Quoting H. Peter Anvin (hpa@xxxxxxxxx): > Miklos Szeredi wrote: > > > > Andrew, please skip this patch, for now. > > > > Serge found a problem with the fsuid approach: setfsuid(nonzero) will > > remove filesystem related capabilities. So even if root is trying to > > set the "user=UID" flag on a mount, access to the target (and in case > > of bind, the source) is checked with user privileges. > > > > Root should be able to set this flag on any mountpoint, _regardless_ > > of permissions. > > > > Right, if you're using fsuid != 0, you're not running as root Sure, but what I'm not clear on is why, if I've done a prctl(PR_SET_KEEPCAPS, 1) before the setfsuid, I still lose the CAP_FS_MASK perms. I see the special case handling in cap_task_post_setuid(). I'm sure there was a reason for it, but this is a piece of the capability implementation I don't understand right now. I would send in a patch to make it honor current->keep_capabilities, but I have a feeling there was a good reason not to do so in the first place. > (fsuid is > the equivalent to euid for the filesystem.) If it were really the equivalent then I could keep my capabilities :) after changing it. > I fail to see how ruid should have *any* impact on mount(2). That seems > to be a design flaw. May be, but just using fsuid at this point stops me from enabling user mounts under /share if /share is chmod 000 (which it is). thanks, -serge - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
