| Message ID | 20241007213502.28183-6-ignat@cloudflare.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | do not leave dangling sk pointers in pf->create functions | expand |
Hi Ignat, Thanks for the patch. On Tue. 8 Oct. 2024 at 06:37, Ignat Korchagin <ignat@cloudflare.com> wrote: > On error can_create() frees the allocated sk object, but sock_init_data() > has already attached it to the provided sock object. This will leave a > dangling sk pointer in the sock object and may cause use-after-free later. I was about to suggest that this should be backported to stable, but after reading the cover letter, I now understand that this patch is more an improvement to avoid false positives on kmemleak & Cie. Maybe the description could be a bit more nuanced? After patch 1/8 of this series, it seems that the use-after-free is not possible anymore. > Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> See above comment as notwithstanding. This said: Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> > --- > net/can/af_can.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/net/can/af_can.c b/net/can/af_can.c > index 707576eeeb58..01f3fbb3b67d 100644 > --- a/net/can/af_can.c > +++ b/net/can/af_can.c > @@ -171,6 +171,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol, > /* release sk on errors */ > sock_orphan(sk); > sock_put(sk); > + sock->sk = NULL; > } > > errout: > -- > 2.39.5 > >
On Tue, Oct 8, 2024 at 3:38 AM Vincent MAILHOL <mailhol.vincent@wanadoo.fr> wrote: > > Hi Ignat, > > Thanks for the patch. > > On Tue. 8 Oct. 2024 at 06:37, Ignat Korchagin <ignat@cloudflare.com> wrote: > > On error can_create() frees the allocated sk object, but sock_init_data() > > has already attached it to the provided sock object. This will leave a > > dangling sk pointer in the sock object and may cause use-after-free later. > > I was about to suggest that this should be backported to stable, but > after reading the cover letter, I now understand that this patch is > more an improvement to avoid false positives on kmemleak & Cie. Maybe > the description could be a bit more nuanced? After patch 1/8 of this > series, it seems that the use-after-free is not possible anymore. If we go with Kuniyuki's suggestion in the cover email to replace the explicit NULL with DEBUG_NET_WARN_ON_ONCE(sock->sk) in __sock_create() then use-after-free would be possible again except we will easily catch it. But I will review the description, when I respin the patches to net-next as requested by Jakub. > > Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> > > See above comment as notwithstanding. This said: > > Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr> Thank you. > > > --- > > net/can/af_can.c | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/net/can/af_can.c b/net/can/af_can.c > > index 707576eeeb58..01f3fbb3b67d 100644 > > --- a/net/can/af_can.c > > +++ b/net/can/af_can.c > > @@ -171,6 +171,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol, > > /* release sk on errors */ > > sock_orphan(sk); > > sock_put(sk); > > + sock->sk = NULL; > > } > > > > errout: > > -- > > 2.39.5 > > > >
diff --git a/net/can/af_can.c b/net/can/af_can.c index 707576eeeb58..01f3fbb3b67d 100644 --- a/net/can/af_can.c +++ b/net/can/af_can.c @@ -171,6 +171,7 @@ static int can_create(struct net *net, struct socket *sock, int protocol, /* release sk on errors */ sock_orphan(sk); sock_put(sk); + sock->sk = NULL; } errout:
On error can_create() frees the allocated sk object, but sock_init_data() has already attached it to the provided sock object. This will leave a dangling sk pointer in the sock object and may cause use-after-free later. Signed-off-by: Ignat Korchagin <ignat@cloudflare.com> --- net/can/af_can.c | 1 + 1 file changed, 1 insertion(+)