On 2018/03/17 22:23, Goffredo Baroncelli wrote:
> On 03/15/2018 09:13 AM, Misono, Tomohiro wrote:
>> This is a preparetion work to allow normal user to call
>> "subvolume list/show".
>>
>> Signed-off-by: Tomohiro Misono <misono.tomohiro@xxxxxxxxxxxxxx>
>> ---
>> btrfs-list.c | 33 +++++++++++++++++++++++++++++++++
>> btrfs-list.h | 1 +
>> 2 files changed, 34 insertions(+)
>>
>> diff --git a/btrfs-list.c b/btrfs-list.c
>> index 50e5ce5f..88689a9d 100644
>> --- a/btrfs-list.c
>> +++ b/btrfs-list.c
>> @@ -958,6 +958,39 @@ out:
>> return 0;
>> }
>>
>> +/*
>> + * Check the permission for tree search ioctl by searching a key
>> + * which alwasys exists
>> + */
>> +int check_perm_for_tree_search(int fd)
>> +{
>
> In what this is different from '(getuid() == 0)' ?
> Which would be the cases where an error different from EPERM would be returned (other than the filesystem is not a BTRFS one )?
>
> I am not against to this kind of function. However with this implementation is not clear its behavior:
> - does it check if the user has enough privileges to perform a BTRFS_IOC_TREE_SEARCH
> or
> - does it check if BTRFS_IOC_TREE_SEARCH might return some error ?
>
> If the former, I would put this function into utils.[hc] checking only the [e]uid of the user. If the latter the name is confusing...
The reason I wrote this function is that the permission for BTRFS_IOC_TREE_SEARCH is
CAP_SYS_ADMIN and might not equal uid == 0.
However, it seems that get_euid() is simple and enough for btrfs-progs, so I will
use it instead of this function in next version.
Thanks,
Tomohiro Misono
>
>> + struct btrfs_ioctl_search_args args;
>> + struct btrfs_ioctl_search_key *sk = &args.key;
>> + int ret;
>> +
>> + memset(&args, 0, sizeof(args));
>> + sk->tree_id = BTRFS_ROOT_TREE_OBJECTID;
>> + sk->min_objectid = BTRFS_EXTENT_TREE_OBJECTID;
>> + sk->max_objectid = BTRFS_EXTENT_TREE_OBJECTID;
>> + sk->min_type = BTRFS_ROOT_ITEM_KEY;
>> + sk->max_type = BTRFS_ROOT_ITEM_KEY;
>> + sk->min_offset = 0;
>> + sk->max_offset = (u64)-1;
>> + sk->min_transid = 0;
>> + sk->max_transid = (u64)-1;
>> + sk->nr_items = 1;
>> + ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
>> +
>> + if (!ret)
>> + ret = 1;
>> + else if (ret < 0 && errno == EPERM)
>> + ret = 0;
>> + else
>> + ret = -errno;
>> +
>> + return ret;
>> +}
>> +
>> static int list_subvol_search(int fd, struct root_lookup *root_lookup)
>> {
>> int ret;
>> diff --git a/btrfs-list.h b/btrfs-list.h
>> index 6e5fc778..6225311d 100644
>> --- a/btrfs-list.h
>> +++ b/btrfs-list.h
>> @@ -176,5 +176,6 @@ char *btrfs_list_path_for_root(int fd, u64 root);
>> int btrfs_list_get_path_rootid(int fd, u64 *treeid);
>> int btrfs_get_subvol(int fd, struct root_info *the_ri);
>> int btrfs_get_toplevel_subvol(int fd, struct root_info *the_ri);
>> +int check_perm_for_tree_search(int fd);
>>
>> #endif
>>
>
>
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