netdev - [PATCHv14 bpf-next 2/6] bpf: add a new bpf argument type ARG_CONST_MAP_PTR_OR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210114142321.2594697-3-liuhangbin@gmail.com>
Date:   Thu, 14 Jan 2021 22:23:17 +0800
From:   Hangbin Liu <liuhangbin@...il.com>
To:     bpf@...r.kernel.org
Cc:     netdev@...r.kernel.org,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        Jiri Benc <jbenc@...hat.com>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Eelco Chaudron <echaudro@...hat.com>, ast@...nel.org,
        Daniel Borkmann <daniel@...earbox.net>,
        Lorenzo Bianconi <lorenzo.bianconi@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Hangbin Liu <liuhangbin@...il.com>
Subject: [PATCHv14 bpf-next 2/6] bpf: add a new bpf argument type ARG_CONST_MAP_PTR_OR_NULL

Add a new bpf argument type ARG_CONST_MAP_PTR_OR_NULL which could be
used when we want to allow NULL pointer for map parameter. The bpf helper
need to take care and check if the map is NULL when use this type.

Signed-off-by: Hangbin Liu <liuhangbin@...il.com>

---
v11-v14: rebase the patch to latest bpf-next
v10: remove useless CONST_PTR_TO_MAP_OR_NULL and Copy-paste comment.
v9: merge the patch from [1] in to this series.
v1-v8: no this patch

[1] https://lore.kernel.org/bpf/20200715070001.2048207-1-liuhangbin@gmail.com/

---
 include/linux/bpf.h   |  1 +
 kernel/bpf/verifier.c | 10 ++++++----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 1aac2af12fed..b75207a2484c 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -296,6 +296,7 @@ enum bpf_arg_type {
 	ARG_CONST_ALLOC_SIZE_OR_ZERO,	/* number of allocated bytes requested */
 	ARG_PTR_TO_BTF_ID_SOCK_COMMON,	/* pointer to in-kernel sock_common or bpf-mirrored bpf_sock */
 	ARG_PTR_TO_PERCPU_BTF_ID,	/* pointer to in-kernel percpu type */
+	ARG_CONST_MAP_PTR_OR_NULL,	/* const argument used as pointer to bpf_map or NULL */
 	__BPF_ARG_TYPE_MAX,
 };
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ae2aee48cf82..3e4b5d9fce78 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -445,7 +445,8 @@ static bool arg_type_may_be_null(enum bpf_arg_type type)
 	       type == ARG_PTR_TO_MEM_OR_NULL ||
 	       type == ARG_PTR_TO_CTX_OR_NULL ||
 	       type == ARG_PTR_TO_SOCKET_OR_NULL ||
-	       type == ARG_PTR_TO_ALLOC_MEM_OR_NULL;
+	       type == ARG_PTR_TO_ALLOC_MEM_OR_NULL ||
+	       type == ARG_CONST_MAP_PTR_OR_NULL;
 }
 
 /* Determine whether the function releases some resources allocated by another
@@ -4065,6 +4066,7 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_CONST_SIZE_OR_ZERO]	= &scalar_types,
 	[ARG_CONST_ALLOC_SIZE_OR_ZERO]	= &scalar_types,
 	[ARG_CONST_MAP_PTR]		= &const_map_ptr_types,
+	[ARG_CONST_MAP_PTR_OR_NULL]	= &const_map_ptr_types,
 	[ARG_PTR_TO_CTX]		= &context_types,
 	[ARG_PTR_TO_CTX_OR_NULL]	= &context_types,
 	[ARG_PTR_TO_SOCK_COMMON]	= &sock_types,
@@ -4210,9 +4212,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		meta->ref_obj_id = reg->ref_obj_id;
 	}
 
-	if (arg_type == ARG_CONST_MAP_PTR) {
-		/* bpf_map_xxx(map_ptr) call: remember that map_ptr */
-		meta->map_ptr = reg->map_ptr;
+	if (arg_type == ARG_CONST_MAP_PTR ||
+	    arg_type == ARG_CONST_MAP_PTR_OR_NULL) {
+		meta->map_ptr = register_is_null(reg) ? NULL : reg->map_ptr;
 	} else if (arg_type == ARG_PTR_TO_MAP_KEY) {
 		/* bpf_map_xxx(..., map_ptr, ..., key) call:
 		 * check that [key, key + map->key_size) are within
-- 
2.26.2