From 1a6948737323436ff5925f2e092fcbbce429deb3 Mon Sep 17 00:00:00 2001 From: Jamie Liu Date: Tue, 13 Oct 2020 12:43:03 -0700 Subject: Don't read beyond EOF when inserting into sentry page cache. The sentry page cache stores file contents at page granularity; this is necessary for memory mappings. Thus file offset ranges passed to fsutil.FileRangeSet.Fill() must be page-aligned. If the read callback passed to Fill() returns (partial read, nil error) when reading up to EOF (which is the case for p9.ClientFile.ReadAt() since 9P's Rread cannot convey both a partial read and EOF), Fill() will re-invoke the read callback to try to read from EOF to the end of the containing page, which is harmless but needlessly expensive. Fix this by handling file size explicitly in fsutil.FileRangeSet.Fill(). PiperOrigin-RevId: 336934075 --- pkg/sentry/fs/tmpfs/inode_file.go | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'pkg/sentry/fs/tmpfs') diff --git a/pkg/sentry/fs/tmpfs/inode_file.go b/pkg/sentry/fs/tmpfs/inode_file.go index 1dc75291d..fc0498f17 100644 --- a/pkg/sentry/fs/tmpfs/inode_file.go +++ b/pkg/sentry/fs/tmpfs/inode_file.go @@ -613,7 +613,7 @@ func (f *fileInodeOperations) Translate(ctx context.Context, required, optional } mf := f.kernel.MemoryFile() - cerr := f.data.Fill(ctx, required, optional, mf, f.memUsage, func(_ context.Context, dsts safemem.BlockSeq, _ uint64) (uint64, error) { + cerr := f.data.Fill(ctx, required, optional, uint64(f.attr.Size), mf, f.memUsage, func(_ context.Context, dsts safemem.BlockSeq, _ uint64) (uint64, error) { // Newly-allocated pages are zeroed, so we don't need to do anything. return dsts.NumBytes(), nil }) -- cgit v1.2.3