[SMB3] Fix snapshot enumeration to Azure
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Message ID CAH2r5muXau+BH4gj4gFsYnKj1k-OK+KJZp_FT_Et5wT3jK65Sg@mail.gmail.com
State New
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Series
  • [SMB3] Fix snapshot enumeration to Azure
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Commit Message

Steve French March 28, 2019, 8:45 a.m. UTC
Some servers (see MS-SMB2 protocol specification note 310 and
section 3.3.5.15.1) expect that the FSCTL enumerate snapshots
is done twice, with the first query having EXACTLY the minimum
size response buffer requested (16 bytes) which refreshes
the snapshot list (otherwise that and subsequent queries get
an empty list returned).  So had to add code to set
the maximum response size differently for the first snapshot
query (which gets the size needed for the second query which
contains the actual list of snapshots).

This better matches what Windows client does as well.

Patch
diff mbox series

From f11f658baccb6c59786ae5a3cb65145ed655cf2f Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@microsoft.com>
Date: Thu, 28 Mar 2019 03:37:52 -0500
Subject: [PATCH] smb3: Fix enumerating snapshots to Azure

Some servers (see MS-SMB2 protocol specification note 310 and
section 3.3.5.15.1) expect that the FSCTL enumerate snapshots
is done twice, with the first query having EXACTLY the minimum
size response buffer requested (16 bytes) which refreshes
the snapshot list (otherwise that and subsequent queries get
an empty list returned).  So had to add code to set
the maximum response size differently for the first snapshot
query (which gets the size needed for the second query which
contains the actual list of snapshots).

Signed-off-by: Steve French <stfrench@microsoft.com>
---
 fs/cifs/smb2ops.c   |  7 +++++--
 fs/cifs/smb2pdu.c   | 31 +++++++++++++++++++++++++++----
 fs/cifs/smb2proto.h |  3 ++-
 3 files changed, 34 insertions(+), 7 deletions(-)

diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 7cfafac255aa..e755236af8ff 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -1402,7 +1402,7 @@  smb2_ioctl_query_info(const unsigned int xid,
 			rc = SMB2_ioctl_init(tcon, &rqst[1],
 					     COMPOUND_FID, COMPOUND_FID,
 					     qi.info_type, true, NULL,
-					     0);
+					     0, false);
 		}
 	} else if (qi.flags == PASSTHRU_QUERY_INFO) {
 		memset(&qi_iov, 0, sizeof(qi_iov));
@@ -1820,6 +1820,9 @@  smb3_enum_snapshots(const unsigned int xid, struct cifs_tcon *tcon,
 	int rc;
 	struct smb_snapshot_array snapshot_in;
 
+	if (get_user(ret_data_len, (unsigned int __user *)ioc_buf))
+		return -EFAULT;
+
 	rc = SMB2_ioctl(xid, tcon, cfile->fid.persistent_fid,
 			cfile->fid.volatile_fid,
 			FSCTL_SRV_ENUMERATE_SNAPSHOTS,
@@ -2656,7 +2659,7 @@  static long smb3_zero_range(struct file *file, struct cifs_tcon *tcon,
 	rc = SMB2_ioctl_init(tcon, &rqst[num++], cfile->fid.persistent_fid,
 			     cfile->fid.volatile_fid, FSCTL_SET_ZERO_DATA,
 			     true /* is_fctl */, (char *)&fsctl_buf,
-			     sizeof(struct file_zero_data_information));
+			     sizeof(struct file_zero_data_information), false);
 	if (rc)
 		goto zero_range_exit;
 
diff --git a/fs/cifs/smb2pdu.c b/fs/cifs/smb2pdu.c
index 21ac19ff19cb..bc830519d7eb 100644
--- a/fs/cifs/smb2pdu.c
+++ b/fs/cifs/smb2pdu.c
@@ -2478,7 +2478,8 @@  SMB2_open(const unsigned int xid, struct cifs_open_parms *oparms, __le16 *path,
 int
 SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 		u64 persistent_fid, u64 volatile_fid, u32 opcode,
-		bool is_fsctl, char *in_data, u32 indatalen)
+		bool is_fsctl, char *in_data, u32 indatalen,
+		bool rsp_buf_not_allowed)
 {
 	struct smb2_ioctl_req *req;
 	struct kvec *iov = rqst->rq_iov;
@@ -2529,7 +2530,18 @@  SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 	 * in responses (except for read responses which can be bigger.
 	 * We may want to bump this limit up
 	 */
-	req->MaxOutputResponse = cpu_to_le32(CIFSMaxBufSize);
+
+	/*
+	 * Servers like Azure expect first query to be minimal (to get number of
+	 * previous versions) so the response size must be specified as EXACTLY
+	 * sizeof(struct snapshot_array) which is 16 when rounded up to multiple
+	 * of eight bytes.
+	 */
+
+	if (rsp_buf_not_allowed)
+		req->MaxOutputResponse = cpu_to_le32(16);
+	else
+		req->MaxOutputResponse = cpu_to_le32(CIFSMaxBufSize);
 
 	if (is_fsctl)
 		req->Flags = cpu_to_le32(SMB2_0_IOCTL_IS_FSCTL);
@@ -2567,12 +2579,23 @@  SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 	int resp_buftype = CIFS_NO_BUFFER;
 	int rc = 0;
 	int flags = 0;
+	bool rsp_buf_not_allowed = false;
 
 	cifs_dbg(FYI, "SMB2 IOCTL\n");
 
 	if (out_data != NULL)
 		*out_data = NULL;
 
+
+	/*
+	 * Servers like Azure expect first query to be minimal (to get number of
+	 * previous versions) so the response size must be specified as EXACTLY
+	 * sizeof(struct snapshot_array) which is 16 when rounded up to multiple
+	 * of eight bytes.
+	 */
+	if ((opcode == FSCTL_SRV_ENUMERATE_SNAPSHOTS) && plen && (*plen == 0))
+		rsp_buf_not_allowed = true;
+
 	/* zero out returned data len, in case of error */
 	if (plen)
 		*plen = 0;
@@ -2593,8 +2616,8 @@  SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon, u64 persistent_fid,
 	rqst.rq_iov = iov;
 	rqst.rq_nvec = SMB2_IOCTL_IOV_SIZE;
 
-	rc = SMB2_ioctl_init(tcon, &rqst, persistent_fid, volatile_fid,
-			     opcode, is_fsctl, in_data, indatalen);
+	rc = SMB2_ioctl_init(tcon, &rqst, persistent_fid, volatile_fid, opcode,
+			     is_fsctl, in_data, indatalen, rsp_buf_not_allowed);
 	if (rc)
 		goto ioctl_exit;
 
diff --git a/fs/cifs/smb2proto.h b/fs/cifs/smb2proto.h
index 3c32d0cfea69..6f2fc1685199 100644
--- a/fs/cifs/smb2proto.h
+++ b/fs/cifs/smb2proto.h
@@ -146,7 +146,8 @@  extern int SMB2_ioctl(const unsigned int xid, struct cifs_tcon *tcon,
 		     char **out_data, u32 *plen /* returned data len */);
 extern int SMB2_ioctl_init(struct cifs_tcon *tcon, struct smb_rqst *rqst,
 			   u64 persistent_fid, u64 volatile_fid, u32 opcode,
-			   bool is_fsctl, char *in_data, u32 indatalen);
+			   bool is_fsctl, char *in_data, u32 indatalen,
+			   bool rsp_buf_not_allowed);
 extern void SMB2_ioctl_free(struct smb_rqst *rqst);
 extern int SMB2_close(const unsigned int xid, struct cifs_tcon *tcon,
 		      u64 persistent_file_id, u64 volatile_file_id);
-- 
2.17.1