[PATCH 17/17] ecryptfs: use vfs_get_link()
From: Miklos Szeredi <hidden>
Date: 2016-09-12 19:29:53
Also in:
lkml
Subsystem:
ecrypt file system, filesystems (vfs and infrastructure), the rest · Maintainers:
Tyler Hicks, Alexander Viro, Christian Brauner, Linus Torvalds
Here again we are copying form one buffer to another, while jumping through
hoops to make kernel memory look like userspace memory.
For no good reason, since vfs_get_link() provides exactly what is needed.
As a bonus, now the security hook for readlink is also called on the
underlying inode.
Note: this can be called from link-following context. But this is okay:
- not in RCU mode
- e54ad7f1ee26 ("proc: prevent stacking filesystems on top")
- ecryptfs is *reading* the underlying symlink not following it, so the
right security hook is being called
Signed-off-by: Miklos Szeredi <redacted>
Cc: Tyler Hicks <redacted>
---
fs/ecryptfs/inode.c | 27 ++++++++++++---------------
1 file changed, 12 insertions(+), 15 deletions(-)
diff --git a/fs/ecryptfs/inode.c b/fs/ecryptfs/inode.c
index fb2d831b7030..95e51b2af2de 100644
--- a/fs/ecryptfs/inode.c
+++ b/fs/ecryptfs/inode.c@@ -627,26 +627,23 @@ out_lock: static char *ecryptfs_readlink_lower(struct dentry *dentry, size_t *bufsiz) { + DEFINE_DELAYED_CALL(done); struct dentry *lower_dentry = ecryptfs_dentry_to_lower(dentry); - char *lower_buf; + const char *link; char *buf; - mm_segment_t old_fs; int rc; - lower_buf = kmalloc(PATH_MAX, GFP_KERNEL); - if (!lower_buf) - return ERR_PTR(-ENOMEM); - old_fs = get_fs(); - set_fs(get_ds()); - rc = vfs_readlink(lower_dentry, (char __user *)lower_buf, PATH_MAX); - set_fs(old_fs); - if (rc < 0) - goto out; + link = vfs_get_link(lower_dentry, d_inode(lower_dentry), &done); + if (IS_ERR(link)) + return ERR_CAST(link); + rc = ecryptfs_decode_and_decrypt_filename(&buf, bufsiz, dentry->d_sb, - lower_buf, rc); -out: - kfree(lower_buf); - return rc ? ERR_PTR(rc) : buf; + link, strlen(link)); + do_delayed_call(&done); + if (rc) + return ERR_PTR(rc); + + return buf; } static const char *ecryptfs_get_link(struct dentry *dentry,
--
2.5.5