nfsd: better layoutupdate bounds-checking

You could add any multiple of 2^32/PNFS_SCSI_RANGE_SIZE to nr_iomaps and
still pass this check.  You'd probably still fail the following kcalloc,
but best to be paranoid since this is from-the-wire data.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/fs/nfsd/blocklayoutxdr.c b/fs/nfsd/blocklayoutxdr.c
index ca1883668810..6c3b316f932e 100644
--- a/fs/nfsd/blocklayoutxdr.c
+++ b/fs/nfsd/blocklayoutxdr.c
@@ -105,18 +105,22 @@ nfsd4_block_decode_layoutupdate(__be32 *p, u32 len, struct iomap **iomapp,
                 u32 block_size)
 {
         struct iomap *iomaps;
-        u32 nr_iomaps, expected, i;
+        u32 nr_iomaps, i;
 
         if (len < sizeof(u32)) {
                 dprintk("%s: extent array too small: %u\n", __func__, len);
                 return -EINVAL;
         }
+        len -= sizeof(u32);
+        if (len % PNFS_BLOCK_EXTENT_SIZE) {
+                dprintk("%s: extent array invalid: %u\n", __func__, len);
+                return -EINVAL;
+        }
 
         nr_iomaps = be32_to_cpup(p++);
-        expected = sizeof(__be32) + nr_iomaps * PNFS_BLOCK_EXTENT_SIZE;
-        if (len != expected) {
+        if (nr_iomaps != len / PNFS_BLOCK_EXTENT_SIZE) {
                 dprintk("%s: extent array size mismatch: %u/%u\n",
-                        __func__, len, expected);
+                        __func__, len, nr_iomaps);
                 return -EINVAL;
         }