| Message ID | CAH2r5mtpx88bvKPDZs24ipxH+pm_82ug_w2QPKpB+9Z0xjAYiA@mail.gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | smb3: fix unmount hang in open_shroot | expand |
"Steve French" <smfrench@gmail.com> writes: > + /* > + * We do not hold the lock for the open because in case > + * SMB2_open needs to reconnect, it will end up calling > + * cifs_mark_open_files_invalid() which takes the lock again > + * thus causing a deadlock > + */ > + > + mutex_unlock(&tcon->crfid.fid_mutex); > + Good catch. Since the compounding changes it is SMB2_open_init() that is triggering the reconnect -> mark_open_files_invalid() code path so it looks good to me. Might be worth updating the comment to s/SMB2_open/SMB2_open_init/ before you commit. Reviewed-by: Aurelien Aptel <aaptel@suse.com> Cheers,
Aurélien Aptel <aaptel@suse.com> writes: > Good catch. Since the compounding changes it is SMB2_open_init() that is > triggering the reconnect -> mark_open_files_invalid() code path so it > looks good to me. Might be worth updating the comment to > s/SMB2_open/SMB2_open_init/ before you commit. Ah it seems you also need to make SMB2_open_init exit via the oshr_free label otherwise you the mutex gets unlocked twice (see Dan Carpenter automatic test email). This smatch tool is pretty nice... Cheers
Agree. Both SMB2_open_init and SMB2_query_info_init should exit through oshr_free to avoid double unlock. -- Best regards, Pavel Shilovsky пт, 13 сент. 2019 г. в 07:36, Aurélien Aptel <aaptel@suse.com>: > > Aurélien Aptel <aaptel@suse.com> writes: > > Good catch. Since the compounding changes it is SMB2_open_init() that is > > triggering the reconnect -> mark_open_files_invalid() code path so it > > looks good to me. Might be worth updating the comment to > > s/SMB2_open/SMB2_open_init/ before you commit. > > Ah it seems you also need to make SMB2_open_init exit via the oshr_free > label otherwise you the mutex gets unlocked twice (see Dan Carpenter > automatic test email). This smatch tool is pretty nice... > > Cheers > -- > Aurélien Aptel / SUSE Labs Samba Team > GPG: 1839 CB5F 9F5B FB9B AA97 8C99 03C8 A49B 521B D5D3 > SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE > GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
From 1f16bb0483a133882dc2f405dfcc26daa30b9117 Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 12 Sep 2019 17:52:54 -0500
Subject: [PATCH] smb3: fix unmount hang in open_shroot
An earlier patch "CIFS: fix deadlock in cached root handling"
did not completely address the deadlock in open_shroot. This
patch addresses the deadlock.
In testing the recent patch:
smb3: improve handling of share deleted (and share recreated)
we were able to reproduce the open_shroot deadlock to one
of the target servers in unmount in a delete share scenario.
Fixes: 7e5a70ad88b1e ("CIFS: fix deadlock in cached root handling")
Suggested-by: Pavel Shilovsky <pshilov@microsoft.com>
Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
CC: Aurelien Aptel <aaptel@suse.com>
CC: Stable <stable@vger.kernel.org>
---
fs/cifs/smb2ops.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 3672ce0bfbaf..150327ebb2b4 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -658,6 +658,15 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
return 0;
}
+ /*
+ * We do not hold the lock for the open because in case
+ * SMB2_open needs to reconnect, it will end up calling
+ * cifs_mark_open_files_invalid() which takes the lock again
+ * thus causing a deadlock
+ */
+
+ mutex_unlock(&tcon->crfid.fid_mutex);
+
if (smb3_encryption_required(tcon))
flags |= CIFS_TRANSFORM_REQ;
@@ -696,14 +705,6 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
smb2_set_related(&rqst[1]);
- /*
- * We do not hold the lock for the open because in case
- * SMB2_open needs to reconnect, it will end up calling
- * cifs_mark_open_files_invalid() which takes the lock again
- * thus causing a deadlock
- */
-
- mutex_unlock(&tcon->crfid.fid_mutex);
rc = compound_send_recv(xid, ses, flags, 2, rqst,
resp_buftype, rsp_iov);
mutex_lock(&tcon->crfid.fid_mutex);
--
2.20.1
smb3: fix unmount hang in open_shroot An earlier patch "CIFS: fix deadlock in cached root handling" did not completely address the deadlock in open_shroot. This patch addresses the deadlock. In testing the recent patch: smb3: improve handling of share deleted (and share recreated) we were able to reproduce the open_shroot deadlock to one of the target servers in unmount in a delete share scenario. Fixes: 7e5a70ad88b1e ("CIFS: fix deadlock in cached root handling") Suggested-by: Pavel Shilovsky <pshilov@microsoft.com> Reviewed-by: Pavel Shilovsky <pshilov@microsoft.com> Signed-off-by: Steve French <stfrench@microsoft.com> CC: Aurelien Aptel <aaptel@suse.com> CC: Stable <stable@vger.kernel.org> --- fs/cifs/smb2ops.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) @@ -696,14 +705,6 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid) smb2_set_related(&rqst[1]); - /* - * We do not hold the lock for the open because in case - * SMB2_open needs to reconnect, it will end up calling - * cifs_mark_open_files_invalid() which takes the lock again - * thus causing a deadlock - */ - - mutex_unlock(&tcon->crfid.fid_mutex); rc = compound_send_recv(xid, ses, flags, 2, rqst, resp_buftype, rsp_iov); mutex_lock(&tcon->crfid.fid_mutex); -- Thanks, Steve