xfs: assure zeroed memory buffers for certain kmem allocations

Guarantee zeroed memory buffers for cases where potential memory
leak to disk can occur. In these cases, kmem_alloc is used and
doesn't zero the buffer, opening the possibility of information
leakage to disk.

Use existing infrastucture (xfs_buf_allocate_memory) to obtain
the already zeroed buffer from kernel memory.

This solution avoids the performance issue that would occur if a
wholesale change to replace kmem_alloc with kmem_zalloc was done.

Signed-off-by: Bill O'Donnell <billodo@redhat.com>
[darrick: fix bitwise complaint about kmflag_mask]
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 21c243622a79d238dc13578dd0c22c1386d46ee9..0abba171aa89b6c948fc795201d2eee9734d6e06 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -345,6 +345,15 @@ xfs_buf_allocate_memory(
        unsigned short          page_count, i;
        xfs_off_t               start, end;
        int                     error;
+       xfs_km_flags_t          kmflag_mask = 0;
+
+       /*
+        * assure zeroed buffer for non-read cases.
+        */
+       if (!(flags & XBF_READ)) {
+               kmflag_mask |= KM_ZERO;
+               gfp_mask |= __GFP_ZERO;
+       }
 
        /*
         * for buffers that are contained within a single page, just allocate
@@ -354,7 +363,8 @@ xfs_buf_allocate_memory(
        size = BBTOB(bp->b_length);
        if (size < PAGE_SIZE) {
                int align_mask = xfs_buftarg_dma_alignment(bp->b_target);
-               bp->b_addr = kmem_alloc_io(size, align_mask, KM_NOFS);
+               bp->b_addr = kmem_alloc_io(size, align_mask,
+                                          KM_NOFS | kmflag_mask);
                if (!bp->b_addr) {
                        /* low memory - use alloc_page loop instead */
                        goto use_alloc_page;

diff --git a/fs/xfs/xfs_log.c b/fs/xfs/xfs_log.c
index a2beee9f74dabfad4eec3922a27cd8784135f2f5..641d07f30a2771731dede545dbeb219cef43f5a6 100644 (file)
--- a/fs/xfs/xfs_log.c
+++ b/fs/xfs/xfs_log.c
@@ -1443,7 +1443,7 @@ xlog_alloc_log(
                prev_iclog = iclog;
 
                iclog->ic_data = kmem_alloc_io(log->l_iclog_size, align_mask,
-                                               KM_MAYFAIL);
+                                               KM_MAYFAIL | KM_ZERO);
                if (!iclog->ic_data)
                        goto out_free_iclog;
 #ifdef DEBUG

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 508319039dceb54a3d1c167b82fa1c587fef709a..c1a514ffff55507e2986568868b7df915f3b00f8 100644 (file)
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -127,7 +127,7 @@ xlog_alloc_buffer(
        if (nbblks > 1 && log->l_sectBBsize > 1)
                nbblks += log->l_sectBBsize;
        nbblks = round_up(nbblks, log->l_sectBBsize);
-       return kmem_alloc_io(BBTOB(nbblks), align_mask, KM_MAYFAIL);
+       return kmem_alloc_io(BBTOB(nbblks), align_mask, KM_MAYFAIL | KM_ZERO);
 }
 
 /*