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| author | Al Viro <viro@zeniv.linux.org.uk> | 2019-11-03 21:45:04 +0300 |
|---|---|---|
| committer | Al Viro <viro@zeniv.linux.org.uk> | 2019-11-10 19:57:44 +0300 |
| commit | e72b9dd6a5f17d0fb51f16f8685f3004361e83d0 (patch) | |
| tree | 19a562a037fad18df276c5847f43b57b646da2dc /fs/ecryptfs/inode.c | |
| parent | bcf0d9d4b76976f892154efdfc509b256fd898e8 (diff) | |
| download | linux-e72b9dd6a5f17d0fb51f16f8685f3004361e83d0.tar.xz | |
ecryptfs_lookup_interpose(): lower_dentry->d_inode is not stable
lower_dentry can't go from positive to negative (we have it pinned),
but it *can* go from negative to positive. So fetching ->d_inode
into a local variable, doing a blocking allocation, checking that
now ->d_inode is non-NULL and feeding the value we'd fetched
earlier to a function that won't accept NULL is not a good idea.
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/ecryptfs/inode.c')
| -rw-r--r-- | fs/ecryptfs/inode.c | 12 |
1 files changed, 10 insertions, 2 deletions
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c index a905d5f4f3b0..3c2298721359 100644 --- a/fs/ecryptfs/inode.c +++ b/fs/ecryptfs/inode.c @@ -319,7 +319,7 @@ 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 inode *inode, *lower_inode = d_inode(lower_dentry); + struct inode *inode, *lower_inode; struct ecryptfs_dentry_info *dentry_info; struct vfsmount *lower_mnt; int rc = 0; @@ -339,7 +339,15 @@ static struct dentry *ecryptfs_lookup_interpose(struct dentry *dentry, dentry_info->lower_path.mnt = lower_mnt; dentry_info->lower_path.dentry = lower_dentry; - if (d_really_is_negative(lower_dentry)) { + /* + * negative dentry can go positive under us here - its parent is not + * locked. That's OK and that could happen just as we return from + * ecryptfs_lookup() anyway. Just need to be careful and fetch + * ->d_inode only once - it's not stable here. + */ + lower_inode = READ_ONCE(lower_dentry->d_inode); + + if (!lower_inode) { /* We want to add because we couldn't find in lower */ d_add(dentry, NULL); return NULL; |