TWx Linux Repository
bcf0d9d4b7
A problem similar to the one caught in commit 74dd7c97ea2a ("ecryptfs_rename():
verify that lower dentries are still OK after lock_rename()") exists for
unlink/rmdir as well.
Instead of playing with dget_parent() of underlying dentry of victim
and hoping it's the same as underlying dentry of our directory,
do the following:
* find the underlying dentry of victim
* find the underlying directory of victim's parent (stable
since the victim is ecryptfs dentry and inode of its parent is
held exclusive by the caller).
* lock the inode of dentry underlying the victim's parent
* check that underlying dentry of victim is still hashed and
has the right parent - it can be moved, but it can't be moved to/from
the directory we are holding exclusive. So while ->d_parent itself
might not be stable, the result of comparison is.
If the check passes, everything is fine - underlying directory is locked,
underlying victim is still a child of that directory and we can go ahead
and feed them to vfs_unlink(). As in the current mainline we need to
pin the underlying dentry of victim, so that it wouldn't go negative under
us, but that's the only temporary reference that needs to be grabbed there.
Underlying dentry of parent won't go away (it's pinned by the parent,
which is held by caller), so there's no need to grab it.
The same problem (with the same solution) exists for rmdir. Moreover,
rename gets simpler and more robust with the same "don't bother with
dget_parent()" approach.
Fixes: 74dd7c97ea2 "ecryptfs_rename(): verify that lower dentries are still OK after lock_rename()"
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.