3.16.40-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Willem de Bruijn <willemb@xxxxxxxxxx>
commit f4979fcea7fd36d8e2f556abef86f80e0d5af1ba upstream.
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: Willem de Bruijn <willemb@xxxxxxxxxx>
Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
include/linux/filter.h | 6 +++++-
net/core/filter.c | 10 +++++-----
net/rose/rose_in.c | 3 ++-
3 files changed, 12 insertions(+), 7 deletions(-)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -346,7 +346,11 @@ static inline unsigned int sk_filter_siz
#define sk_filter_proglen(fprog) \
(fprog->len * sizeof(fprog->filter[0]))
-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);
+}
void sk_filter_select_runtime(struct sk_filter *fp);
void sk_filter_free(struct sk_filter *fp);
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -94,9 +94,10 @@ static inline void *load_pointer(const s
}
/**
- * 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 filter code and then cut skb->data to correct size returned by
* sk_run_filter. If pkt_len is 0 we toss packet. If skb->len is smaller
@@ -105,7 +106,7 @@ static inline void *load_pointer(const s
* 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;
@@ -126,14 +127,13 @@ int sk_filter(struct sock *sk, struct sk
filter = rcu_dereference(sk->sk_filter);
if (filter) {
unsigned int pkt_len = SK_RUN_FILTER(filter, 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);
/* Base function for offset calculation. Needs to go into .text section,
* therefore keeping it non-static as well; will also be used by JITs
--- a/net/rose/rose_in.c
+++ b/net/rose/rose_in.c
@@ -164,7 +164,8 @@ static int rose_state3_machine(struct so
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 {