[Qemu-block] [PATCH v2 1/1] block/sheepdog: fix argument passed to qemu_strtoul()

[Jeff Cody]

The function qemu_strtoul() reads 'unsigned long' sized data,
which is larger than uint32_t on 64-bit machines.

Even though the snap_id field in the header is 32-bits, we must
accomodate the full size in qemu_strtoul().

This patch also adds more meaningful error handling to the
qemu_strtoul() call, and subsequent results.

Reported-by: Paolo Bonzini <address@hidden>
Signed-off-by: Jeff Cody <address@hidden>
---
 block/sheepdog.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)

diff --git a/block/sheepdog.c b/block/sheepdog.c
index 8739acc..418f6ba 100644
--- a/block/sheepdog.c
+++ b/block/sheepdog.c
@@ -2543,7 +2543,7 @@ static int sd_snapshot_delete(BlockDriverState *bs,
                               const char *name,
                               Error **errp)
 {
-    uint32_t snap_id = 0;
+    unsigned long snap_id = 0;
     char snap_tag[SD_MAX_VDI_TAG_LEN];
     Error *local_err = NULL;
     int fd, ret;
@@ -2565,12 +2565,22 @@ static int sd_snapshot_delete(BlockDriverState *bs,
     memset(buf, 0, sizeof(buf));
     memset(snap_tag, 0, sizeof(snap_tag));
     pstrcpy(buf, SD_MAX_VDI_LEN, s->name);
-    if (qemu_strtoul(snapshot_id, NULL, 10, (unsigned long *)&snap_id)) {
-        return -1;
+    ret = qemu_strtoul(snapshot_id, NULL, 10, &snap_id);
+    if (ret) {
+        error_setg_errno(errp, -ret, "Invalid snapshot ID: %s",
+                         snapshot_id ? snapshot_id : "<null>");
+        return ret;
+    }
+
+    if (snap_id > UINT32_MAX) {
+        error_setg_errno(errp, EINVAL, "Snapshot ID numeric value %" PRId64
+                         " exceeds Sheepdog maximum of %" PRId32, snap_id,
+                          UINT32_MAX);
+        return -EINVAL;
     }
 
     if (snap_id) {
-        hdr.snapid = snap_id;
+        hdr.snapid = (uint32_t) snap_id;
     } else {
         pstrcpy(snap_tag, sizeof(snap_tag), snapshot_id);
         pstrcpy(buf + SD_MAX_VDI_LEN, SD_MAX_VDI_TAG_LEN, snap_tag);
-- 
1.9.3