Commit a8fc9277 authored by Pavel Emelyanov's avatar Pavel Emelyanov Committed by David S. Miller

sk-filter: Add ability to get socket filter program (v2)

The SO_ATTACH_FILTER option is set only. I propose to add the get
ability by using SO_ATTACH_FILTER in getsockopt. To be less
irritating to eyes the SO_GET_FILTER alias to it is declared. This
ability is required by checkpoint-restore project to be able to
save full state of a socket.

There are two issues with getting filter back.

First, kernel modifies the sock_filter->code on filter load, thus in
order to return the filter element back to user we have to decode it
into user-visible constants. Fortunately the modification in question
is interconvertible.

Second, the BPF_S_ALU_DIV_K code modifies the command argument k to
speed up the run-time division by doing kernel_k = reciprocal(user_k).
Bad news is that different user_k may result in same kernel_k, so we
can't get the original user_k back. Good news is that we don't have
to do it. What we need to is calculate a user2_k so, that

  reciprocal(user2_k) == reciprocal(user_k) == kernel_k

i.e. if it's re-loaded back the compiled again value will be exactly
the same as it was. That said, the user2_k can be calculated like this

  user2_k = reciprocal(kernel_k)

with an exception, that if kernel_k == 0, then user2_k == 1.

The optlen argument is treated like this -- when zero, kernel returns
the amount of sock_fprog elements in filter, otherwise it should be
large enough for the sock_fprog array.

changes since v1:
* Declared SO_GET_FILTER in all arch headers
* Added decode of vlan-tag codes
Signed-off-by: default avatarPavel Emelyanov <xemul@parallels.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 96442e42
......@@ -47,6 +47,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -42,6 +42,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -49,6 +49,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -63,6 +63,7 @@ To add: #define SO_REUSEPORT 0x0200 /* Allow local address and port reuse. */
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -40,6 +40,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -48,6 +48,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 0x401a
#define SO_DETACH_FILTER 0x401b
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_ACCEPTCONN 0x401c
......
......@@ -47,6 +47,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -46,6 +46,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -41,6 +41,7 @@
#define SO_ATTACH_FILTER 0x001a
#define SO_DETACH_FILTER 0x001b
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 0x001c
#define SO_TIMESTAMP 0x001d
......
......@@ -52,6 +52,7 @@
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -45,6 +45,7 @@ extern void sk_unattached_filter_destroy(struct sk_filter *fp);
extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk);
extern int sk_detach_filter(struct sock *sk);
extern int sk_chk_filter(struct sock_filter *filter, unsigned int flen);
extern int sk_get_filter(struct sock *sk, struct sock_filter __user *filter, unsigned len);
#ifdef CONFIG_BPF_JIT
extern void bpf_jit_compile(struct sk_filter *fp);
......
......@@ -43,6 +43,7 @@
/* Socket filtering */
#define SO_ATTACH_FILTER 26
#define SO_DETACH_FILTER 27
#define SO_GET_FILTER SO_ATTACH_FILTER
#define SO_PEERNAME 28
#define SO_TIMESTAMP 29
......
......@@ -760,3 +760,133 @@ int sk_detach_filter(struct sock *sk)
return ret;
}
EXPORT_SYMBOL_GPL(sk_detach_filter);
static void sk_decode_filter(struct sock_filter *filt, struct sock_filter *to)
{
static const u16 decodes[] = {
[BPF_S_ALU_ADD_K] = BPF_ALU|BPF_ADD|BPF_K,
[BPF_S_ALU_ADD_X] = BPF_ALU|BPF_ADD|BPF_X,
[BPF_S_ALU_SUB_K] = BPF_ALU|BPF_SUB|BPF_K,
[BPF_S_ALU_SUB_X] = BPF_ALU|BPF_SUB|BPF_X,
[BPF_S_ALU_MUL_K] = BPF_ALU|BPF_MUL|BPF_K,
[BPF_S_ALU_MUL_X] = BPF_ALU|BPF_MUL|BPF_X,
[BPF_S_ALU_DIV_X] = BPF_ALU|BPF_DIV|BPF_X,
[BPF_S_ALU_MOD_K] = BPF_ALU|BPF_MOD|BPF_K,
[BPF_S_ALU_MOD_X] = BPF_ALU|BPF_MOD|BPF_X,
[BPF_S_ALU_AND_K] = BPF_ALU|BPF_AND|BPF_K,
[BPF_S_ALU_AND_X] = BPF_ALU|BPF_AND|BPF_X,
[BPF_S_ALU_OR_K] = BPF_ALU|BPF_OR|BPF_K,
[BPF_S_ALU_OR_X] = BPF_ALU|BPF_OR|BPF_X,
[BPF_S_ALU_XOR_K] = BPF_ALU|BPF_XOR|BPF_K,
[BPF_S_ALU_XOR_X] = BPF_ALU|BPF_XOR|BPF_X,
[BPF_S_ALU_LSH_K] = BPF_ALU|BPF_LSH|BPF_K,
[BPF_S_ALU_LSH_X] = BPF_ALU|BPF_LSH|BPF_X,
[BPF_S_ALU_RSH_K] = BPF_ALU|BPF_RSH|BPF_K,
[BPF_S_ALU_RSH_X] = BPF_ALU|BPF_RSH|BPF_X,
[BPF_S_ALU_NEG] = BPF_ALU|BPF_NEG,
[BPF_S_LD_W_ABS] = BPF_LD|BPF_W|BPF_ABS,
[BPF_S_LD_H_ABS] = BPF_LD|BPF_H|BPF_ABS,
[BPF_S_LD_B_ABS] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_PROTOCOL] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_PKTTYPE] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_IFINDEX] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_NLATTR] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_NLATTR_NEST] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_MARK] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_QUEUE] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_HATYPE] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_RXHASH] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_CPU] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_ALU_XOR_X] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_SECCOMP_LD_W] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_VLAN_TAG] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_ANC_VLAN_TAG_PRESENT] = BPF_LD|BPF_B|BPF_ABS,
[BPF_S_LD_W_LEN] = BPF_LD|BPF_W|BPF_LEN,
[BPF_S_LD_W_IND] = BPF_LD|BPF_W|BPF_IND,
[BPF_S_LD_H_IND] = BPF_LD|BPF_H|BPF_IND,
[BPF_S_LD_B_IND] = BPF_LD|BPF_B|BPF_IND,
[BPF_S_LD_IMM] = BPF_LD|BPF_IMM,
[BPF_S_LDX_W_LEN] = BPF_LDX|BPF_W|BPF_LEN,
[BPF_S_LDX_B_MSH] = BPF_LDX|BPF_B|BPF_MSH,
[BPF_S_LDX_IMM] = BPF_LDX|BPF_IMM,
[BPF_S_MISC_TAX] = BPF_MISC|BPF_TAX,
[BPF_S_MISC_TXA] = BPF_MISC|BPF_TXA,
[BPF_S_RET_K] = BPF_RET|BPF_K,
[BPF_S_RET_A] = BPF_RET|BPF_A,
[BPF_S_ALU_DIV_K] = BPF_ALU|BPF_DIV|BPF_K,
[BPF_S_LD_MEM] = BPF_LD|BPF_MEM,
[BPF_S_LDX_MEM] = BPF_LDX|BPF_MEM,
[BPF_S_ST] = BPF_ST,
[BPF_S_STX] = BPF_STX,
[BPF_S_JMP_JA] = BPF_JMP|BPF_JA,
[BPF_S_JMP_JEQ_K] = BPF_JMP|BPF_JEQ|BPF_K,
[BPF_S_JMP_JEQ_X] = BPF_JMP|BPF_JEQ|BPF_X,
[BPF_S_JMP_JGE_K] = BPF_JMP|BPF_JGE|BPF_K,
[BPF_S_JMP_JGE_X] = BPF_JMP|BPF_JGE|BPF_X,
[BPF_S_JMP_JGT_K] = BPF_JMP|BPF_JGT|BPF_K,
[BPF_S_JMP_JGT_X] = BPF_JMP|BPF_JGT|BPF_X,
[BPF_S_JMP_JSET_K] = BPF_JMP|BPF_JSET|BPF_K,
[BPF_S_JMP_JSET_X] = BPF_JMP|BPF_JSET|BPF_X,
};
u16 code;
code = filt->code;
to->code = decodes[code];
to->jt = filt->jt;
to->jf = filt->jf;
if (code == BPF_S_ALU_DIV_K) {
/*
* When loaded this rule user gave us X, which was
* translated into R = r(X). Now we calculate the
* RR = r(R) and report it back. If next time this
* value is loaded and RRR = r(RR) is calculated
* then the R == RRR will be true.
*
* One exception. X == 1 translates into R == 0 and
* we can't calculate RR out of it with r().
*/
if (filt->k == 0)
to->k = 1;
else
to->k = reciprocal_value(filt->k);
BUG_ON(reciprocal_value(to->k) != filt->k);
} else
to->k = filt->k;
}
int sk_get_filter(struct sock *sk, struct sock_filter __user *ubuf, unsigned int len)
{
struct sk_filter *filter;
int i, ret;
lock_sock(sk);
filter = rcu_dereference_protected(sk->sk_filter,
sock_owned_by_user(sk));
ret = 0;
if (!filter)
goto out;
ret = filter->len;
if (!len)
goto out;
ret = -EINVAL;
if (len < filter->len)
goto out;
ret = -EFAULT;
for (i = 0; i < filter->len; i++) {
struct sock_filter fb;
sk_decode_filter(&filter->insns[i], &fb);
if (copy_to_user(&ubuf[i], &fb, sizeof(fb)))
goto out;
}
ret = filter->len;
out:
release_sock(sk);
return ret;
}
......@@ -1077,6 +1077,12 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
case SO_BINDTODEVICE:
v.val = sk->sk_bound_dev_if;
break;
case SO_GET_FILTER:
len = sk_get_filter(sk, (struct sock_filter __user *)optval, len);
if (len < 0)
return len;
goto lenout;
default:
return -ENOPROTOOPT;
}
......
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