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-rw-r--r--sys/geom/geom_vol_ffs.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/sys/geom/geom_vol_ffs.c b/sys/geom/geom_vol_ffs.c
index 94175f74e236..d90222f7f6e7 100644
--- a/sys/geom/geom_vol_ffs.c
+++ b/sys/geom/geom_vol_ffs.c
@@ -88,6 +88,16 @@ g_vol_ffs_taste(struct g_class *mp, struct g_provider *pp, int flags)
* provider based on that.
*/
for (sb=0; (superblock = superblocks[sb]) != -1; sb++) {
+ /*
+ * Take care not to issue an invalid I/O request. The
+ * offset and size of the superblock candidate must be
+ * multiples of the provider's sector size, otherwise an
+ * FFS can't exist on the provider anyway.
+ */
+ if (superblock % cp->provider->sectorsize != 0 ||
+ SBLOCKSIZE % cp->provider->sectorsize != 0)
+ continue;
+
fs = (struct fs *) g_read_data(cp, superblock,
SBLOCKSIZE, &error);
if (fs == NULL || error != 0)