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packet: Move reference count in packet_sock to atomic_long_t

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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>
This commit is contained in:
Daniel Borkmann 2023-12-01 14:10:21 +01:00 committed by Jakub Kicinski
parent 79321a7939
commit db3fadacaf
2 changed files with 9 additions and 9 deletions
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16
net/packet/af_packet.c
View File

@ -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;

2
net/packet/internal.h
View File

@ -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;