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@xxxxxxxxxx>
---
v3: remove XBF_ZERO flag, and instead use XBF_READ flag only.
v2: zeroed buffer not required for XBF_READ case. Correct placement
and rename the XBF_ZERO flag.
fs/xfs/xfs_buf.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index 120ef99d09e8..6fbe63f34a68 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -345,6 +345,10 @@ xfs_buf_allocate_memory(
unsigned short page_count, i;
xfs_off_t start, end;
int error;
+ uint kmflag_mask = 0;
+
+ if (!(flags & XBF_READ))
+ kmflag_mask |= KM_ZERO;
/*
* for buffers that are contained within a single page, just allocate
@@ -354,7 +358,8 @@ 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;
@@ -391,7 +396,7 @@ xfs_buf_allocate_memory(
struct page *page;
uint retries = 0;
retry:
- page = alloc_page(gfp_mask);
+ page = alloc_page(gfp_mask | kmflag_mask);
if (unlikely(page == NULL)) {
if (flags & XBF_READ_AHEAD) {
bp->b_page_count = i;
--
2.21.0
