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authorVincent Bernat <bernat@luffy.cx>2013-01-16 22:55:49 +0100
committerDavid S. Miller <davem@davemloft.net>2013-01-17 03:21:25 -0500
commitd59577b6ffd313d0ab3be39cb1ab47e29bdc9182 (patch)
tree8e3e40ac4fd723778af191af78e8f40519338709
parent5bd30d398792eb6351da2087fe81bbf755900991 (diff)
downloadlinux-linaro-stable-d59577b6ffd313d0ab3be39cb1ab47e29bdc9182.tar.gz
sk-filter: Add ability to lock a socket filter program
While a privileged program can open a raw socket, attach some restrictive filter and drop its privileges (or send the socket to an unprivileged program through some Unix socket), the filter can still be removed or modified by the unprivileged program. This commit adds a socket option to lock the filter (SO_LOCK_FILTER) preventing any modification of a socket filter program. This is similar to OpenBSD BIOCLOCK ioctl on bpf sockets, except even root is not allowed change/drop the filter. The state of the lock can be read with getsockopt(). No error is triggered if the state is not changed. -EPERM is returned when a user tries to remove the lock or to change/remove the filter while the lock is active. The check is done directly in sk_attach_filter() and sk_detach_filter() and does not affect only setsockopt() syscall. Signed-off-by: Vincent Bernat <bernat@luffy.cx> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--Documentation/networking/filter.txt11
-rw-r--r--arch/alpha/include/uapi/asm/socket.h1
-rw-r--r--arch/avr32/include/uapi/asm/socket.h2
-rw-r--r--arch/cris/include/uapi/asm/socket.h2
-rw-r--r--arch/frv/include/uapi/asm/socket.h2
-rw-r--r--arch/h8300/include/uapi/asm/socket.h2
-rw-r--r--arch/ia64/include/uapi/asm/socket.h2
-rw-r--r--arch/m32r/include/uapi/asm/socket.h2
-rw-r--r--arch/mips/include/uapi/asm/socket.h1
-rw-r--r--arch/mn10300/include/uapi/asm/socket.h2
-rw-r--r--arch/parisc/include/uapi/asm/socket.h1
-rw-r--r--arch/powerpc/include/uapi/asm/socket.h2
-rw-r--r--arch/s390/include/uapi/asm/socket.h2
-rw-r--r--arch/sparc/include/uapi/asm/socket.h1
-rw-r--r--arch/xtensa/include/uapi/asm/socket.h2
-rw-r--r--include/net/sock.h1
-rw-r--r--include/uapi/asm-generic/socket.h2
-rw-r--r--net/core/filter.c6
-rw-r--r--net/core/sock.c11
19 files changed, 53 insertions, 2 deletions
diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt
index bbf2005270b5..cdb3e40b9d14 100644
--- a/Documentation/networking/filter.txt
+++ b/Documentation/networking/filter.txt
@@ -17,12 +17,12 @@ creating filters.
LSF is much simpler than BPF. One does not have to worry about
devices or anything like that. You simply create your filter
-code, send it to the kernel via the SO_ATTACH_FILTER ioctl and
+code, send it to the kernel via the SO_ATTACH_FILTER option and
if your filter code passes the kernel check on it, you then
immediately begin filtering data on that socket.
You can also detach filters from your socket via the
-SO_DETACH_FILTER ioctl. This will probably not be used much
+SO_DETACH_FILTER option. This will probably not be used much
since when you close a socket that has a filter on it the
filter is automagically removed. The other less common case
may be adding a different filter on the same socket where you had another
@@ -31,12 +31,19 @@ the old one and placing your new one in its place, assuming your
filter has passed the checks, otherwise if it fails the old filter
will remain on that socket.
+SO_LOCK_FILTER option allows to lock the filter attached to a
+socket. Once set, a filter cannot be removed or changed. This allows
+one process to setup a socket, attach a filter, lock it then drop
+privileges and be assured that the filter will be kept until the
+socket is closed.
+
Examples
========
Ioctls-
setsockopt(sockfd, SOL_SOCKET, SO_ATTACH_FILTER, &Filter, sizeof(Filter));
setsockopt(sockfd, SOL_SOCKET, SO_DETACH_FILTER, &value, sizeof(value));
+setsockopt(sockfd, SOL_SOCKET, SO_LOCK_FILTER, &value, sizeof(value));
See the BSD bpf.4 manpage and the BSD Packet Filter paper written by
Steven McCanne and Van Jacobson of Lawrence Berkeley Laboratory.
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 097c1577735a..755702eefd9c 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -77,5 +77,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
#endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/avr32/include/uapi/asm/socket.h b/arch/avr32/include/uapi/asm/socket.h
index 486df68abeec..f3f38a0e2ef9 100644
--- a/arch/avr32/include/uapi/asm/socket.h
+++ b/arch/avr32/include/uapi/asm/socket.h
@@ -70,4 +70,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* __ASM_AVR32_SOCKET_H */
diff --git a/arch/cris/include/uapi/asm/socket.h b/arch/cris/include/uapi/asm/socket.h
index b681b043f6c8..406b5838defd 100644
--- a/arch/cris/include/uapi/asm/socket.h
+++ b/arch/cris/include/uapi/asm/socket.h
@@ -72,6 +72,8 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
index 871f89b7fbda..d8e1132a1ab6 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -70,5 +70,7 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/h8300/include/uapi/asm/socket.h b/arch/h8300/include/uapi/asm/socket.h
index 90a2e573c7e6..c8b87a828206 100644
--- a/arch/h8300/include/uapi/asm/socket.h
+++ b/arch/h8300/include/uapi/asm/socket.h
@@ -70,4 +70,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index 23d6759bb57b..f390896c3104 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -79,4 +79,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
index 5e7088a26726..6a895155e7a3 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -70,4 +70,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index 17307ab90474..9d11a7713923 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -90,5 +90,6 @@ To add: #define SO_REUSEPORT 0x0200 /* Allow local address and port reuse. */
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
#endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
index af5366bbfe62..ab702c40b30e 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -70,4 +70,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index d9ff4731253b..da2c8d3c209e 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -69,6 +69,7 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 0x4024
+#define SO_LOCK_FILTER 0x4025
/* O_NONBLOCK clashes with the bits used for socket types. Therefore we
* have to define SOCK_NONBLOCK to a different value here.
diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
index eb0b1864d400..e6ca31816cc9 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -77,4 +77,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index 436d07c23be8..9ce60b68f070 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -76,4 +76,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index c83a937ead00..fbbba57547d1 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -66,6 +66,7 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 0x0027
+#define SO_LOCK_FILTER 0x0028
/* Security levels - as per NRL IPv6 - don't actually do anything */
#define SO_SECURITY_AUTHENTICATION 0x5001
diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
index 38079be1cf1e..dbf316487b51 100644
--- a/arch/xtensa/include/uapi/asm/socket.h
+++ b/arch/xtensa/include/uapi/asm/socket.h
@@ -81,4 +81,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* _XTENSA_SOCKET_H */
diff --git a/include/net/sock.h b/include/net/sock.h
index 182ca99405ad..5a34e2f03657 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -664,6 +664,7 @@ enum sock_flags {
* Will use last 4 bytes of packet sent from
* user-space instead.
*/
+ SOCK_FILTER_LOCKED, /* Filter cannot be changed anymore */
};
static inline void sock_copy_flags(struct sock *nsk, struct sock *osk)
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 2d32d073a6f9..3f6a99201410 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -73,4 +73,6 @@
/* Instruct lower device to use last 4-bytes of skb data as FCS */
#define SO_NOFCS 43
+#define SO_LOCK_FILTER 44
+
#endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/net/core/filter.c b/net/core/filter.c
index 2ead2a9b1859..2e20b55a7830 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -721,6 +721,9 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk)
unsigned int fsize = sizeof(struct sock_filter) * fprog->len;
int err;
+ if (sock_flag(sk, SOCK_FILTER_LOCKED))
+ return -EPERM;
+
/* Make sure new filter is there and in the right amounts. */
if (fprog->filter == NULL)
return -EINVAL;
@@ -757,6 +760,9 @@ int sk_detach_filter(struct sock *sk)
int ret = -ENOENT;
struct sk_filter *filter;
+ if (sock_flag(sk, SOCK_FILTER_LOCKED))
+ return -EPERM;
+
filter = rcu_dereference_protected(sk->sk_filter,
sock_owned_by_user(sk));
if (filter) {
diff --git a/net/core/sock.c b/net/core/sock.c
index bc131d419683..8258fb741e9a 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -861,6 +861,13 @@ set_rcvbuf:
ret = sk_detach_filter(sk);
break;
+ case SO_LOCK_FILTER:
+ if (sock_flag(sk, SOCK_FILTER_LOCKED) && !valbool)
+ ret = -EPERM;
+ else
+ sock_valbool_flag(sk, SOCK_FILTER_LOCKED, valbool);
+ break;
+
case SO_PASSSEC:
if (valbool)
set_bit(SOCK_PASSSEC, &sock->flags);
@@ -1140,6 +1147,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
goto lenout;
+ case SO_LOCK_FILTER:
+ v.val = sock_flag(sk, SOCK_FILTER_LOCKED);
+ break;
+
default:
return -ENOPROTOOPT;
}