| Message ID | 1543310472-31861-1-git-send-email-bianpan2016@163.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [V2] libceph: fix use after free | expand |
On Tue, Nov 27, 2018 at 10:22 AM Pan Bian <bianpan2016@163.com> wrote: > > The function ceph_monc_handle_map calls kfree(old) to free the old > monitor map, old points to monc->monmap. However, after that, it reads > monc->monmap->epoch and passes it to __ceph_monc_got_map. This will > result in a use-after-free bug. The patch moves the free operation after > the call to __ceph_monc_got_map. > > Fixes: 82dcabad750 ("libceph: revamp subs code, switch to SUBSCRIBE2 protocol") > > Signed-off-by: Pan Bian <bianpan2016@163.com> > --- > V2: correct the format of the tag Fixes > --- > net/ceph/mon_client.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c > index 18deb3d..05ef5aa 100644 > --- a/net/ceph/mon_client.c > +++ b/net/ceph/mon_client.c > @@ -478,9 +478,10 @@ static void ceph_monc_handle_map(struct ceph_mon_client *monc, > } > > client->monc.monmap = monmap; monc->monmap is assigned here. It's not obvious, but monc->monmap and client->monc.monmap is the same pointer. > - kfree(old); > > __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap->epoch); ceph_monmap_decode() returns the new map, kfree() frees the old map. I don't see a use-after-free here. Thanks, Ilya
On Tue, Nov 27, 2018 at 11:17:26AM +0100, Ilya Dryomov wrote: > On Tue, Nov 27, 2018 at 10:22 AM Pan Bian <bianpan2016@163.com> wrote: > > > > The function ceph_monc_handle_map calls kfree(old) to free the old > > monitor map, old points to monc->monmap. However, after that, it reads > > monc->monmap->epoch and passes it to __ceph_monc_got_map. This will > > result in a use-after-free bug. The patch moves the free operation after > > the call to __ceph_monc_got_map. > > > > Fixes: 82dcabad750 ("libceph: revamp subs code, switch to SUBSCRIBE2 protocol") > > > > Signed-off-by: Pan Bian <bianpan2016@163.com> > > --- > > V2: correct the format of the tag Fixes > > --- > > net/ceph/mon_client.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c > > index 18deb3d..05ef5aa 100644 > > --- a/net/ceph/mon_client.c > > +++ b/net/ceph/mon_client.c > > @@ -478,9 +478,10 @@ static void ceph_monc_handle_map(struct ceph_mon_client *monc, > > } > > > > client->monc.monmap = monmap; > > monc->monmap is assigned here. It's not obvious, but monc->monmap and > client->monc.monmap is the same pointer. > > > - kfree(old); > > > > __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap->epoch); > > ceph_monmap_decode() returns the new map, kfree() frees the old map. > I don't see a use-after-free here. Got it. Thank you! Pan > > Thanks, > > Ilya
diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c index 18deb3d..05ef5aa 100644 --- a/net/ceph/mon_client.c +++ b/net/ceph/mon_client.c @@ -478,9 +478,10 @@ static void ceph_monc_handle_map(struct ceph_mon_client *monc, } client->monc.monmap = monmap; - kfree(old); __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap->epoch); + kfree(old); + client->have_fsid = true; out:
The function ceph_monc_handle_map calls kfree(old) to free the old monitor map, old points to monc->monmap. However, after that, it reads monc->monmap->epoch and passes it to __ceph_monc_got_map. This will result in a use-after-free bug. The patch moves the free operation after the call to __ceph_monc_got_map. Fixes: 82dcabad750 ("libceph: revamp subs code, switch to SUBSCRIBE2 protocol") Signed-off-by: Pan Bian <bianpan2016@163.com> --- V2: correct the format of the tag Fixes --- net/ceph/mon_client.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)