linux-kernel - [PATCH][next][V3] btrfs: fix memory leak of path on error return path

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Message-Id: <20190705072624.14163-1-colin.king@canonical.com>
Date:   Fri,  5 Jul 2019 08:26:24 +0100
From:   Colin King <colin.king@...onical.com>
To:     Chris Mason <clm@...com>, Josef Bacik <josef@...icpanda.com>,
        David Sterba <dsterba@...e.com>, linux-btrfs@...r.kernel.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next][V3] btrfs: fix memory leak of path on error return path

From: Colin Ian King <colin.king@...onical.com>

Currently if the allocation of roots or tmp_ulist fails the error handling
does not free up the allocation of path causing a memory leak. Fix this and
other similar leaks by moving the call of btrfs_free_path from label out
to label out_free_ulist.

Kudos to David Sterba for spotting the issue in my original fix and suggesting
the correct way to fix the leak and Anand Jain for spotting a double free
issue.

Addresses-Coverity: ("Resource leak")
Fixes: 5911c8fe05c5 ("btrfs: fiemap: preallocate ulists for btrfs_check_shared")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
V2: move the btrfs_free_path to the out_free_ulist label as suggested by
     David Sterba as the correct fix.
V3: fix double free as identified Anand Jain
---

 fs/btrfs/extent_io.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 1eb671c16ff1..9de119194f8e 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4613,7 +4613,6 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 	ret = btrfs_lookup_file_extent(NULL, root, path,
 			btrfs_ino(BTRFS_I(inode)), -1, 0);
 	if (ret < 0) {
-		btrfs_free_path(path);
 		goto out_free_ulist;
 	} else {
 		WARN_ON(!ret);
@@ -4766,11 +4765,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		ret = emit_last_fiemap_cache(fieinfo, &cache);
 	free_extent_map(em);
 out:
-	btrfs_free_path(path);
 	unlock_extent_cached(&BTRFS_I(inode)->io_tree, start, start + len - 1,
 			     &cached_state);
 
 out_free_ulist:
+	btrfs_free_path(path);
 	ulist_free(roots);
 	ulist_free(tmp_ulist);
 	return ret;
-- 
2.20.1