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SubjectRe: [PATCH] fuse: Ensure posix acls are translated outside of init_user_ns
ebiederm@xmission.com (Eric W. Biederman) writes:

> ebiederm@xmission.com (Eric W. Biederman) writes:
>
>> Ensure the translation happens by failing to read or write
>> posix acls when the filesystem has not indicated it supports
>> posix acls.
>>
>> This ensures that modern cached posix acl support is available
>> and used when dealing with posix acls. This is important
>> because only that path has the code to convernt the uids and
>> gids in posix acls into the user namespace of a fuse filesystem.
>>
>> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
>> ---
>
> ping.
>
> Miklos are you around where you can look at this?

Perhaps I got the wrong email address.

Ping?


>
>> Miklos after several attempts to handle this better last cycle. I
>> figure we should go with the stupid version for now. I think I know
>> how to do better but I don't want that to gate forward progress on
>> fully unprivileged fuse mounts. Especially as this is the last known
>> issue to deal with.
>>
>> fs/fuse/fuse_i.h | 1 +
>> fs/fuse/inode.c | 7 +++++++
>> fs/fuse/xattr.c | 43 +++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 51 insertions(+)
>>
>> diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
>> index f630951df8dc..5256ad333b05 100644
>> --- a/fs/fuse/fuse_i.h
>> +++ b/fs/fuse/fuse_i.h
>> @@ -985,6 +985,7 @@ ssize_t fuse_listxattr(struct dentry *entry, char *list, size_t size);
>> int fuse_removexattr(struct inode *inode, const char *name);
>> extern const struct xattr_handler *fuse_xattr_handlers[];
>> extern const struct xattr_handler *fuse_acl_xattr_handlers[];
>> +extern const struct xattr_handler *fuse_no_acl_xattr_handlers[];
>>
>> struct posix_acl;
>> struct posix_acl *fuse_get_acl(struct inode *inode, int type);
>> diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
>> index 1643043d4fe5..22c76cf8c2e3 100644
>> --- a/fs/fuse/inode.c
>> +++ b/fs/fuse/inode.c
>> @@ -1100,6 +1100,13 @@ static int fuse_fill_super(struct super_block *sb, void *data, int silent)
>> file->f_cred->user_ns != sb->s_user_ns)
>> goto err_fput;
>>
>> + /*
>> + * If we are not in the initial user namespace posix
>> + * acls must be translated.
>> + */
>> + if (sb->s_user_ns != &init_user_ns)
>> + sb->s_xattr = fuse_no_acl_xattr_handlers;
>> +
>> fc = kmalloc(sizeof(*fc), GFP_KERNEL);
>> err = -ENOMEM;
>> if (!fc)
>> diff --git a/fs/fuse/xattr.c b/fs/fuse/xattr.c
>> index 3caac46b08b0..433717640f78 100644
>> --- a/fs/fuse/xattr.c
>> +++ b/fs/fuse/xattr.c
>> @@ -192,6 +192,26 @@ static int fuse_xattr_set(const struct xattr_handler *handler,
>> return fuse_setxattr(inode, name, value, size, flags);
>> }
>>
>> +static bool no_xattr_list(struct dentry *dentry)
>> +{
>> + return false;
>> +}
>> +
>> +static int no_xattr_get(const struct xattr_handler *handler,
>> + struct dentry *dentry, struct inode *inode,
>> + const char *name, void *value, size_t size)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +
>> +static int no_xattr_set(const struct xattr_handler *handler,
>> + struct dentry *dentry, struct inode *nodee,
>> + const char *name, const void *value,
>> + size_t size, int flags)
>> +{
>> + return -EOPNOTSUPP;
>> +}
>> +
>> static const struct xattr_handler fuse_xattr_handler = {
>> .prefix = "",
>> .get = fuse_xattr_get,
>> @@ -209,3 +229,26 @@ const struct xattr_handler *fuse_acl_xattr_handlers[] = {
>> &fuse_xattr_handler,
>> NULL
>> };
>> +
>> +static const struct xattr_handler fuse_no_acl_access_xattr_handler = {
>> + .name = XATTR_NAME_POSIX_ACL_ACCESS,
>> + .flags = ACL_TYPE_ACCESS,
>> + .list = no_xattr_list,
>> + .get = no_xattr_get,
>> + .set = no_xattr_set,
>> +};
>> +
>> +static const struct xattr_handler fuse_no_acl_default_xattr_handler = {
>> + .name = XATTR_NAME_POSIX_ACL_DEFAULT,
>> + .flags = ACL_TYPE_ACCESS,
>> + .list = no_xattr_list,
>> + .get = no_xattr_get,
>> + .set = no_xattr_set,
>> +};
>> +
>> +const struct xattr_handler *fuse_no_acl_xattr_handlers[] = {
>> + &fuse_no_acl_access_xattr_handler,
>> + &fuse_no_acl_default_xattr_handler,
>> + &fuse_xattr_handler,
>> + NULL
>> +};

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