[PATCH v3 1/3] ovl: check type and offset of struct vfsmount in ovl_entry

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Porting overlayfs to the new amount api I started experiencing random
crashes that couldn't be explained easily. So after much debugging and
reasoning it became clear that struct ovl_entry requires the point to
struct vfsmount to be the first member and of type struct vfsmount.

During the port I added a new member at the beginning of struct
ovl_entry which broke all over the place in the form of random crashes
and cache corruptions. While there's a comment in ovl_free_fs() to the
effect of "Hack! Reuse ofs->layers as a vfsmount array before freeing
it" there's no such comment on struct ovl_entry which makes this easy to
trip over.

Add a comment and two static asserts for both the offset and the type of
pointer in struct ovl_entry.

Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
---
 fs/overlayfs/ovl_entry.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index c6c7d09b494e..e5207c4bf5b8 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -32,6 +32,7 @@ struct ovl_sb {
 };
 
 struct ovl_layer {
+	/* ovl_free_fs() relies on @mnt being the first member! */
 	struct vfsmount *mnt;
 	/* Trap in ovl inode cache */
 	struct inode *trap;
@@ -42,6 +43,14 @@ struct ovl_layer {
 	int fsid;
 };
 
+/*
+ * ovl_free_fs() relies on @mnt being the first member when unmounting
+ * the private mounts created for each layer. Let's check both the
+ * offset and type.
+ */
+static_assert(offsetof(struct ovl_layer, mnt) == 0);
+static_assert(__same_type(typeof_member(struct ovl_layer, mnt), struct vfsmount *));
+
 struct ovl_path {
 	const struct ovl_layer *layer;
 	struct dentry *dentry;

-- 
2.34.1




[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux