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SubjectRE: [PATCH 5.2 02/45] smb3: fix unmount hang in open_shroot
Date
Hi Greg,

Are you going to apply this patch to the 5.3.y stable kernel? The patch is applicable there too.

Best regards,
Pavel Shilovsky

-----Original Message-----
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Sent: Sunday, September 29, 2019 6:56 AM
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>; stable@vger.kernel.org; kbuild test robot <lkp@intel.com>; Dan Carpenter <dan.carpenter@oracle.com>; Pavel Shilovskiy <pshilov@microsoft.com>; Steven French <Steven.French@microsoft.com>; Aurelien Aptel <aaptel@suse.com>; Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.2 02/45] smb3: fix unmount hang in open_shroot

From: Steve French <stfrench@microsoft.com>

[ Upstream commit 96d9f7ed00b86104bf03adeffc8980897e9694ab ]

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")

This is version 2 of this patch. An earlier version of this patch "smb3: fix unmount hang in open_shroot" had a problem found by Dan.

Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/smb2ops.c | 21 +++++++++++----------
1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c index 42de31d206169..8ae8ef526b4a5 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -656,6 +656,15 @@ 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;

@@ -677,7 +686,7 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)

rc = SMB2_open_init(tcon, &rqst[0], &oplock, &oparms, &utf16_path);
if (rc)
- goto oshr_exit;
+ goto oshr_free;
smb2_set_next_command(tcon, &rqst[0]);

memset(&qi_iov, 0, sizeof(qi_iov));
@@ -690,18 +699,10 @@ int open_shroot(unsigned int xid, struct cifs_tcon *tcon, struct cifs_fid *pfid)
sizeof(struct smb2_file_all_info) +
PATH_MAX * 2, 0, NULL);
if (rc)
- goto oshr_exit;
+ goto oshr_free;

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


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