xfs: zero inode fork buffer at allocation

Source kernel commit: cb512c921639613ce03f87e62c5e93ed9fe8c84d

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>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>

diff --git a/libxfs/xfs_inode_fork.c b/libxfs/xfs_inode_fork.c
index da592329188ef710ac4baeffc6998116f334d1ea..ac3692b5fcdb7a7aafca7bb766c5684389cc8df5 100644 (file)
--- a/libxfs/xfs_inode_fork.c
+++ b/libxfs/xfs_inode_fork.c
@@ -48,8 +48,13 @@ 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';
@@ -498,10 +503,11 @@ 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;
 }