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authorEric W. Biederman <ebiederm@xmission.com>2015-08-15 13:36:12 -0500
committerAl Viro <viro@zeniv.linux.org.uk>2015-08-21 02:34:36 -0400
commitcde93be45a8a90d8c264c776fab63487b5038a65 (patch)
tree95cfc85394609a68780c39750be10079cff8d966 /fs/dcache.c
parent6f179af88f60b32c2855e7f3e16ea8e336a7043f (diff)
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dcache: Handle escaped paths in prepend_path
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>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r--fs/dcache.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index 9b5fe50..e3b44ca 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2926,6 +2926,13 @@ restart:
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
struct mount *parent = ACCESS_ONCE(mnt->mnt_parent);
+ /* Escaped? */
+ if (dentry != vfsmnt->mnt_root) {
+ bptr = *buffer;
+ blen = *buflen;
+ error = 3;
+ break;
+ }
/* Global root? */
if (mnt != parent) {
dentry = ACCESS_ONCE(mnt->mnt_mountpoint);
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