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xfs: use MMAPLOCK around filemap_map_pages()

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The page faultround path ->map_pages is implemented in XFS via
filemap_map_pages(). This function checks that pages found in page
cache lookups have not raced with truncate based invalidation by
checking page->mapping is correct and page->index is within EOF.

However, we've known for a long time that this is not sufficient to
protect against races with invalidations done by operations that do
not change EOF. e.g. hole punching and other fallocate() based
direct extent manipulations. The way we protect against these
races is we wrap the page fault operations in a XFS_MMAPLOCK_SHARED
lock so they serialise against fallocate and truncate before calling
into the filemap function that processes the fault.

Do the same for XFS's ->map_pages implementation to close this
potential data corruption issue.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Dave Chinner 2020-06-30 11:28:53 -07:00 committed by Darrick J. Wong
parent e2aaee9cd3
commit cd647d5651
1 changed files with 14 additions and 1 deletions
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15
fs/xfs/xfs_file.c
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@ -1263,10 +1263,23 @@ xfs_filemap_pfn_mkwrite(
return __xfs_filemap_fault(vmf, PE_SIZE_PTE, true);
}
static void
xfs_filemap_map_pages(
struct vm_fault *vmf,
pgoff_t start_pgoff,
pgoff_t end_pgoff)
{
struct inode *inode = file_inode(vmf->vma->vm_file);
xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
filemap_map_pages(vmf, start_pgoff, end_pgoff);
xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
}
static const struct vm_operations_struct xfs_file_vm_ops = {
.fault = xfs_filemap_fault,
.huge_fault = xfs_filemap_huge_fault,
.map_pages = filemap_map_pages,
.map_pages = xfs_filemap_map_pages,
.page_mkwrite = xfs_filemap_page_mkwrite,
.pfn_mkwrite = xfs_filemap_pfn_mkwrite,
};