[PATCH 05/10] nfsd: gate nfs3 setacl by argp->mask

[Jeff Layton <jlayton@kernel.org>]

From: Chris Mason <clm@meta.com>

nfsd3_proc_setacl() calls set_posix_acl() unconditionally for both
ACL_TYPE_ACCESS and ACL_TYPE_DEFAULT, passing argp->acl_access and
argp->acl_default verbatim. The NFSv3 ACL decoder only populates
those pointers when the corresponding mask bit is set:

    nfs3svc_decode_setaclargs()
      if (args->mask & NFS_ACL)    decode into acl_access
      if (args->mask & NFS_DFACL)  decode into acl_default
      /* otherwise the pointer stays NULL (pc_argzero) */

    nfsd3_proc_setacl()
      set_posix_acl(.., ACL_TYPE_ACCESS,  argp->acl_access)
      set_posix_acl(.., ACL_TYPE_DEFAULT, argp->acl_default)

set_posix_acl(idmap, dentry, type, NULL) is the VFS "remove this
ACL type" operation. A NULL pointer that means "the client did not
send this arm" is therefore indistinguishable from "the client
asked to remove this ACL". A SETACL with mask=NFS_ACL silently
drops the directory's default ACL; mask=0 drops both.

The sibling nfsd3_proc_getacl() already consults argp->mask before
touching each arm; mirror that in setacl.

Fix by wrapping each set_posix_acl() call in the matching mask bit
check and initializing error to 0 before inode_lock so that a
request with neither bit set leaves the on-disk ACLs untouched and
returns nfs_ok. The out_drop_lock path and the unconditional
posix_acl_release() at out: are preserved; both NULL-tolerate the
skipped arms.

Fixes: a257cdd0e217 ("[PATCH] NFSD: Add server support for NFSv3 ACLs.")
Assisted-by: kres:claude-opus-4-7
Signed-off-by: Chris Mason <clm@meta.com>
---
 fs/nfsd/nfs3acl.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/fs/nfsd/nfs3acl.c b/fs/nfsd/nfs3acl.c
index e87731380be8..a87f9d7f32be 100644
--- a/fs/nfsd/nfs3acl.c
+++ b/fs/nfsd/nfs3acl.c
@@ -105,12 +105,17 @@ static __be32 nfsd3_proc_setacl(struct svc_rqst *rqstp)
 
 	inode_lock(inode);
 
-	error = set_posix_acl(&nop_mnt_idmap, fh->fh_dentry, ACL_TYPE_ACCESS,
-			      argp->acl_access);
-	if (error)
-		goto out_drop_lock;
-	error = set_posix_acl(&nop_mnt_idmap, fh->fh_dentry, ACL_TYPE_DEFAULT,
-			      argp->acl_default);
+	error = 0;
+	if (argp->mask & NFS_ACL) {
+		error = set_posix_acl(&nop_mnt_idmap, fh->fh_dentry,
+				      ACL_TYPE_ACCESS, argp->acl_access);
+		if (error)
+			goto out_drop_lock;
+	}
+	if (argp->mask & NFS_DFACL) {
+		error = set_posix_acl(&nop_mnt_idmap, fh->fh_dentry,
+				      ACL_TYPE_DEFAULT, argp->acl_default);
+	}
 
 out_drop_lock:
 	inode_unlock(inode);

-- 
2.54.0