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 <mszeredi@xxxxxxxxxx>
Cc: Tyler Hicks <tyhicks@xxxxxxxxxxxxx>
---
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
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