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Commit c6081434 authored by Sudheer Shanka's avatar Sudheer Shanka
Browse files

Maintain the fuse buffer pool keyed by inode instead of threadId. 

In order to save memory, FuseAppLoop maintains a buffer pool to use
when dispatching the read/write requests. Currently, it uses
the threadId of the ProxyFileDescriptorCallback as the key for this
buffer pool and this can result in an issue when a caller creates
multiple ProxyFileDescriptors with ProxyFileDescriptorCallbacks
running on the same thread. When this happens, it is possible that
a buffer is reused before a read/write request which was using it
earlier has been handled and would result in data from read/write
requests on different fds getting mixed up.

Bug: 158568683
Test: atest --test-mapping apex/blobstore
Change-Id: Iaffd54f4430ecb3778f01c80f5a1684ac448f8dc
parent 38da493a

core/java/com/android/internal/os/FuseAppLoop.java

+9 −9
Original line number Diff line number Diff line
@@ -210,7 +210,7 @@ public class FuseAppLoop implements Handler.Callback { 
                        if (mInstance != 0) {

                            native_replySimple(mInstance, unique, FUSE_OK);

                        }

                        mBytesMap.stopUsing(entry.getThreadId());

                        mBytesMap.stopUsing(inode);

                        recycleLocked(args);

                    }

                    break;
@@ -270,7 +270,7 @@ public class FuseAppLoop implements Handler.Callback { 
                if (mInstance != 0) {

                    native_replyOpen(mInstance, unique, /* fh */ inode);

                    entry.opened = true;

                    return mBytesMap.startUsing(entry.getThreadId());

                    return mBytesMap.startUsing(inode);

                }

            } catch (ErrnoException error) {

                replySimpleLocked(unique, getError(error));
@@ -354,27 +354,27 @@ public class FuseAppLoop implements Handler.Callback { 
    }



    /**

     * Map between Thread ID and byte buffer.

     * Map between inode and byte buffer.

     */

    private static class BytesMap {

        final Map<Long, BytesMapEntry> mEntries = new HashMap<>();



        byte[] startUsing(long threadId) {

            BytesMapEntry entry = mEntries.get(threadId);

        byte[] startUsing(long inode) {

            BytesMapEntry entry = mEntries.get(inode);

            if (entry == null) {

                entry = new BytesMapEntry();

                mEntries.put(threadId, entry);

                mEntries.put(inode, entry);

            }

            entry.counter++;

            return entry.bytes;

        }



        void stopUsing(long threadId) {

            final BytesMapEntry entry = mEntries.get(threadId);

        void stopUsing(long inode) {

            final BytesMapEntry entry = mEntries.get(inode);

            Objects.requireNonNull(entry);

            entry.counter--;

            if (entry.counter <= 0) {

                mEntries.remove(threadId);

                mEntries.remove(inode);

            }

        }