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authorEric W. Biederman <ebiederm@xmission.com>2015-08-15 13:36:12 -0500
committerZefan Li <lizefan@huawei.com>2015-10-22 09:20:08 +0800
commit652b4f2f20702cbb6cb7846a39af99d182c59764 (patch)
treec8797a21ba17b47bba2e264dc72a03dbd04c242a /fs
parent7a403328c381da57af51f57428f55d1388d233b2 (diff)
downloadlwn-652b4f2f20702cbb6cb7846a39af99d182c59764.tar.gz
lwn-652b4f2f20702cbb6cb7846a39af99d182c59764.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: Zefan Li <lizefan@huawei.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/dcache.c10
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/dcache.c b/fs/dcache.c
index d071ea768057..03eb2c2a7e5b 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;