Commit e07b98d9 authored by David S. Miller's avatar David S. Miller

bpf: Add strict alignment flag for BPF_PROG_LOAD.

Add a new field, "prog_flags", and an initial flag value
BPF_F_STRICT_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: default avatarDavid S. Miller <davem@davemloft.net>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent c5fc9692
...@@ -90,6 +90,7 @@ struct bpf_verifier_env { ...@@ -90,6 +90,7 @@ struct bpf_verifier_env {
struct bpf_prog *prog; /* eBPF program being verified */ struct bpf_prog *prog; /* eBPF program being verified */
struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */ struct bpf_verifier_stack_elem *head; /* stack of verifier states to be processed */
int stack_size; /* number of states to be processed */ int stack_size; /* number of states to be processed */
bool strict_alignment; /* perform strict pointer alignment checks */
struct bpf_verifier_state cur_state; /* current verifier state */ struct bpf_verifier_state cur_state; /* current verifier state */
struct bpf_verifier_state_list **explored_states; /* search pruning optimization */ struct bpf_verifier_state_list **explored_states; /* search pruning optimization */
const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */ const struct bpf_ext_analyzer_ops *analyzer_ops; /* external analyzer ops */
......
...@@ -132,6 +132,13 @@ enum bpf_attach_type { ...@@ -132,6 +132,13 @@ enum bpf_attach_type {
*/ */
#define BPF_F_ALLOW_OVERRIDE (1U << 0) #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 #define BPF_PSEUDO_MAP_FD 1
/* flags for BPF_MAP_UPDATE_ELEM command */ /* flags for BPF_MAP_UPDATE_ELEM command */
...@@ -177,6 +184,7 @@ union bpf_attr { ...@@ -177,6 +184,7 @@ union bpf_attr {
__u32 log_size; /* size of user buffer */ __u32 log_size; /* size of user buffer */
__aligned_u64 log_buf; /* user supplied buffer */ __aligned_u64 log_buf; /* user supplied buffer */
__u32 kern_version; /* checked when prog_type=kprobe */ __u32 kern_version; /* checked when prog_type=kprobe */
__u32 prog_flags;
}; };
struct { /* anonymous struct used by BPF_OBJ_* commands */ struct { /* anonymous struct used by BPF_OBJ_* commands */
......
...@@ -783,7 +783,7 @@ struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type) ...@@ -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); EXPORT_SYMBOL_GPL(bpf_prog_get_type);
/* last field in 'union bpf_attr' used by this command */ /* 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) static int bpf_prog_load(union bpf_attr *attr)
{ {
...@@ -796,6 +796,9 @@ 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)) if (CHECK_ATTR(BPF_PROG_LOAD))
return -EINVAL; return -EINVAL;
if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
return -EINVAL;
/* copy eBPF program license from user space */ /* copy eBPF program license from user space */
if (strncpy_from_user(license, u64_to_user_ptr(attr->license), if (strncpy_from_user(license, u64_to_user_ptr(attr->license),
sizeof(license) - 1) < 0) sizeof(license) - 1) < 0)
......
...@@ -791,6 +791,7 @@ static bool is_pointer_value(struct bpf_verifier_env *env, int regno) ...@@ -791,6 +791,7 @@ static bool is_pointer_value(struct bpf_verifier_env *env, int regno)
static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg,
int off, int size, bool strict) int off, int size, bool strict)
{ {
int ip_align;
int reg_off; int reg_off;
/* Byte size accesses are always allowed. */ /* Byte size accesses are always allowed. */
...@@ -807,10 +808,14 @@ static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg, ...@@ -807,10 +808,14 @@ static int check_pkt_ptr_alignment(const struct bpf_reg_state *reg,
reg_off += reg->aux_off; reg_off += reg->aux_off;
} }
/* skb->data is NET_IP_ALIGN-ed */ /* skb->data is NET_IP_ALIGN-ed, but for strict alignment checking
if ((NET_IP_ALIGN + reg_off + off) % size != 0) { * 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", 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; return -EACCES;
} }
...@@ -828,10 +833,11 @@ static int check_val_ptr_alignment(const struct bpf_reg_state *reg, ...@@ -828,10 +833,11 @@ static int check_val_ptr_alignment(const struct bpf_reg_state *reg,
return 0; return 0;
} }
static int check_ptr_alignment(const struct bpf_reg_state *reg, static int check_ptr_alignment(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
int off, int size) int off, int size)
{ {
bool strict = false; bool strict = env->strict_alignment;
if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)) if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
strict = true; strict = true;
...@@ -873,7 +879,7 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off, ...@@ -873,7 +879,7 @@ static int check_mem_access(struct bpf_verifier_env *env, u32 regno, int off,
if (size < 0) if (size < 0)
return size; return size;
err = check_ptr_alignment(reg, off, size); err = check_ptr_alignment(env, reg, off, size);
if (err) if (err)
return err; return err;
...@@ -3568,6 +3574,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) ...@@ -3568,6 +3574,10 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
} else { } else {
log_level = 0; log_level = 0;
} }
if (attr->prog_flags & BPF_F_STRICT_ALIGNMENT)
env->strict_alignment = true;
else
env->strict_alignment = false;
ret = replace_map_fd_with_map_ptr(env); ret = replace_map_fd_with_map_ptr(env);
if (ret < 0) if (ret < 0)
...@@ -3673,6 +3683,7 @@ int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops, ...@@ -3673,6 +3683,7 @@ int bpf_analyzer(struct bpf_prog *prog, const struct bpf_ext_analyzer_ops *ops,
mutex_lock(&bpf_verifier_lock); mutex_lock(&bpf_verifier_lock);
log_level = 0; log_level = 0;
env->strict_alignment = false;
env->explored_states = kcalloc(env->prog->len, env->explored_states = kcalloc(env->prog->len,
sizeof(struct bpf_verifier_state_list *), sizeof(struct bpf_verifier_state_list *),
......
...@@ -29,6 +29,7 @@ int main(void) ...@@ -29,6 +29,7 @@ int main(void)
attr.log_size = 0; attr.log_size = 0;
attr.log_level = 0; attr.log_level = 0;
attr.kern_version = 0; attr.kern_version = 0;
attr.prog_flags = 0;
/* /*
* Test existence of __NR_bpf and BPF_PROG_LOAD. * Test existence of __NR_bpf and BPF_PROG_LOAD.
......
...@@ -132,6 +132,13 @@ enum bpf_attach_type { ...@@ -132,6 +132,13 @@ enum bpf_attach_type {
*/ */
#define BPF_F_ALLOW_OVERRIDE (1U << 0) #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 #define BPF_PSEUDO_MAP_FD 1
/* flags for BPF_MAP_UPDATE_ELEM command */ /* flags for BPF_MAP_UPDATE_ELEM command */
...@@ -177,6 +184,7 @@ union bpf_attr { ...@@ -177,6 +184,7 @@ union bpf_attr {
__u32 log_size; /* size of user buffer */ __u32 log_size; /* size of user buffer */
__aligned_u64 log_buf; /* user supplied buffer */ __aligned_u64 log_buf; /* user supplied buffer */
__u32 kern_version; /* checked when prog_type=kprobe */ __u32 kern_version; /* checked when prog_type=kprobe */
__u32 prog_flags;
}; };
struct { /* anonymous struct used by BPF_OBJ_* commands */ struct { /* anonymous struct used by BPF_OBJ_* commands */
...@@ -481,8 +489,7 @@ union bpf_attr { ...@@ -481,8 +489,7 @@ union bpf_attr {
* u32 bpf_get_socket_uid(skb) * u32 bpf_get_socket_uid(skb)
* Get the owner uid of the socket stored inside sk_buff. * Get the owner uid of the socket stored inside sk_buff.
* @skb: pointer to skb * @skb: pointer to skb
* Return: uid of the socket owner on success or 0 if the socket pointer * Return: uid of the socket owner on success or overflowuid if failed.
* inside sk_buff is NULL
*/ */
#define __BPF_FUNC_MAPPER(FN) \ #define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \ FN(unspec), \
......
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