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author | Eric W. Biederman <ebiederm@xmission.com> | 2015-08-15 13:36:12 -0500 |
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committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-10-22 14:37:52 -0700 |
commit | 91397d567646df4ede8619beb678252e82fafb2a (patch) | |
tree | 36b5ea3f91d93d840b30dd2ea8b959cb87e8a3b4 | |
parent | ef5844a015293453e4031ad336e459729cfe3cd9 (diff) | |
download | lwn-91397d567646df4ede8619beb678252e82fafb2a.tar.gz lwn-91397d567646df4ede8619beb678252e82fafb2a.zip |
dcache: Handle escaped paths in prepend_path
commit cde93be45a8a90d8c264c776fab63487b5038a65 upstream.
A rename can result in a dentry that by walking up d_parent
will never reach it's mnt_root. For lack of a better term
I call this an escaped path.
prepend_path is called by four different functions __d_path,
d_absolute_path, d_path, and getcwd.
__d_path only wants to see paths are connected to the root it passes
in. So __d_path needs prepend_path to return an error.
d_absolute_path similarly wants to see paths that are connected to
some root. Escaped paths are not connected to any mnt_root so
d_absolute_path needs prepend_path to return an error greater
than 1. So escaped paths will be treated like paths on lazily
unmounted mounts.
getcwd needs to prepend "(unreachable)" so getcwd also needs
prepend_path to return an error.
d_path is the interesting hold out. d_path just wants to print
something, and does not care about the weird cases. Which raises
the question what should be printed?
Given that <escaped_path>/<anything> should result in -ENOENT I
believe it is desirable for escaped paths to be printed as empty
paths. As there are not really any meaninful path components when
considered from the perspective of a mount tree.
So tweak prepend_path to return an empty path with an new error
code of 3 when it encounters an escaped path.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r-- | fs/dcache.c | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index f1e801785976..17222fa5bdc6 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2534,6 +2534,8 @@ static int prepend_path(const struct path *path, struct dentry *dentry = path->dentry; struct vfsmount *vfsmnt = path->mnt; struct mount *mnt = real_mount(vfsmnt); + char *orig_buffer = *buffer; + int orig_len = *buflen; bool slash = false; int error = 0; @@ -2541,6 +2543,14 @@ static int prepend_path(const struct path *path, struct dentry * parent; if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { + /* Escaped? */ + if (dentry != vfsmnt->mnt_root) { + *buffer = orig_buffer; + *buflen = orig_len; + slash = false; + error = 3; + goto global_root; + } /* Global root? */ if (!mnt_has_parent(mnt)) goto global_root; |