On Wed, Aug 28, 2024 at 3:51 PM Scott Mayhew <smayhew@xxxxxxxxxx> wrote: > > Marek Gresko reports that the root user on an NFS client is able to > change the security labels on files on an NFS filesystem that is > exported with root squashing enabled. > > The end of the kerneldoc comment for __vfs_setxattr_noperm() states: > > * This function requires the caller to lock the inode's i_mutex before it > * is executed. It also assumes that the caller will make the appropriate > * permission checks. > > nfsd_setattr() does do permissions checking via fh_verify() and > nfsd_permission(), but those don't do all the same permissions checks > that are done by security_inode_setxattr() and its related LSM hooks do. > > Since nfsd_setattr() is the only consumer of security_inode_setsecctx(), > simplest solution appears to be to replace the call to > __vfs_setxattr_noperm() with a call to __vfs_setxattr_locked(). This > fixes the above issue and has the added benefit of causing nfsd to > recall conflicting delegations on a file when a client tries to change > its security label. > > Reported-by: Marek Gresko <marek.gresko@xxxxxxxxxxxxxx> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=218809 > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx> > --- > security/selinux/hooks.c | 4 ++-- > security/smack/smack_lsm.c | 4 ++-- > 2 files changed, 4 insertions(+), 4 deletions(-) Thanks Scott, this looks good to me, but since it touches Smack too I'd also like to get Casey's ACK on this patch; if for some reason we don't hear from Casey after a bit I'll go ahead and merge it. Speaking of merging, since this touches both SELinux and Smack I'll likely pull this in via the LSM tree, with a marking for the stable kernels, if anyone has any objections to that please let me know. -- paul-moore.com
