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xfs: assure zeroed memory buffers for certain kmem allocations

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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>
This commit is contained in:
Bill O'Donnell
2019-10-04 16:38:44 -07:00
committed by Darrick J. Wong
parent d5cc14d9f9
commit 3219e8cf0d
3 changed files with 13 additions and 3 deletions
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12
fs/xfs/xfs_buf.c
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@@ -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;