Messages in this thread Patch in this message | | | Subject | [patch v3] vfs: fix sys_getcwd for detached mounts | From | Miklos Szeredi <> | Date | Mon, 23 Jun 2008 20:25:26 +0200 |
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I tested this one in various situations, and it appears to do what it's supposed to.
A somewhat analogous issue is if we have cwd (or fd) outside current->root. Should we add a prefix for that case as well? Perhaps a double slash?
-- From: Miklos Szeredi <mszeredi@suse.cz>
Currently getcwd(2) on a detached mount will give a garbled result:
> mkdir /mnt/foo > mount --bind /etc /mnt/foo > cd /mnt/foo/skel > umount -l /mnt/foo > /bin/pwd etcskel
After the patch the result will be "detached:skel".
Or if the root was mounted:
> mount --bind / /mnt/foo > cd /mnt/foo/etc > umount -l /mnt/foo > /bin/pwd /etc
After the patch the result will be "detached:etc".
Thanks to John Johansen for pointing out this bug.
v2: comment from Al Viro: use "detached:" prefix to differentiate it from attached paths.
v3: fix case when mounted dentry is root of the filesystem.
Reported-by: John Johansen <jjohansen@suse.de> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz> --- fs/dcache.c | 18 ++++++++++++++++-- 1 file changed, 16 insertions(+), 2 deletions(-)
Index: linux-2.6/fs/dcache.c =================================================================== --- linux-2.6.orig/fs/dcache.c 2008-06-23 19:34:21.000000000 +0200 +++ linux-2.6/fs/dcache.c 2008-06-23 20:15:09.000000000 +0200 @@ -1762,6 +1762,12 @@ static int prepend_name(char **buffer, i return prepend(buffer, buflen, name->name, name->len); } +static bool is_pseudo_root(struct dentry *dentry) +{ + return IS_ROOT(dentry) && + (dentry->d_name.len != 1 || dentry->d_name.name[0] != '/'); +} + /** * __d_path - return the path of a dentry * @path: the dentry/vfsmount to report @@ -1828,8 +1834,16 @@ char *__d_path(const struct path *path, global_root: retval += 1; /* hit the slash */ - if (prepend_name(&retval, &buflen, &dentry->d_name) != 0) - goto Elong; + + if (vfsmnt->mnt_ns != NULL || is_pseudo_root(dentry)) { + /* Attached, or pseudo filesystem with "foo:" prefix */ + if (prepend_name(&retval, &buflen, &dentry->d_name) != 0) + goto Elong; + } else { + /* Detached */ + if (prepend(&retval, &buflen, "detached:", 9) != 0) + goto Elong; + } root->mnt = vfsmnt; root->dentry = dentry; return retval;
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