linux-ext4 - [PATCH 37/31] libext2fs: fix tdb.c mmap leak

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Message-ID: <20141222185757.GL5368@birch.djwong.org>
Date:	Mon, 22 Dec 2014 10:57:57 -0800
From:	"Darrick J. Wong" <darrick.wong@...cle.com>
To:	tytso@....edu
Cc:	linux-ext4@...r.kernel.org
Subject: [PATCH 37/31] 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@...cle.com>
---
 lib/ext2fs/tdb.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/lib/ext2fs/tdb.c b/lib/ext2fs/tdb.c
index a916768..7317288 100644
--- 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;
 	}
--
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