[Xen-devel] [PATCH] PV-GRUB: fix blk access at end of disk

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

GRUB usually always loads a whole disk track, even if that means going
beyond the end of the disk.  We thus have to gracefully return an error,
instead of letting the blkfront go panic.

Signed-off-by: Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>

diff --git a/stubdom/grub/mini-os.c b/stubdom/grub/mini-os.c
index 8cecf90..64ab962 100644
--- a/stubdom/grub/mini-os.c
+++ b/stubdom/grub/mini-os.c
@@ -126,6 +126,9 @@ biosdisk (int read, int drive, struct geometry *geometry,
     if (i >= blk_nb)
         return -1;
 
+    if (sector + nsec > geometry->total_sectors)
+      return -1;
+
     aiocb.aio_dev = blk_dev[i];
     aiocb.aio_buf = addr;
     aiocb.aio_nbytes = (size_t)nsec * blk_info[i].sector_size;

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