diff options
| author | Al Viro <viro@zeniv.linux.org.uk> | 2019-11-03 13:55:43 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-11-20 18:45:18 +0100 |
| commit | bdae2f7b2031cbeebca93267bef5e829e55c03ca (patch) | |
| tree | 08af88c7a8b41f0032139d47dd349b8320662748 /fs/ecryptfs | |
| parent | beb3860c2e0edb81786fbeaeace366174b59d5ef (diff) | |
ecryptfs_lookup_interpose(): lower_dentry->d_parent is not stable either
commit 762c69685ff7ad5ad7fee0656671e20a0c9c864d upstream.
We need to get the underlying dentry of parent; sure, absent the races
it is the parent of underlying dentry, but there's nothing to prevent
losing a timeslice to preemtion in the middle of evaluation of
lower_dentry->d_parent->d_inode, having another process move lower_dentry
around and have its (ex)parent not pinned anymore and freed on memory
pressure. Then we regain CPU and try to fetch ->d_inode from memory
that is freed by that point.
dentry->d_parent *is* stable here - it's an argument of ->lookup() and
we are guaranteed that it won't be moved anywhere until we feed it
to d_add/d_splice_alias. So we safely go that way to get to its
underlying dentry.
Cc: stable@vger.kernel.org # since 2009 or so
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'fs/ecryptfs')
| -rw-r--r-- | fs/ecryptfs/inode.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index 60a095b09b24..6578a1cb4d39 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -325,9 +325,9 @@ static int ecryptfs_i_size_read(struct dentry *dentry, struct inode *inode) static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry, struct dentry *lower_dentry) { + struct path *path = ecryptfs_dentry_to_lower_path(dentry->d_parent); struct inode *inode, *lower_inode; struct ecryptfs_dentry_info *dentry_info; - struct vfsmount *lower_mnt; int rc = 0; dentry_info = kmem_cache_alloc(ecryptfs_dentry_info_cache, GFP_KERNEL); @@ -336,13 +336,12 @@ static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry, return ERR_PTR(-ENOMEM); } - lower_mnt = mntget(ecryptfs_dentry_to_lower_mnt(dentry->d_parent)); fsstack_copy_attr_atime(d_inode(dentry->d_parent), - d_inode(lower_dentry->d_parent)); + d_inode(path->dentry)); BUG_ON(!d_count(lower_dentry)); ecryptfs_set_dentry_private(dentry, dentry_info); - dentry_info->lower_path.mnt = lower_mnt; + dentry_info->lower_path.mnt = mntget(path->mnt); dentry_info->lower_path.dentry = lower_dentry; /* |