[Xen-devel] [PATCH] linux-2.6.18/blkfront: avoid NULL de-reference in CDROM ioctl handling

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

Just like already done in the default case, for CDROM_GET_CAPABILITY
info->gd should not be blindly de-referenced, as the ioctl can be
called prior to full device setup having completed.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>

--- a/drivers/xen/blkfront/blkfront.c
+++ b/drivers/xen/blkfront/blkfront.c
@@ -566,12 +566,11 @@ int blkif_ioctl(struct block_device *bd,
                                return -EFAULT;
                return 0;
 
-       case CDROM_GET_CAPABILITY: {
-               struct gendisk *gd = info->gd;
-               if (gd->flags & GENHD_FL_CD)
+       case CDROM_GET_CAPABILITY:
+               if (info->gd && (info->gd->flags & GENHD_FL_CD))
                        return 0;
                return -EINVAL;
-       }
+
        default:
                if (info->mi && info->gd) {
                        switch (info->mi->major) {

Attachment: xen-cdrom-ioctl-check.patch
Description: Text document

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