packet: Move reference count in packet_sock to atomic_long_t

commit db3fadacaf0c817b222090290d06ca2a338422d0 upstream.

In some potential instances the reference count on struct packet_sock
could be saturated and cause overflows which gets the kernel a bit
confused. To prevent this, move to a 64-bit atomic reference count on
64-bit architectures to prevent the possibility of this type to overflow.

Because we can not handle saturation, using refcount_t is not possible
in this place. Maybe someday in the future if it changes it could be
used. Also, instead of using plain atomic64_t, use atomic_long_t instead.
32-bit machines tend to be memory-limited (i.e. anything that increases
a reference uses so much memory that you can't actually get to 2**32
references). 32-bit architectures also tend to have serious problems
with 64-bit atomics. Hence, atomic_long_t is the more natural solution.

Reported-by: "The UK's National Cyber Security Centre (NCSC)" <security@ncsc.gov.uk>
Co-developed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@kernel.org
Reviewed-by: Willem de Bruijn <willemb@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231201131021.19999-1-daniel@iogearbox.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index a84e00b..7adf485 100644 (file)
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -4300,7 +4300,7 @@ static void packet_mm_open(struct vm_area_struct *vma)
        struct sock *sk = sock->sk;
 
        if (sk)
-               atomic_inc(&pkt_sk(sk)->mapped);
+               atomic_long_inc(&pkt_sk(sk)->mapped);
 }
 
 static void packet_mm_close(struct vm_area_struct *vma)
@@ -4310,7 +4310,7 @@ static void packet_mm_close(struct vm_area_struct *vma)
        struct sock *sk = sock->sk;
 
        if (sk)
-               atomic_dec(&pkt_sk(sk)->mapped);
+               atomic_long_dec(&pkt_sk(sk)->mapped);
 }
 
 static const struct vm_operations_struct packet_mmap_ops = {
@@ -4405,7 +4405,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 
        err = -EBUSY;
        if (!closing) {
-               if (atomic_read(&po->mapped))
+               if (atomic_long_read(&po->mapped))
                        goto out;
                if (packet_read_pending(rb))
                        goto out;
@@ -4508,7 +4508,7 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
 
        err = -EBUSY;
        mutex_lock(&po->pg_vec_lock);
-       if (closing || atomic_read(&po->mapped) == 0) {
+       if (closing || atomic_long_read(&po->mapped) == 0) {
                err = 0;
                spin_lock_bh(&rb_queue->lock);
                swap(rb->pg_vec, pg_vec);
@@ -4526,9 +4526,9 @@ static int packet_set_ring(struct sock *sk, union tpacket_req_u *req_u,
                po->prot_hook.func = (po->rx_ring.pg_vec) ?
                                                tpacket_rcv : packet_rcv;
                skb_queue_purge(rb_queue);
-               if (atomic_read(&po->mapped))
-                       pr_err("packet_mmap: vma is busy: %d\n",
-                              atomic_read(&po->mapped));
+               if (atomic_long_read(&po->mapped))
+                       pr_err("packet_mmap: vma is busy: %ld\n",
+                              atomic_long_read(&po->mapped));
        }
        mutex_unlock(&po->pg_vec_lock);
 
@@ -4606,7 +4606,7 @@ static int packet_mmap(struct file *file, struct socket *sock,
                }
        }
 
-       atomic_inc(&po->mapped);
+       atomic_long_inc(&po->mapped);
        vma->vm_ops = &packet_mmap_ops;
        err = 0;
 

diff --git a/net/packet/internal.h b/net/packet/internal.h
index 63f4865..11ba8a7 100644 (file)
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -122,7 +122,7 @@ struct packet_sock {
        __be16                  num;
        struct packet_rollover  *rollover;
        struct packet_mclist    *mclist;
-       atomic_t                mapped;
+       atomic_long_t           mapped;
        enum tpacket_versions   tp_version;
        unsigned int            tp_hdrlen;
        unsigned int            tp_reserve;