3.2.85-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 3.2: 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 @@ -150,7 +150,11 @@ static inline unsigned int sk_filter_len return fp->len * sizeof(struct sock_filter) + sizeof(*fp); } -extern 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); +} extern unsigned int sk_run_filter(const struct sk_buff *skb, const struct sock_filter *filter); extern int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk); --- a/net/core/filter.c +++ b/net/core/filter.c @@ -64,9 +64,10 @@ 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 @@ -75,7 +76,7 @@ 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; @@ -88,14 +89,13 @@ 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); /** * sk_run_filter - run a filter on a socket --- a/net/rose/rose_in.c +++ b/net/rose/rose_in.c @@ -165,7 +165,8 @@ 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 {