| Message ID | 1587361243-83431-1-git-send-email-xiyuyang19@fudan.edu.cn (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | ceph: Fix potential ceph_osd_request refcnt leak | expand |
On Mon, Apr 20, 2020 at 7:41 AM Xiyu Yang <xiyuyang19@fudan.edu.cn> wrote: > > ceph_writepages_start() invokes ceph_osdc_start_request(), which > increases the refcount of the ceph_osd_request object "req" and then > submit the request. > > When ceph_writepages_start() returns or a new object is assigned to > "req", the original local reference of "req" becomes invalid, so the > refcount should be decreased to keep refcount balanced. > > The reference counting issue happens in a normal path of > ceph_writepages_start(). Before NULL assigned to "req", the function > forgets to decrease its refcnt increased by ceph_osdc_start_request() > and will cause a refcnt leak. > > Fix this issue by calling ceph_osdc_put_request() before the original > object pointed by "req" becomes invalid. > > Fixes: 1d3576fd10f0 ("ceph: address space operations") > Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> > Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> > --- > fs/ceph/addr.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c > index 7ab616601141..b02c050a3418 100644 > --- a/fs/ceph/addr.c > +++ b/fs/ceph/addr.c > @@ -1126,6 +1126,7 @@ static int ceph_writepages_start(struct address_space *mapping, > req->r_mtime = inode->i_mtime; > rc = ceph_osdc_start_request(&fsc->client->osdc, req, true); > BUG_ON(rc); > + ceph_osdc_put_request(req); > req = NULL; > > wbc->nr_to_write -= i; Hi Xiyu, I think this reference is put in writepages_finish(). Putting it in ceph_writepages_start() will result in freed pointer dereference in libceph (in __complete_request() or elsewhere). Thanks, Ilya
diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c index 7ab616601141..b02c050a3418 100644 --- a/fs/ceph/addr.c +++ b/fs/ceph/addr.c @@ -1126,6 +1126,7 @@ static int ceph_writepages_start(struct address_space *mapping, req->r_mtime = inode->i_mtime; rc = ceph_osdc_start_request(&fsc->client->osdc, req, true); BUG_ON(rc); + ceph_osdc_put_request(req); req = NULL; wbc->nr_to_write -= i;
ceph_writepages_start() invokes ceph_osdc_start_request(), which increases the refcount of the ceph_osd_request object "req" and then submit the request. When ceph_writepages_start() returns or a new object is assigned to "req", the original local reference of "req" becomes invalid, so the refcount should be decreased to keep refcount balanced. The reference counting issue happens in a normal path of ceph_writepages_start(). Before NULL assigned to "req", the function forgets to decrease its refcnt increased by ceph_osdc_start_request() and will cause a refcnt leak. Fix this issue by calling ceph_osdc_put_request() before the original object pointed by "req" becomes invalid. Fixes: 1d3576fd10f0 ("ceph: address space operations") Signed-off-by: Xiyu Yang <xiyuyang19@fudan.edu.cn> Signed-off-by: Xin Tan <tanxin.ctf@gmail.com> --- fs/ceph/addr.c | 1 + 1 file changed, 1 insertion(+)