On Fri, Sep 23, 2016 at 08:44:14PM +0530, Pranith Kumar Karampuri wrote: > On Fri, Sep 23, 2016 at 6:12 PM, Jeff Darcy <jdarcy@xxxxxxxxxx> wrote: > > > > Jiffin found an interesting problem in posix xlator where we have never > > been > > > using setfsuid/gid ( http://review.gluster.org/#/c/15545/ ), what I am > > > seeing regressions after this is, if the files are created using non-root > > > user then the file creation fails because that user doesn't have > > permissions > > > to create the gfid-link. So it seems like the correct way forward for > > this > > > patch is to write wrappers around sys_<syscall> to do setfsuid/gid do the > > > actual operation requested and then set it back to old uid/gid and then > > do > > > the internal operations. I am planning to write posix_sys_<syscall>() to > > do > > > the same, may be a macro? > > > > Kind of an aside, but I'd prefer to see a lot fewer macros in our code. > > They're not type-safe, and multi-line macros often mess up line numbers for > > debugging or error messages. IMO it's better to use functions whenever > > possible, and usually to let the compiler worry about how/when to inline. > > > > > I need inputs from you guys to let me know if I am on the right path and > > if > > > you see any issues with this approach. > > > > I think there's a bit of an interface problem here. The sys_xxx wrappers > > don't have arguments that point to the current frame, so how would they get > > the correct uid/gid? We could add arguments to each function, but then > > we'd have to modify every call. This includes internal calls which don't > > have a frame to pass, so I guess they'd have to pass NULL. Alternatively, > > we could create a parallel set of functions with frame pointers. Contrary > > to what I just said above, this might be a case where macros make sense: > > > > int > > sys_writev_fp (call_frame_t *frame, int fd, void *buf, size_t len) > > { > > if (frame) { setfsuid(...) ... } > > int ret = writev (fd, buf, len); > > if (frame) { setfsuid(...) ... } > > return ret; > > } > > #define sys_writev(fd,buf,len) sys_writev_fp (NULL, fd, buf, len) > > > > That way existing callers don't have to change, but posix can use the > > extended versions to get the right setfsuid behavior. > > > > > After trying to do these modifications to test things out, I am now under > the impression to remove setfsuid/gid altogether and depend on posix-acl > for permission checks. It seems too cumbersome as the operations more often > than not happen on files inside .glusterfs and non-root users/groups don't > have permissions at all to access files in that directory. But the files under .glusterfs are hardlinks. Except for creation and removal, should the users not have access to read/write and update attributes and xattrs? I would prefer to rely on the VFS permission checking on the bricks, and not bother with the posix-acl xlator when the filesystem on the brick supports POSIX ACLs. Niels
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