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SubjectRe: [PATCH AUTOSEL 5.5 487/542] ceph: remove the extra slashes in the server path
On Fri, Feb 14, 2020 at 4:59 PM Sasha Levin <sashal@kernel.org> wrote:
>
> From: Xiubo Li <xiubli@redhat.com>
>
> [ Upstream commit 4fbc0c711b2464ee1551850b85002faae0b775d5 ]
>
> It's possible to pass the mount helper a server path that has more
> than one contiguous slash character. For example:
>
> $ mount -t ceph 192.168.195.165:40176:/// /mnt/cephfs/
>
> In the MDS server side the extra slashes of the server path will be
> treated as snap dir, and then we can get the following debug logs:
>
> ceph: mount opening path //
> ceph: open_root_inode opening '//'
> ceph: fill_trace 0000000059b8a3bc is_dentry 0 is_target 1
> ceph: alloc_inode 00000000dc4ca00b
> ceph: get_inode created new inode 00000000dc4ca00b 1.ffffffffffffffff ino 1
> ceph: get_inode on 1=1.ffffffffffffffff got 00000000dc4ca00b
>
> And then when creating any new file or directory under the mount
> point, we can hit the following BUG_ON in ceph_fill_trace():
>
> BUG_ON(ceph_snap(dir) != dvino.snap);
>
> Have the client ignore the extra slashes in the server path when
> mounting. This will also canonicalize the path, so that identical mounts
> can be consilidated.
>
> 1) "//mydir1///mydir//"
> 2) "/mydir1/mydir"
> 3) "/mydir1/mydir/"
>
> Regardless of the internal treatment of these paths, the kernel still
> stores the original string including the leading '/' for presentation
> to userland.
>
> URL: https://tracker.ceph.com/issues/42771
> Signed-off-by: Xiubo Li <xiubli@redhat.com>
> Reviewed-by: Jeff Layton <jlayton@kernel.org>
> Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
> Signed-off-by: Sasha Levin <sashal@kernel.org>
> ---
> fs/ceph/super.c | 122 ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 102 insertions(+), 20 deletions(-)
>
> diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> index 430dcf329723a..112927dbd2f20 100644
> --- a/fs/ceph/super.c
> +++ b/fs/ceph/super.c
> @@ -107,7 +107,6 @@ static int ceph_statfs(struct dentry *dentry, struct kstatfs *buf)
> return 0;
> }
>
> -
> static int ceph_sync_fs(struct super_block *sb, int wait)
> {
> struct ceph_fs_client *fsc = ceph_sb_to_client(sb);
> @@ -211,7 +210,6 @@ struct ceph_parse_opts_ctx {
>
> /*
> * Parse the source parameter. Distinguish the server list from the path.
> - * Internally we do not include the leading '/' in the path.
> *
> * The source will look like:
> * <server_spec>[,<server_spec>...]:[<path>]
> @@ -232,12 +230,15 @@ static int ceph_parse_source(struct fs_parameter *param, struct fs_context *fc)
>
> dev_name_end = strchr(dev_name, '/');
> if (dev_name_end) {
> - if (strlen(dev_name_end) > 1) {
> - kfree(fsopt->server_path);
> - fsopt->server_path = kstrdup(dev_name_end, GFP_KERNEL);
> - if (!fsopt->server_path)
> - return -ENOMEM;
> - }
> + kfree(fsopt->server_path);
> +
> + /*
> + * The server_path will include the whole chars from userland
> + * including the leading '/'.
> + */
> + fsopt->server_path = kstrdup(dev_name_end, GFP_KERNEL);
> + if (!fsopt->server_path)
> + return -ENOMEM;
> } else {
> dev_name_end = dev_name + strlen(dev_name);
> }
> @@ -461,6 +462,73 @@ static int strcmp_null(const char *s1, const char *s2)
> return strcmp(s1, s2);
> }
>
> +/**
> + * path_remove_extra_slash - Remove the extra slashes in the server path
> + * @server_path: the server path and could be NULL
> + *
> + * Return NULL if the path is NULL or only consists of "/", or a string
> + * without any extra slashes including the leading slash(es) and the
> + * slash(es) at the end of the server path, such as:
> + * "//dir1////dir2///" --> "dir1/dir2"
> + */
> +static char *path_remove_extra_slash(const char *server_path)
> +{
> + const char *path = server_path;
> + const char *cur, *end;
> + char *buf, *p;
> + int len;
> +
> + /* if the server path is omitted */
> + if (!path)
> + return NULL;
> +
> + /* remove all the leading slashes */
> + while (*path == '/')
> + path++;
> +
> + /* if the server path only consists of slashes */
> + if (*path == '\0')
> + return NULL;
> +
> + len = strlen(path);
> +
> + buf = kmalloc(len + 1, GFP_KERNEL);
> + if (!buf)
> + return ERR_PTR(-ENOMEM);
> +
> + end = path + len;
> + p = buf;
> + do {
> + cur = strchr(path, '/');
> + if (!cur)
> + cur = end;
> +
> + len = cur - path;
> +
> + /* including one '/' */
> + if (cur != end)
> + len += 1;
> +
> + memcpy(p, path, len);
> + p += len;
> +
> + while (cur <= end && *cur == '/')
> + cur++;
> + path = cur;
> + } while (path < end);
> +
> + *p = '\0';
> +
> + /*
> + * remove the last slash if there has and just to make sure that
> + * we will get something like "dir1/dir2"
> + */
> + if (*(--p) == '/')
> + *p = '\0';
> +
> + return buf;
> +}
> +
> static int compare_mount_options(struct ceph_mount_options *new_fsopt,
> struct ceph_options *new_opt,
> struct ceph_fs_client *fsc)
> @@ -468,6 +536,7 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
> struct ceph_mount_options *fsopt1 = new_fsopt;
> struct ceph_mount_options *fsopt2 = fsc->mount_options;
> int ofs = offsetof(struct ceph_mount_options, snapdir_name);
> + char *p1, *p2;
> int ret;
>
> ret = memcmp(fsopt1, fsopt2, ofs);
> @@ -480,9 +549,21 @@ static int compare_mount_options(struct ceph_mount_options *new_fsopt,
> ret = strcmp_null(fsopt1->mds_namespace, fsopt2->mds_namespace);
> if (ret)
> return ret;
> - ret = strcmp_null(fsopt1->server_path, fsopt2->server_path);
> +
> + p1 = path_remove_extra_slash(fsopt1->server_path);
> + if (IS_ERR(p1))
> + return PTR_ERR(p1);
> + p2 = path_remove_extra_slash(fsopt2->server_path);
> + if (IS_ERR(p2)) {
> + kfree(p1);
> + return PTR_ERR(p2);
> + }
> + ret = strcmp_null(p1, p2);
> + kfree(p1);
> + kfree(p2);
> if (ret)
> return ret;
> +
> ret = strcmp_null(fsopt1->fscache_uniq, fsopt2->fscache_uniq);
> if (ret)
> return ret;
> @@ -788,7 +869,6 @@ static void destroy_caches(void)
> ceph_fscache_unregister();
> }
>
> -
> /*
> * ceph_umount_begin - initiate forced umount. Tear down down the
> * mount, skipping steps that may hang while waiting for server(s).
> @@ -868,9 +948,6 @@ static struct dentry *open_root_dentry(struct ceph_fs_client *fsc,
> return root;
> }
>
> -
> -
> -
> /*
> * mount: join the ceph cluster, and open root directory.
> */
> @@ -885,7 +962,7 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc,
> mutex_lock(&fsc->client->mount_mutex);
>
> if (!fsc->sb->s_root) {
> - const char *path;
> + const char *path, *p;
> err = __ceph_open_session(fsc->client, started);
> if (err < 0)
> goto out;
> @@ -897,17 +974,22 @@ static struct dentry *ceph_real_mount(struct ceph_fs_client *fsc,
> goto out;
> }
>
> - if (!fsc->mount_options->server_path) {
> - path = "";
> - dout("mount opening path \\t\n");
> - } else {
> - path = fsc->mount_options->server_path + 1;
> - dout("mount opening path %s\n", path);
> + p = path_remove_extra_slash(fsc->mount_options->server_path);
> + if (IS_ERR(p)) {
> + err = PTR_ERR(p);
> + goto out;
> }
> + /* if the server path is omitted or just consists of '/' */
> + if (!p)
> + path = "";
> + else
> + path = p;
> + dout("mount opening path '%s'\n", path);
>
> ceph_fs_debugfs_init(fsc);
>
> root = open_root_dentry(fsc, path, started);
> + kfree(p);
> if (IS_ERR(root)) {
> err = PTR_ERR(root);
> goto out;

Hi Sasha,

This commit is buggy, the fix should land in 5.6-rc2. Please drop it
for now -- it would need to be taken together with "ceph: canonicalize
server path in place" or not backported at all.

Thanks,

Ilya

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