| Message ID | 1503589796-24789-1-git-send-email-stefan.bader@canonical.com |
|---|---|
| State | New |
| Headers | show |
On 08/24/17 17:49, Stefan Bader wrote: > From 667526d7ccd320b438b81136af53fe2ab0f11013 Mon Sep 17 00:00:00 2001 > From: Eric Dumazet <edumazet@google.com> > Date: Tue, 14 Feb 2017 09:03:51 -0800 > Subject: [PATCH] packet: fix races in fanout_add() > > Multiple threads can call fanout_add() at the same time. > > We need to grab fanout_mutex earlier to avoid races that could > lead to one thread freeing po->rollover that was set by another thread. > > Do the same in fanout_release(), for peace of mind, and to help us > finding lockdep issues earlier. > > Fixes: dc99f600698d ("packet: Add fanout support.") > Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: Willem de Bruijn <willemb@google.com> > Signed-off-by: David S. Miller <davem@davemloft.net> > > CVE-2017-6346 > > (backported from commit d199fab63c11998a602205f7ee7ff7c05c97164b) > [smb: no po->rollover, verified against 3.2.y backport from bwh] > Signed-off-by: Stefan Bader <stefan.bader@canonical.com> > --- > Notes: > - was fixed in 4.10 and 4.4.52, so only Trusty left to fix > - in Trusty there is no po->rollover, so context had to be adjusted > to make up for that. > - The resulting changes look like the possible race window is much > smaller than for later kernels, but on the other hand it cannot > hurt to extend the mutex coverage by a bit. > > -Stefan > > net/packet/af_packet.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 146274a..59a1558 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -1315,13 +1315,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) > return -EINVAL; > } > > + mutex_lock(&fanout_mutex); > + > + err = -EINVAL; > if (!po->running) > - return -EINVAL; > + goto out; > > + err = -EALREADY; > if (po->fanout) > - return -EALREADY; > + goto out; > > - mutex_lock(&fanout_mutex); > match = NULL; > list_for_each_entry(f, &fanout_list, list) { > if (f->id == id && > @@ -1377,17 +1380,16 @@ static void fanout_release(struct sock *sk) > struct packet_sock *po = pkt_sk(sk); > struct packet_fanout *f; > > - f = po->fanout; > - if (!f) > - return; > - > mutex_lock(&fanout_mutex); > - po->fanout = NULL; > + f = po->fanout; > + if (f) { > + po->fanout = NULL; > > - if (atomic_dec_and_test(&f->sk_ref)) { > - list_del(&f->list); > - dev_remove_pack(&f->prot_hook); > - kfree(f); > + if (atomic_dec_and_test(&f->sk_ref)) { > + list_del(&f->list); > + dev_remove_pack(&f->prot_hook); > + kfree(f); > + } > } > mutex_unlock(&fanout_mutex); > } > Backport looks good to me. Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
On 24/08/17 16:49, Stefan Bader wrote: > From 667526d7ccd320b438b81136af53fe2ab0f11013 Mon Sep 17 00:00:00 2001 > From: Eric Dumazet <edumazet@google.com> > Date: Tue, 14 Feb 2017 09:03:51 -0800 > Subject: [PATCH] packet: fix races in fanout_add() > > Multiple threads can call fanout_add() at the same time. > > We need to grab fanout_mutex earlier to avoid races that could > lead to one thread freeing po->rollover that was set by another thread. > > Do the same in fanout_release(), for peace of mind, and to help us > finding lockdep issues earlier. > > Fixes: dc99f600698d ("packet: Add fanout support.") > Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: Willem de Bruijn <willemb@google.com> > Signed-off-by: David S. Miller <davem@davemloft.net> > > CVE-2017-6346 > > (backported from commit d199fab63c11998a602205f7ee7ff7c05c97164b) > [smb: no po->rollover, verified against 3.2.y backport from bwh] > Signed-off-by: Stefan Bader <stefan.bader@canonical.com> > --- > Notes: > - was fixed in 4.10 and 4.4.52, so only Trusty left to fix > - in Trusty there is no po->rollover, so context had to be adjusted > to make up for that. > - The resulting changes look like the possible race window is much > smaller than for later kernels, but on the other hand it cannot > hurt to extend the mutex coverage by a bit. > > -Stefan > > net/packet/af_packet.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 146274a..59a1558 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -1315,13 +1315,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) > return -EINVAL; > } > > + mutex_lock(&fanout_mutex); > + > + err = -EINVAL; > if (!po->running) > - return -EINVAL; > + goto out; > > + err = -EALREADY; > if (po->fanout) > - return -EALREADY; > + goto out; > > - mutex_lock(&fanout_mutex); > match = NULL; > list_for_each_entry(f, &fanout_list, list) { > if (f->id == id && > @@ -1377,17 +1380,16 @@ static void fanout_release(struct sock *sk) > struct packet_sock *po = pkt_sk(sk); > struct packet_fanout *f; > > - f = po->fanout; > - if (!f) > - return; > - > mutex_lock(&fanout_mutex); > - po->fanout = NULL; > + f = po->fanout; > + if (f) { > + po->fanout = NULL; > > - if (atomic_dec_and_test(&f->sk_ref)) { > - list_del(&f->list); > - dev_remove_pack(&f->prot_hook); > - kfree(f); > + if (atomic_dec_and_test(&f->sk_ref)) { > + list_del(&f->list); > + dev_remove_pack(&f->prot_hook); > + kfree(f); > + } > } > mutex_unlock(&fanout_mutex); > } > Thanks Stefan, I believe this is semantically the same as the upstream patch with respect to the locking. Looks good. Acked-by: Colin Ian King <colin.king@canonical.com>
Applied to trusty/master-next branch. Thanks.
On 24/08/17 16:49, Stefan Bader wrote: > From 667526d7ccd320b438b81136af53fe2ab0f11013 Mon Sep 17 00:00:00 2001 > From: Eric Dumazet <edumazet@google.com> > Date: Tue, 14 Feb 2017 09:03:51 -0800 > Subject: [PATCH] packet: fix races in fanout_add() > > Multiple threads can call fanout_add() at the same time. > > We need to grab fanout_mutex earlier to avoid races that could > lead to one thread freeing po->rollover that was set by another thread. > > Do the same in fanout_release(), for peace of mind, and to help us > finding lockdep issues earlier. > > Fixes: dc99f600698d ("packet: Add fanout support.") > Fixes: 0648ab70afe6 ("packet: rollover prepare: per-socket state") > Signed-off-by: Eric Dumazet <edumazet@google.com> > Cc: Willem de Bruijn <willemb@google.com> > Signed-off-by: David S. Miller <davem@davemloft.net> > > CVE-2017-6346 > > (backported from commit d199fab63c11998a602205f7ee7ff7c05c97164b) > [smb: no po->rollover, verified against 3.2.y backport from bwh] > Signed-off-by: Stefan Bader <stefan.bader@canonical.com> > --- > Notes: > - was fixed in 4.10 and 4.4.52, so only Trusty left to fix > - in Trusty there is no po->rollover, so context had to be adjusted > to make up for that. > - The resulting changes look like the possible race window is much > smaller than for later kernels, but on the other hand it cannot > hurt to extend the mutex coverage by a bit. > > -Stefan > > net/packet/af_packet.c | 26 ++++++++++++++------------ > 1 file changed, 14 insertions(+), 12 deletions(-) > > diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c > index 146274a..59a1558 100644 > --- a/net/packet/af_packet.c > +++ b/net/packet/af_packet.c > @@ -1315,13 +1315,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) > return -EINVAL; > } > > + mutex_lock(&fanout_mutex); > + > + err = -EINVAL; > if (!po->running) > - return -EINVAL; > + goto out; > > + err = -EALREADY; > if (po->fanout) > - return -EALREADY; > + goto out; > > - mutex_lock(&fanout_mutex); > match = NULL; > list_for_each_entry(f, &fanout_list, list) { > if (f->id == id && > @@ -1377,17 +1380,16 @@ static void fanout_release(struct sock *sk) > struct packet_sock *po = pkt_sk(sk); > struct packet_fanout *f; > > - f = po->fanout; > - if (!f) > - return; > - > mutex_lock(&fanout_mutex); > - po->fanout = NULL; > + f = po->fanout; > + if (f) { > + po->fanout = NULL; > > - if (atomic_dec_and_test(&f->sk_ref)) { > - list_del(&f->list); > - dev_remove_pack(&f->prot_hook); > - kfree(f); > + if (atomic_dec_and_test(&f->sk_ref)) { > + list_del(&f->list); > + dev_remove_pack(&f->prot_hook); > + kfree(f); > + } > } > mutex_unlock(&fanout_mutex); > } > I'm reasonably confident this backport looks sane. Good to know it compares well to the 3.2.y backport from bwh. Acked-by: Colin Ian King <colin.king@canonical.com>
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 146274a..59a1558 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -1315,13 +1315,16 @@ static int fanout_add(struct sock *sk, u16 id, u16 type_flags) return -EINVAL; } + mutex_lock(&fanout_mutex); + + err = -EINVAL; if (!po->running) - return -EINVAL; + goto out; + err = -EALREADY; if (po->fanout) - return -EALREADY; + goto out; - mutex_lock(&fanout_mutex); match = NULL; list_for_each_entry(f, &fanout_list, list) { if (f->id == id && @@ -1377,17 +1380,16 @@ static void fanout_release(struct sock *sk) struct packet_sock *po = pkt_sk(sk); struct packet_fanout *f; - f = po->fanout; - if (!f) - return; - mutex_lock(&fanout_mutex); - po->fanout = NULL; + f = po->fanout; + if (f) { + po->fanout = NULL; - if (atomic_dec_and_test(&f->sk_ref)) { - list_del(&f->list); - dev_remove_pack(&f->prot_hook); - kfree(f); + if (atomic_dec_and_test(&f->sk_ref)) { + list_del(&f->list); + dev_remove_pack(&f->prot_hook); + kfree(f); + } } mutex_unlock(&fanout_mutex); }