As requested I changed the buffer size malloced to be more obvious -
in this case to match exactly what is returned from the first call (ie
snapshot length + the sizeof the snapshot info structure which
precedes the snapshot list, ie 16 bytes). The snapshot array size is
12 bytes, but rounding it to 8 byte boundary causes the minimum to be
16 bytes.
On Thu, Mar 28, 2019 at 11:02 AM David Disseldorp <ddiss@xxxxxxx> wrote:
>
> On Thu, 28 Mar 2019 05:05:35 -0500, Steve French wrote:
>
> > + /* Now that we know the size, query the list from the server */
> > +
> > + /* Make sure the buf size is big enough even to handle unexpected server behavior */
> > + buf = malloc(snap_inf.snapshot_array_size + 300);
>
> The buffer length calculations seem pretty arbitrary here, wouldn't it
> make sense to use something like the following (with a maximum limit)?
> sizeof(struct smb_snapshot_array) +
> (snap_inf.number_of_snapshots * GMT_TOKEN_LEN)
>
> Cheers, David
--
Thanks,
Steve
From da08b29a8278f49edffdd4ebe2132b74786dda6d Mon Sep 17 00:00:00 2001
From: Steve French <stfrench@xxxxxxxxxxxxx>
Date: Fri, 29 Mar 2019 03:05:55 -0500
Subject: [PATCH] smbinfo: Add ability to query snapshots (previous versions)
Allow listing SMB3 snapshots (previous versions of shares)
Signed-off-by: Steve French <stfrench@xxxxxxxxxxxxx>
Reviewed-by: Ronnie Sahlberg <lsahlber@xxxxxxxxxx>
---
smbinfo.c | 87 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 87 insertions(+)
diff --git a/smbinfo.c b/smbinfo.c
index 33fca95..7cffb84 100644
--- a/smbinfo.c
+++ b/smbinfo.c
@@ -89,6 +89,8 @@ usage(char *name)
" Prints the security descriptor for a cifs file.\n"
" quota:\n"
" Prints the quota for a cifs file.\n"
+ " list-snapshots:\n"
+ " List the previous versions of the volume that backs this file.\n"
" fsctl-getobjid:\n"
" Prints the objectid of the file and GUID of the underlying volume.\n",
name);
@@ -966,6 +968,89 @@ quota(int f)
free(qi);
}
+
+struct smb_snapshot_array {
+ int32_t number_of_snapshots;
+ int32_t number_of_snapshots_returned;
+ int32_t snapshot_array_size;
+ char snapshot_data[0];
+};
+
+
+static void print_snapshots(struct smb_snapshot_array *psnap)
+{
+ int current_snapshot_entry = 0;
+
+ printf("Number of snapshots: %d Number of snapshots returned: %d\n",
+ psnap->number_of_snapshots,
+ psnap->number_of_snapshots_returned);
+ printf("Snapshot list:");
+
+ for (int i = 0; i < psnap->snapshot_array_size; i++) {
+ if (psnap->snapshot_data[i] == '@') {
+ current_snapshot_entry++;
+ printf("\n%d) ", current_snapshot_entry);
+ }
+ printf("%c", psnap->snapshot_data[i]);
+ }
+ printf("\n");
+}
+
+#define CIFS_ENUMERATE_SNAPSHOTS _IOR(CIFS_IOCTL_MAGIC, 6, struct smb_snapshot_array)
+
+#define MIN_SNAPSHOT_ARRAY_SIZE 16 /* See MS-SMB2 section 3.3.5.15.1 */
+
+static void
+list_snapshots(int f)
+{
+
+ struct smb_snapshot_array snap_inf;
+ struct smb_snapshot_array *buf;
+
+ /*
+ * When first field in structure we pass in here is zero, cifs.ko can
+ * recognize that this is the first query and that it must set the SMB3
+ * FSCTL response buffer size (in the request) to exactly 16 bytes
+ * (which is required by some servers to process the initial query)
+ */
+ snap_inf.number_of_snapshots = 0;
+ snap_inf.number_of_snapshots_returned = 0;
+ snap_inf.snapshot_array_size = sizeof(struct smb_snapshot_array);
+
+ /* Query the number of snapshots so we know how much to allocate */
+ if (ioctl(f, CIFS_ENUMERATE_SNAPSHOTS, &snap_inf) < 0) {
+ fprintf(stderr, "Querying snapshots failed with %s\n", strerror(errno));
+ exit(1);
+ }
+
+ if (snap_inf.number_of_snapshots == 0)
+ return;
+
+ /* Now that we know the size, query the list from the server */
+
+ buf = malloc(snap_inf.snapshot_array_size + MIN_SNAPSHOT_ARRAY_SIZE);
+
+ if (buf == NULL) {
+ printf("Failed, out of memory.\n");
+ exit(1);
+ }
+ /*
+ * first parm is non-zero which allows cifs.ko to recognize that this is
+ * the second query (it has to set response buf size larger)
+ */
+ buf->number_of_snapshots = snap_inf.number_of_snapshots;
+
+ buf->snapshot_array_size = snap_inf.snapshot_array_size;
+
+ if (ioctl(f, CIFS_ENUMERATE_SNAPSHOTS, buf) < 0) {
+ fprintf(stderr, "Querying snapshots failed with %s\n", strerror(errno));
+ exit(1);
+ }
+
+ print_snapshots(buf);
+ free(buf);
+}
+
int main(int argc, char *argv[])
{
int c;
@@ -1016,6 +1101,8 @@ int main(int argc, char *argv[])
secdesc(f);
else if (!strcmp(argv[optind], "quota"))
quota(f);
+ else if (!strcmp(argv[optind], "list-snapshots"))
+ list_snapshots(f);
else if (!strcmp(argv[1], "fsctl-getobjid"))
fsctlgetobjid(f);
else {
--
2.17.1
