Commit f4979fce authored by Willem de Bruijn's avatar Willem de Bruijn Committed by David S. Miller
Browse files

rose: limit sk_filter trim to payload 



Sockets can have a filter program attached that drops or trims
incoming packets based on the filter program return value.

Rose requires data packets to have at least ROSE_MIN_LEN bytes. It
verifies this on arrival in rose_route_frame and unconditionally pulls
the bytes in rose_recvmsg. The filter can trim packets to below this
value in-between, causing pull to fail, leaving the partial header at
the time of skb_copy_datagram_msg.

Place a lower bound on the size to which sk_filter may trim packets
by introducing sk_filter_trim_cap and call this for rose packets.

Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 22cb99fb

include/linux/filter.h

+5 −1
Original line number Diff line number Diff line
@@ -467,7 +467,11 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp) 
}

#endif /* CONFIG_DEBUG_SET_MODULE_RONX */



int sk_filter(struct sock *sk, struct sk_buff *skb);

int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);

static inline int sk_filter(struct sock *sk, struct sk_buff *skb)

{

	return sk_filter_trim_cap(sk, skb, 1);

}



struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err);

void bpf_prog_free(struct bpf_prog *fp);

net/core/filter.c

+5 −5
Original line number Diff line number Diff line
@@ -53,9 +53,10 @@ 
#include <net/sock_reuseport.h>



/**

 *	sk_filter - run a packet through a socket filter

 *	sk_filter_trim_cap - run a packet through a socket filter

 *	@sk: sock associated with &sk_buff

 *	@skb: buffer to filter

 *	@cap: limit on how short the eBPF program may trim the packet

 *

 * Run the eBPF program and then cut skb->data to correct size returned by

 * the program. If pkt_len is 0 we toss packet. If skb->len is smaller
@@ -64,7 +65,7 @@ 
 * be accepted or -EPERM if the packet should be tossed.

 *

 */

int sk_filter(struct sock *sk, struct sk_buff *skb)

int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap)

{

	int err;

	struct sk_filter *filter;
@@ -85,14 +86,13 @@ int sk_filter(struct sock *sk, struct sk_buff *skb) 
	filter = rcu_dereference(sk->sk_filter);

	if (filter) {

		unsigned int pkt_len = bpf_prog_run_save_cb(filter->prog, skb);



		err = pkt_len ? pskb_trim(skb, pkt_len) : -EPERM;

		err = pkt_len ? pskb_trim(skb, max(cap, pkt_len)) : -EPERM;

	}

	rcu_read_unlock();



	return err;

}

EXPORT_SYMBOL(sk_filter);

EXPORT_SYMBOL(sk_filter_trim_cap);



static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

net/rose/rose_in.c

+2 −1
Original line number Diff line number Diff line
@@ -164,7 +164,8 @@ static int rose_state3_machine(struct sock *sk, struct sk_buff *skb, int framety 
		rose_frames_acked(sk, nr);

		if (ns == rose->vr) {

			rose_start_idletimer(sk);

			if (sock_queue_rcv_skb(sk, skb) == 0) {

			if (sk_filter_trim_cap(sk, skb, ROSE_MIN_LEN) == 0 &&

			    __sock_queue_rcv_skb(sk, skb) == 0) {

				rose->vr = (rose->vr + 1) % ROSE_MODULUS;

				queued = 1;

			} else {

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