xfs: zero inode fork buffer at allocation

When we first allocate or resize an inline inode fork, we round up
the allocation to 4 byte alingment to make journal alignment
constraints. We don't clear the unused bytes, so we can copy up to
three uninitialised bytes into the journal. Zero those bytes so we
only ever copy zeros into the journal.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Allison Henderson <allison.henderson@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

diff --git a/fs/xfs/libxfs/xfs_inode_fork.c b/fs/xfs/libxfs/xfs_inode_fork.c
index 9aee4a1e2fe98219596ee2622b3ffaeb860677e3..a15ff38c3d41e2cc563f13053b7aa1c2caa2731e 100644 (file)
--- a/fs/xfs/libxfs/xfs_inode_fork.c
+++ b/fs/xfs/libxfs/xfs_inode_fork.c
@@ -50,8 +50,13 @@ xfs_init_local_fork(
                mem_size++;
 
        if (size) {
+               /*
+                * As we round up the allocation here, we need to ensure the
+                * bytes we don't copy data into are zeroed because the log
+                * vectors still copy them into the journal.
+                */
                real_size = roundup(mem_size, 4);
-               ifp->if_u1.if_data = kmem_alloc(real_size, KM_NOFS);
+               ifp->if_u1.if_data = kmem_zalloc(real_size, KM_NOFS);
                memcpy(ifp->if_u1.if_data, data, size);
                if (zero_terminate)
                        ifp->if_u1.if_data[size] = '\0';
@@ -500,10 +505,11 @@ xfs_idata_realloc(
        /*
         * For inline data, the underlying buffer must be a multiple of 4 bytes
         * in size so that it can be logged and stay on word boundaries.
-        * We enforce that here.
+        * We enforce that here, and use __GFP_ZERO to ensure that size
+        * extensions always zero the unused roundup area.
         */
        ifp->if_u1.if_data = krealloc(ifp->if_u1.if_data, roundup(new_size, 4),
-                                     GFP_NOFS | __GFP_NOFAIL);
+                                     GFP_NOFS | __GFP_NOFAIL | __GFP_ZERO);
        ifp->if_bytes = new_size;
 }