On 9/23/14 7:49 AM, Chris Mason wrote: > On 09/23/2014 01:40 AM, Qu Wenruo wrote: >> [BUG] >> Originally when mount btrfs with "-o subvol=" mount option, btrfs will >> lose all security lable. >> And if the btrfs fs is mounted somewhere else, due to the lost of >> security lable, SELinux will refuse to mount since the same super block >> is being mounted using different security lable. >> >> [REPRODUCER] >> With SELinux enabled: >> #mkfs -t btrfs /dev/sda5 >> #mount -o context=system_u:object_r:nfs_t:s0 /dev/sda5 /mnt/btrfs >> #btrfs subvolume create /mnt/btrfs/subvol >> #mount -o subvol=subvol,context=system_u:object_r:nfs_t:s0 /dev/sda5 >> /mnt/test >> >> kernel message: >> SELinux: mount invalid. Same superblock, different security settings >> for (dev sda5, type btrfs) >> >> [REASON] >> This happens because btrfs will call vfs_kern_mount() and then >> mount_subtree() to handle subvolume name lookup. >> First mount will cut off all the security lables and when it comes to >> the second vfs_kern_mount(), it has no security label now. >> >> [FIX] >> This patch will makes btrfs behavior much more like nfs, >> which has the type flag FS_BINARY_MOUNTDATA, >> making btrfs handles the security label internally. >> So security label will be set in the real mount time and won't lose >> label when use with "subvol=" mount option. > > Thanks for working on this. Eric Sandeen (cc'd) was trying out > something similar recently, so I want to make sure this doesn't conflict > with his ideas.
My ideas didn't get very far. ;) What I was after was a way for multiple subvolumes to have unique contexts. It looks like this might do the trick, as long as they are mounted on a unique mount point. Would this allow "subvolume create" to take a context, so that everything under /mnt/btrfs/subvol/ has a unique subvol-wide context? thanks, -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
