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authorJulia Lawall <julia@diku.dk>2009-12-23 07:52:31 -0500
committerTheodore Ts'o <tytso@mit.edu>2009-12-23 07:52:31 -0500
commitd3533d72e7478a61a3e1936956fc825289a2acf4 (patch)
tree5932e890fa8185bd792a94730725665a26a6102a /fs
parenta6b43e382568a49cc64291bfaddf896652d44f70 (diff)
ext4: Eliminate potential double free on error path
b_entry_name and buffer are initially NULL, are initialized within a loop to the result of calling kmalloc, and are freed at the bottom of this loop. The loop contains gotos to cleanup, which also frees b_entry_name and buffer. Some of these gotos are before the reinitializations of b_entry_name and buffer. To maintain the invariant that b_entry_name and buffer are NULL at the top of the loop, and thus acceptable arguments to kfree, these variables are now set to NULL after the kfrees. This seems to be the simplest solution. A more complicated solution would be to introduce more labels in the error handling code at the end of the function. A simplified version of the semantic match that finds this problem is as follows: (http://coccinelle.lip6.fr/) // <smpl> @r@ identifier E; expression E1; iterator I; statement S; @@ *kfree(E); ... when != E = E1 when != I(E,...) S when != &E *kfree(E); // </smpl> Signed-off-by: Julia Lawall <julia@diku.dk> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Diffstat (limited to 'fs')
-rw-r--r--fs/ext4/xattr.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index 83218bebbc7c..f3a2f7ed45aa 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -1332,6 +1332,8 @@ retry:
1332 goto cleanup; 1332 goto cleanup;
1333 kfree(b_entry_name); 1333 kfree(b_entry_name);
1334 kfree(buffer); 1334 kfree(buffer);
1335 b_entry_name = NULL;
1336 buffer = NULL;
1335 brelse(is->iloc.bh); 1337 brelse(is->iloc.bh);
1336 kfree(is); 1338 kfree(is);
1337 kfree(bs); 1339 kfree(bs);