libext2fs: fix tdb.c mmap leak

When undoing an expansion of an mmap'd database while cancelling a
transaction, the tdb code prematurely decreases the variable that
tracks the file size, which leads to a region leak during the
subsequent unmap.  Fix this by maintaining a separate counter for the
region size.

(This is probably unnecessary since e2undo was the only user of tdb
transactions, but I suppose we could be proactive.)

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/ext2fs/tdb.c b/lib/ext2fs/tdb.c
index 61e30ed2fc5e99ab99feb35f361366ab2febb9e4..1d97685ece0caebc9ff060813c39d39af009ec92 100644 (file)
--- a/lib/ext2fs/tdb.c
+++ b/lib/ext2fs/tdb.c
@@ -246,6 +246,7 @@ struct tdb_context {
        int page_size;
        int max_dead_records;
        bool have_transaction_lock;
+       tdb_len_t real_map_size; /* how much space has been mapped */
 };
 
 
@@ -970,9 +971,10 @@ int tdb_munmap(struct tdb_context *tdb)
 
 #ifdef HAVE_MMAP
        if (tdb->map_ptr) {
-               int ret = munmap(tdb->map_ptr, tdb->map_size);
+               int ret = munmap(tdb->map_ptr, tdb->real_map_size);
                if (ret != 0)
                        return ret;
+               tdb->real_map_size = 0;
        }
 #endif
        tdb->map_ptr = NULL;
@@ -995,10 +997,12 @@ void tdb_mmap(struct tdb_context *tdb)
                 */
 
                if (tdb->map_ptr == MAP_FAILED) {
+                       tdb->real_map_size = 0;
                        tdb->map_ptr = NULL;
                        TDB_LOG((tdb, TDB_DEBUG_WARNING, "tdb_mmap failed for size %d (%s)\n",
                                 tdb->map_size, strerror(errno)));
                }
+               tdb->real_map_size = tdb->map_size;
        } else {
                tdb->map_ptr = NULL;
        }