PACKET_META:
+	case PTR_TO_MAP_KEY:
+	case PTR_TO_MAP_VALUE:
+	case PTR_TO_MEM:
+	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_BUF:
+	case PTR_TO_BUF | MEM_RDONLY:
+	case PTR_TO_STACK:
+		break;
+	/* All the rest must be rejected: */
+	default:
+		err = __check_ptr_off_reg(env, reg, regno,
+					  type == PTR_TO_BTF_ID);
 		if (err < 0)
 			return err;
+		break;
 	}
 
 skip_type_check:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 4/5] bpf: Fix out of bounds access for ringbuf helpers
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (2 preceding siblings ...)
  2024-04-18 23:19   ` [PATCH 5.15.y v3 3/5] bpf: Generally fix helper register offset check Edward Liaw
@ 2024-04-18 23:19   ` Edward Liaw
  2024-04-18 23:19   ` [PATCH 5.15.y v3 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
  2024-04-19 11:09   ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Greg KH
  5 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel,
	tr3e.wang

From: Daniel Borkmann <daniel@iogearbox.net>

Both bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument. They both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

Meaning, after a NULL check in the code, the verifier will promote the register
type in the non-NULL branch to a PTR_TO_MEM and in the NULL branch to a known
zero scalar. Generally, pointer arithmetic on PTR_TO_MEM is allowed, so the
latter could have an offset.

The ARG_PTR_TO_ALLOC_MEM expects a PTR_TO_MEM register type. However, the non-
zero result from bpf_ringbuf_reserve() must be fed into either bpf_ringbuf_submit()
or bpf_ringbuf_discard() but with the original offset given it will then read
out the struct bpf_ringbuf_hdr mapping.

The verifier missed to enforce a zero offset, so that out of bounds access
can be triggered which could be used to escalate privileges if unprivileged
BPF was enabled (disabled by default in kernel).

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: <tr3e.wang@gmail.com> (SecCoder Security Lab)
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit 64620e0a1e712a778095bd35cbb277dc2259281f)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 kernel/bpf/verifier.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8cd265d1df34..33fb379b9f58 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5340,9 +5340,15 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
+		/* Some of the argument types nevertheless require a
+		 * zero register offset.
+		 */
+		if (arg_type == ARG_PTR_TO_ALLOC_MEM)
+			goto force_off_check;
 		break;
 	/* All the rest must be rejected: */
 	default:
+force_off_check:
 		err = __check_ptr_off_reg(env, reg, regno,
 					  type == PTR_TO_BTF_ID);
 		if (err < 0)
-- 
2.44.0.769.g3c40516874-goog

^ permalink raw reply related	[flat|nested] 19+ messages in thread

* [PATCH 5.15.y v3 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (3 preceding siblings ...)
  2024-04-18 23:19   ` [PATCH 5.15.y v3 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
@ 2024-04-18 23:19   ` Edward Liaw
  2024-04-19 11:09   ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Greg KH
  5 siblings, 0 replies; 19+ messages in thread
From: Edward Liaw @ 2024-04-18 23:19 UTC (permalink / raw)
  To: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa
  Cc: bpf, kernel-team, Edward Liaw, Yonghong Song, linux-kernel

From: Daniel Borkmann <daniel@iogearbox.net>

The bpf_ringbuf_submit() and bpf_ringbuf_discard() have ARG_PTR_TO_ALLOC_MEM
in their bpf_func_proto definition as their first argument, and thus both expect
the result from a prior bpf_ringbuf_reserve() call which has a return type of
RET_PTR_TO_ALLOC_MEM_OR_NULL.

While the non-NULL memory from bpf_ringbuf_reserve() can be passed to other
helpers, the two sinks (bpf_ringbuf_submit(), bpf_ringbuf_discard()) right now
only enforce a register type of PTR_TO_MEM.

This can lead to potential type confusion since it would allow other PTR_TO_MEM
memory to be passed into the two sinks which did not come from bpf_ringbuf_reserve().

Add a new MEM_ALLOC composable type attribute for PTR_TO_MEM, and enforce that:

 - bpf_ringbuf_reserve() returns NULL or PTR_TO_MEM | MEM_ALLOC
 - bpf_ringbuf_submit() and bpf_ringbuf_discard() only take PTR_TO_MEM | MEM_ALLOC
   but not plain PTR_TO_MEM arguments via ARG_PTR_TO_ALLOC_MEM
 - however, other helpers might treat PTR_TO_MEM | MEM_ALLOC as plain PTR_TO_MEM
   to populate the memory area when they use ARG_PTR_TO_{UNINIT_,}MEM in their
   func proto description

Fixes: 457f44363a88 ("bpf: Implement BPF ring buffer and verifier support for it")
Reported-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
(cherry picked from commit a672b2e36a648afb04ad3bda93b6bda947a479a5)
Signed-off-by: Edward Liaw <edliaw@google.com>
---
 include/linux/bpf.h   | 9 +++++++--
 kernel/bpf/verifier.c | 6 +++++-
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index df15d4d445dd..74a26cabc084 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -321,7 +321,12 @@ enum bpf_type_flag {
 	 */
 	MEM_RDONLY		= BIT(1 + BPF_BASE_TYPE_BITS),
 
-	__BPF_TYPE_LAST_FLAG	= MEM_RDONLY,
+	/* MEM was "allocated" from a different helper, and cannot be mixed
+	 * with regular non-MEM_ALLOC'ed MEM types.
+	 */
+	MEM_ALLOC		= BIT(2 + BPF_BASE_TYPE_BITS),
+
+	__BPF_TYPE_LAST_FLAG	= MEM_ALLOC,
 };
 
 /* Max number of base types. */
@@ -405,7 +410,7 @@ enum bpf_return_type {
 	RET_PTR_TO_SOCKET_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCKET,
 	RET_PTR_TO_TCP_SOCK_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_TCP_SOCK,
 	RET_PTR_TO_SOCK_COMMON_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_SOCK_COMMON,
-	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_ALLOC_MEM,
+	RET_PTR_TO_ALLOC_MEM_OR_NULL	= PTR_MAYBE_NULL | MEM_ALLOC | RET_PTR_TO_ALLOC_MEM,
 	RET_PTR_TO_BTF_ID_OR_NULL	= PTR_MAYBE_NULL | RET_PTR_TO_BTF_ID,
 
 	/* This must be the last entry. Its purpose is to ensure the enum is
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 33fb379b9f58..67b325427022 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -573,6 +573,8 @@ static const char *reg_type_str(struct bpf_verifier_env *env,
 
 	if (type & MEM_RDONLY)
 		strncpy(prefix, "rdonly_", 16);
+	if (type & MEM_ALLOC)
+		strncpy(prefix, "alloc_", 16);
 
 	snprintf(env->type_str_buf, TYPE_STR_BUF_LEN, "%s%s%s",
 		 prefix, str[base_type(type)], postfix);
@@ -5157,6 +5159,7 @@ static const struct bpf_reg_types mem_types = {
 		PTR_TO_MAP_KEY,
 		PTR_TO_MAP_VALUE,
 		PTR_TO_MEM,
+		PTR_TO_MEM | MEM_ALLOC,
 		PTR_TO_BUF,
 	},
 };
@@ -5174,7 +5177,7 @@ static const struct bpf_reg_types int_ptr_types = {
 static const struct bpf_reg_types fullsock_types = { .types = { PTR_TO_SOCKET } };
 static const struct bpf_reg_types scalar_types = { .types = { SCALAR_VALUE } };
 static const struct bpf_reg_types context_types = { .types = { PTR_TO_CTX } };
-static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM } };
+static const struct bpf_reg_types alloc_mem_types = { .types = { PTR_TO_MEM | MEM_ALLOC } };
 static const struct bpf_reg_types const_map_ptr_types = { .types = { CONST_PTR_TO_MAP } };
 static const struct bpf_reg_types btf_ptr_types = { .types = { PTR_TO_BTF_ID } };
 static const struct bpf_reg_types spin_lock_types = { .types = { PTR_TO_MAP_VALUE } };
@@ -5337,6 +5340,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	case PTR_TO_MAP_VALUE:
 	case PTR_TO_MEM:
 	case PTR_TO_MEM | MEM_RDONLY:
+	case PTR_TO_MEM | MEM_ALLOC:
 	case PTR_TO_BUF:
 	case PTR_TO_BUF | MEM_RDONLY:
 	case PTR_TO_STACK:
-- 
2.44.0.769.g3c40516874-goog


^ permalink raw reply related	[flat|nested] 19+ messages in thread

* Re: [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf
  2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
                     ` (4 preceding siblings ...)
  2024-04-18 23:19   ` [PATCH 5.15.y v3 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
@ 2024-04-19 11:09   ` Greg KH
  5 siblings, 0 replies; 19+ messages in thread
From: Greg KH @ 2024-04-19 11:09 UTC (permalink / raw)
  To: Edward Liaw
  Cc: stable, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
	Martin KaFai Lau, Eduard Zingerman, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, Stanislav Fomichev, Hao Luo, Jiri Olsa,
	bpf, kernel-team, Yonghong Song, linux-kernel

On Thu, Apr 18, 2024 at 11:19:46PM +0000, Edward Liaw wrote:
> These backports fix CVE-2021-4204, CVE-2022-23222 for 5.15.y.
> 
> This includes a conflict resolution with 45ce4b4f9009 ("bpf: Fix crash
> due to out of bounds access into reg2btf_ids.") which was cherry-picked
> previously.
> Link: https://lore.kernel.org/all/20220428235751.103203-11-haoluo@google.com/
> 
> They were tested on 5.15.156 to pass LTP test bpf_prog06 with no
> regressions in test_verifier in bpf selftests.

All now applied, thanks.

greg k-h

^ permalink raw reply	[flat|nested] 19+ messages in thread

end of thread, other threads:[~2024-04-19 11:09 UTC | newest]

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2024-04-17 23:35 ` [PATCH 5.15.y 0/5] Backport bounds checks for bpf Edward Liaw
2024-04-17 23:35   ` [PATCH 5.15.y 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
2024-04-17 23:35   ` [PATCH 5.15.y 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
2024-04-17 23:35   ` [PATCH 5.15.y 3/5] bpf: Generally fix helper register offset check Edward Liaw
2024-04-17 23:35   ` [PATCH 5.15.y 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
2024-04-17 23:35   ` [PATCH 5.15.y 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
2024-04-18  1:07 ` [PATCH 5.15.y v2 0/5] Backport bounds checks for bpf Edward Liaw
2024-04-18  1:07   ` [PATCH 5.15.y v2 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
2024-04-18  1:07   ` [PATCH 5.15.y v2 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
2024-04-18  1:07   ` [PATCH 5.15.y v2 3/5] bpf: Generally fix helper register offset check Edward Liaw
2024-04-18  1:07   ` [PATCH 5.15.y v2 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
2024-04-18  1:07   ` [PATCH 5.15.y v2 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
2024-04-18 23:19 ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Edward Liaw
2024-04-18 23:19   ` [PATCH 5.15.y v3 1/5] bpf: Extend kfunc with PTR_TO_CTX, PTR_TO_MEM argument support Edward Liaw
2024-04-18 23:19   ` [PATCH 5.15.y v3 2/5] bpf: Generalize check_ctx_reg for reuse with other types Edward Liaw
2024-04-18 23:19   ` [PATCH 5.15.y v3 3/5] bpf: Generally fix helper register offset check Edward Liaw
2024-04-18 23:19   ` [PATCH 5.15.y v3 4/5] bpf: Fix out of bounds access for ringbuf helpers Edward Liaw
2024-04-18 23:19   ` [PATCH 5.15.y v3 5/5] bpf: Fix ringbuf memory type confusion when passing to helpers Edward Liaw
2024-04-19 11:09   ` [PATCH 5.15.y v3 0/5] Backport bounds checks for bpf Greg KH

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