Add a new field, "prog_flags", and an initial flag value BPF_F_STRCIT_ALIGNMENT.
When set, the verifier will enforce strict pointer alignment regardless of the setting of CONFIG_EFFICIENT_UNALIGNED_ACCESS. The verifier, in this mode, will also use a fixed value of "2" in place of NET_IP_ALIGN. This facilitates test cases that will exercise and validate this part of the verifier even when run on architectures where alignment doesn't matter. Signed-off-by: David S. Miller <[email protected]> --- include/uapi/linux/bpf.h | 8 ++++++++ kernel/bpf/syscall.c | 5 ++++- kernel/bpf/verifier.c | 20 ++++++++++++++++---- tools/build/feature/test-bpf.c | 1 + tools/include/uapi/linux/bpf.h | 11 +++++++++-- 5 files changed, 38 insertions(+), 7 deletions(-) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 945a1f5..94dfa9d 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -132,6 +132,13 @@ enum bpf_attach_type { */ #define BPF_F_ALLOW_OVERRIDE (1U << 0) +/* If BPF_F_STRICT_ALIGNMENT is used in BPF_PROG_LOAD command, the + * verifier will perform strict alignment checking as if the kernel + * has been built with CONFIG_EFFICIENT_UNALIGNED_ACCESS not set, + * and NET_IP_ALIGN defined to 2. + */ +#define BPF_F_STRICT_ALIGNMENT (1U << 0) + #define BPF_PSEUDO_MAP_FD 1 /* flags for BPF_MAP_UPDATE_ELEM command */ @@ -177,6 +184,7 @@ union bpf_attr { __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied buffer */ __u32 kern_version; /* checked when prog_type=kprobe */ + __u32 prog_flags; }; struct { /* anonymous struct used by BPF_OBJ_* commands */ diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index fd2411f..265a0d8 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -783,7 +783,7 @@ struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type) EXPORT_SYMBOL_GPL(bpf_prog_get_type); /* last field in 'union bpf_attr' used by this command */ -#define BPF_PROG_LOAD_LAST_FIELD kern_version +#define BPF_PROG_LOAD_LAST_FIELD prog_flags static int bpf_prog_load(union bpf_attr *attr) { @@ -796,6 +796,9 @@ static int bpf_prog_load(union bpf_attr *attr) if (CHECK_ATTR(BPF_PROG_LOAD)) return -EINVAL; + if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT) + return -EINVAL; + /* copy eBPF program license from user space */ if (strncpy_from_user(license, u64_to_user_ptr(attr->license), sizeof(license) - 1) < 0) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index e1effce..a406555 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -796,6 +796,7 @@ static bool is_pointer_value(struct bpf_verifier_env *env, int regno) static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, int off, int size, bool strict) { + int ip_align; int reg_off; /* Byte size accesses are always allowed. */ @@ -812,10 +813,14 @@ static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, reg_off += reg->aux_off; } - /* skb->data is NET_IP_ALIGN-ed */ - if ((NET_IP_ALIGN + reg_off + off) % size != 0) { + /* skb->data is NET_IP_ALIGN-ed, but for strict alignment checking + * we force this to 2 which is universally what architectures use + * when they don't set CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS. + */ + ip_align = strict ? 2 : NET_IP_ALIGN; + if ((ip_align + reg_off + off) % size != 0) { verbose("misaligned packet access off %d+%d+%d size %d\n", - NET_IP_ALIGN, reg_off, off, size); + ip_align, reg_off, off, size); return -EACCES; } @@ -833,10 +838,12 @@ static int check_val_ptr_alignment(const struct bpf_reg_state *reg, return 0; } +static bool strict_alignment; + static int check_ptr_alignment(const struct bpf_reg_state *reg, int off, int size) { - bool strict = false; + bool strict = strict_alignment; if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) strict = true; @@ -3574,6 +3581,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) } else { log_level = 0; } + if (attr->prog_flags & BPF_F_STRICT_ALIGNMENT) + strict_alignment = true; + else + strict_alignment = false; ret = replace_map_fd_with_map_ptr(env); if (ret < 0) @@ -3679,6 +3690,7 @@ int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, mutex_lock(&bpf_verifier_lock); log_level = 0; + strict_alignment = false; env->explored_states = kcalloc(env->prog->len, sizeof(struct bpf_verifier_state_list *), diff --git a/tools/build/feature/test-bpf.c b/tools/build/feature/test-bpf.c index ebc6dce..7598361 100644 --- a/tools/build/feature/test-bpf.c +++ b/tools/build/feature/test-bpf.c @@ -29,6 +29,7 @@ int main(void) attr.log_size = 0; attr.log_level = 0; attr.kern_version = 0; + attr.prog_flags = 0; /* * Test existence of __NR_bpf and BPF_PROG_LOAD. diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index e553529..94dfa9d 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -132,6 +132,13 @@ enum bpf_attach_type { */ #define BPF_F_ALLOW_OVERRIDE (1U << 0) +/* If BPF_F_STRICT_ALIGNMENT is used in BPF_PROG_LOAD command, the + * verifier will perform strict alignment checking as if the kernel + * has been built with CONFIG_EFFICIENT_UNALIGNED_ACCESS not set, + * and NET_IP_ALIGN defined to 2. + */ +#define BPF_F_STRICT_ALIGNMENT (1U << 0) + #define BPF_PSEUDO_MAP_FD 1 /* flags for BPF_MAP_UPDATE_ELEM command */ @@ -177,6 +184,7 @@ union bpf_attr { __u32 log_size; /* size of user buffer */ __aligned_u64 log_buf; /* user supplied buffer */ __u32 kern_version; /* checked when prog_type=kprobe */ + __u32 prog_flags; }; struct { /* anonymous struct used by BPF_OBJ_* commands */ @@ -481,8 +489,7 @@ union bpf_attr { * u32 bpf_get_socket_uid(skb) * Get the owner uid of the socket stored inside sk_buff. * @skb: pointer to skb - * Return: uid of the socket owner on success or 0 if the socket pointer - * inside sk_buff is NULL + * Return: uid of the socket owner on success or overflowuid if failed. */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ -- 2.1.2.532.g19b5d50
