From: "Eric W. Biederman" <ebied...@xmission.com>
3.4.110-rc1 review patch. If anyone has any objections, please let me know.
------------------
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" <ebied...@xmission.com>
Signed-off-by: Al Viro <v...@zeniv.linux.org.uk>
Signed-off-by: Zefan Li <lize...@huawei.com>
---
fs/dcache.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/fs/dcache.c b/fs/dcache.c
index d071ea7..03eb2c2 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2518,6 +2518,8 @@ 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;
@@ -2525,6 +2527,14 @@ 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;
--
1.9.1
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