On 8/28/2024 2:05 PM, Paul Moore wrote: > 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; Testing labeled NFS has always been a challenge for the somewhat limited resources available to the Smack project. I'll Ack the patch, but won't claim to have tested it. > 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. >
