libblkid: avoid aligning out of probing area

When reading from the end of the device the IO size alignment could
enlarge the read buffer outside of the probing area.
This would then trigger a read failure.

Signed-off-by: Thomas Weißschuh <thomas@t-8ch.de>

diff --git a/libblkid/src/probe.c b/libblkid/src/probe.c
index 64e794467a4623b0e23f9563954764d9b67e641a..76905e1970fbbd4270190c2515611a6714fdc5fe 100644 (file)
--- a/libblkid/src/probe.c
+++ b/libblkid/src/probe.c
@@ -730,13 +730,18 @@ static int hide_buffer(blkid_probe pr, uint64_t off, uint64_t len)
 const unsigned char *blkid_probe_get_buffer(blkid_probe pr, uint64_t off, uint64_t len)
 {
        struct blkid_bufinfo *bf = NULL;
-       uint64_t real_off, bias;
+       uint64_t real_off, bias, len_align;
 
        bias = off % pr->io_size;
        off -= bias;
        len += bias;
-       if (len % pr->io_size)
-               len += pr->io_size - (len % pr->io_size);
+
+       if (len % pr->io_size) {
+               len_align = pr->io_size - (len % pr->io_size);
+
+               if (pr->off + off + len + len_align <= pr->size)
+                       len += len_align;
+       }
 
        real_off = pr->off + off;