[PATCH] cifs: fix GlobalMid_Lock bug in cifs_reconnect

[PATCH] cifs: fix GlobalMid_Lock bug in cifs_reconnect

[Ronnie Sahlberg]

We can not hold the GlobalMid_Lock spinlock during the
dfs processing in cifs_reconnect since it invokes things that may sleep
and thus trigger :

BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:23

Thus we need to drop the spinlock during this code block.

RHBZ: 1716743

Cc: stable@vger.kernel.org
Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
---
 fs/cifs/connect.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 8c4121da624e..8dd6637a3cbb 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -476,6 +476,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 	spin_lock(&GlobalMid_Lock);
 	server->nr_targets = 1;
 #ifdef CONFIG_CIFS_DFS_UPCALL
+	spin_unlock(&GlobalMid_Lock);
 	cifs_sb = find_super_by_tcp(server);
 	if (IS_ERR(cifs_sb)) {
 		rc = PTR_ERR(cifs_sb);
@@ -493,6 +494,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
 	}
 	cifs_dbg(FYI, "%s: will retry %d target(s)\n", __func__,
 		 server->nr_targets);
+	spin_lock(&GlobalMid_Lock);
 #endif
 	if (server->tcpStatus == CifsExiting) {
 		/* the demux thread will exit normally
-- 
2.13.6

Re: [PATCH] cifs: fix GlobalMid_Lock bug in cifs_reconnect

[Steve French]

tentatively merged into cifs-2.6.git for-next and to the github tree

On Thu, Jun 13, 2019 at 10:02 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
>
> We can not hold the GlobalMid_Lock spinlock during the
> dfs processing in cifs_reconnect since it invokes things that may sleep
> and thus trigger :
>
> BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:23
>
> Thus we need to drop the spinlock during this code block.
>
> RHBZ: 1716743
>
> Cc: stable@vger.kernel.org
> Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> ---
>  fs/cifs/connect.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> index 8c4121da624e..8dd6637a3cbb 100644
> --- a/fs/cifs/connect.c
> +++ b/fs/cifs/connect.c
> @@ -476,6 +476,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
>         spin_lock(&GlobalMid_Lock);
>         server->nr_targets = 1;
>  #ifdef CONFIG_CIFS_DFS_UPCALL
> +       spin_unlock(&GlobalMid_Lock);
>         cifs_sb = find_super_by_tcp(server);
>         if (IS_ERR(cifs_sb)) {
>                 rc = PTR_ERR(cifs_sb);
> @@ -493,6 +494,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
>         }
>         cifs_dbg(FYI, "%s: will retry %d target(s)\n", __func__,
>                  server->nr_targets);
> +       spin_lock(&GlobalMid_Lock);
>  #endif
>         if (server->tcpStatus == CifsExiting) {
>                 /* the demux thread will exit normally
> --
> 2.13.6
>


-- 
Thanks,

Steve

Re: [PATCH] cifs: fix GlobalMid_Lock bug in cifs_reconnect

[Pavel Shilovsky]

Acked-by: Pavel Shilovsky <pshilov@microsoft.com>

--
Best regards,
Pavel Shilovsky

чт, 13 июн. 2019 г. в 20:57, Steve French <smfrench@gmail.com>:
>
> tentatively merged into cifs-2.6.git for-next and to the github tree
>
> On Thu, Jun 13, 2019 at 10:02 PM Ronnie Sahlberg <lsahlber@redhat.com> wrote:
> >
> > We can not hold the GlobalMid_Lock spinlock during the
> > dfs processing in cifs_reconnect since it invokes things that may sleep
> > and thus trigger :
> >
> > BUG: sleeping function called from invalid context at kernel/locking/rwsem.c:23
> >
> > Thus we need to drop the spinlock during this code block.
> >
> > RHBZ: 1716743
> >
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Ronnie Sahlberg <lsahlber@redhat.com>
> > ---
> >  fs/cifs/connect.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
> > index 8c4121da624e..8dd6637a3cbb 100644
> > --- a/fs/cifs/connect.c
> > +++ b/fs/cifs/connect.c
> > @@ -476,6 +476,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
> >         spin_lock(&GlobalMid_Lock);
> >         server->nr_targets = 1;
> >  #ifdef CONFIG_CIFS_DFS_UPCALL
> > +       spin_unlock(&GlobalMid_Lock);
> >         cifs_sb = find_super_by_tcp(server);
> >         if (IS_ERR(cifs_sb)) {
> >                 rc = PTR_ERR(cifs_sb);
> > @@ -493,6 +494,7 @@ cifs_reconnect(struct TCP_Server_Info *server)
> >         }
> >         cifs_dbg(FYI, "%s: will retry %d target(s)\n", __func__,
> >                  server->nr_targets);
> > +       spin_lock(&GlobalMid_Lock);
> >  #endif
> >         if (server->tcpStatus == CifsExiting) {
> >                 /* the demux thread will exit normally
> > --
> > 2.13.6
> >
>
>
> --
> Thanks,
>
> Steve