Hello Neil, Hello Trond, On Do, Sep 08, 2022 at 01:09:29 +0000, Trond Myklebust wrote: > On Thu, 2022-09-08 at 10:58 +1000, NeilBrown wrote: > > On Thu, 08 Sep 2022, Eugeniu Rosca wrote: > > > Hello all, > > > > > > On Mo, Apr 18, 2022 at 02:10:03 +0200, Greg Kroah-Hartman wrote: > > > > From: NeilBrown <neilb@xxxxxxx> > > > > > > > > commit 3848e96edf4788f772d83990022fa7023a233d83 upstream. > > > > > > > > xprt_destory() claims XPRT_LOCKED and then calls > > > > del_timer_sync(). > > > > Both xprt_unlock_connect() and xprt_release() call > > > > ->release_xprt() > > > > which drops XPRT_LOCKED and *then* xprt_schedule_autodisconnect() > > > > which calls mod_timer(). > > > > > > > > This may result in mod_timer() being called *after* > > > > del_timer_sync(). > > > > When this happens, the timer may fire long after the xprt has > > > > been freed, > > > > and run_timer_softirq() will probably crash. > > > > > > > > The pairing of ->release_xprt() and > > > > xprt_schedule_autodisconnect() is > > > > always called under ->transport_lock. So if we take - > > > > >transport_lock to > > > > call del_timer_sync(), we can be sure that mod_timer() will run > > > > first > > > > (if it runs at all). > > > > > > > > Cc: stable@xxxxxxxxxxxxxxx > > > > Signed-off-by: NeilBrown <neilb@xxxxxxx> > > > > Signed-off-by: Trond Myklebust <https://urldefense.proofpoint.com/v2/url?u=http-3A__trond.myklebust-40hammerspace.com&d=DwIGaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=SAhjP5GOmrADp1v_EE5jWoSuMlYCIt9gKduw-DCBPLs&m=HrAc1Ouz3sNPrdBv5QBgh7SToNI8M0iGJyDPgOTT5AE&s=cNzW7c7t83SH27ck7hxvneR9awrt17JualiCD6TZtdI&e=> > > > > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > > > > --- > > > > net/sunrpc/xprt.c | 7 +++++++ > > > > 1 file changed, 7 insertions(+) > > > > > > > > --- a/net/sunrpc/xprt.c > > > > +++ b/net/sunrpc/xprt.c > > > > @@ -1520,7 +1520,14 @@ static void xprt_destroy(struct rpc_xprt > > > > */ > > > > wait_on_bit_lock(&xprt->state, XPRT_LOCKED, > > > > TASK_UNINTERRUPTIBLE); > > > > > > > > + /* > > > > + * xprt_schedule_autodisconnect() can run after > > > > XPRT_LOCKED > > > > + * is cleared. We use ->transport_lock to ensure the > > > > mod_timer() > > > > + * can only run *before* del_time_sync(), never after. > > > > + */ > > > > + spin_lock(&xprt->transport_lock); > > > > del_timer_sync(&xprt->timer); > > > > + spin_unlock(&xprt->transport_lock); > > > > I think it is sufficient to change the to spin_{,un}lock_bh() > > in older kernels. The spinlock call need to match other uses of the > > same lock. > > Agreed. On older kernels, the xprt->transport_lock served the same > purpose, but it had to take a bh-safe spinlock in order to avoid > certain races with the socket callbacks. Since then, a number of > changes to both the socket layer and the SUNRPC code have made it > possible to eliminate bh-safe requirement. > > > > > Can you confirm doing that removes the problem? Your proposal [*] seems to resolve the issue for me. Any chance to get a stable patch, to which I will gladly provide the Reviewed-by/Tested-by signatures? > > > > NeilBrown > > [*] diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c index e7d55d63d4f1..7f9b94acf597 100644 --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1525,9 +1525,9 @@ static void xprt_destroy(struct rpc_xprt *xprt) * is cleared. We use ->transport_lock to ensure the mod_timer() * can only run *before* del_time_sync(), never after. */ - spin_lock(&xprt->transport_lock); + spin_lock_bh(&xprt->transport_lock); del_timer_sync(&xprt->timer); - spin_unlock(&xprt->transport_lock); + spin_unlock_bh(&xprt->transport_lock); /* * Destroy sockets etc from the system workqueue so they can Best Regards, Eugeniu Rosca
