The kpkeys_hardened_cred feature, when enabled, automatically protects credentials installed by commit_creds(). However, because override_creds() does not consume its argument, it is up to its callers to protect the credentials before calling override_creds(). This is done by calling protect_creds(), moving the credentials to a protected memory location.
In some cases, the credentials returned by prepare_creds() are passed to override_creds() as-is. In such situation where write access to the credentials is not needed, prepare_protected_creds() is used to avoid the copy incurred by a separate call to protect_creds(). This patch covers the main users of override_creds(), but it is not comprehensive. This patch is a no-op if kpkeys_hardened_cred isn't enabled. Signed-off-by: Kevin Brodsky <[email protected]> --- fs/aio.c | 2 +- fs/fuse/passthrough.c | 2 +- fs/nfs/nfs4idmap.c | 2 +- fs/nfsd/auth.c | 2 +- fs/nfsd/nfs4recover.c | 2 +- fs/nfsd/nfsfh.c | 2 +- fs/open.c | 2 +- fs/overlayfs/dir.c | 1 + fs/overlayfs/super.c | 2 +- 9 files changed, 9 insertions(+), 8 deletions(-) diff --git a/fs/aio.c b/fs/aio.c index 7fc7b6221312..7529399bb71d 100644 --- a/fs/aio.c +++ b/fs/aio.c @@ -1658,7 +1658,7 @@ static int aio_fsync(struct fsync_iocb *req, const struct iocb *iocb, if (unlikely(!req->file->f_op->fsync)) return -EINVAL; - req->creds = prepare_creds(); + req->creds = prepare_protected_creds(); if (!req->creds) return -ENOMEM; diff --git a/fs/fuse/passthrough.c b/fs/fuse/passthrough.c index 607ef735ad4a..4451651b1e51 100644 --- a/fs/fuse/passthrough.c +++ b/fs/fuse/passthrough.c @@ -248,7 +248,7 @@ int fuse_backing_open(struct fuse_conn *fc, struct fuse_backing_map *map) goto out_fput; fb->file = file; - fb->cred = prepare_creds(); + fb->cred = prepare_protected_creds(); refcount_set(&fb->count, 1); res = fuse_backing_id_alloc(fc, fb); diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c index 00932500fce4..6eef34b02513 100644 --- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -228,7 +228,7 @@ int nfs_idmap_init(void) set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags); cred->thread_keyring = keyring; cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING; - id_resolver_cache = cred; + id_resolver_cache = protect_creds(cred); return 0; failed_reg_legacy: diff --git a/fs/nfsd/auth.c b/fs/nfsd/auth.c index 4dc327e02456..09b377a97147 100644 --- a/fs/nfsd/auth.c +++ b/fs/nfsd/auth.c @@ -79,7 +79,7 @@ int nfsd_setuser(struct svc_cred *cred, struct svc_export *exp) else new->cap_effective = cap_raise_nfsd_set(new->cap_effective, new->cap_permitted); - put_cred(override_creds(new)); + put_cred(override_creds(protect_creds(new))); return 0; oom: diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c index 2231192ec33f..63ffa7936246 100644 --- a/fs/nfsd/nfs4recover.c +++ b/fs/nfsd/nfs4recover.c @@ -82,7 +82,7 @@ nfs4_save_creds(const struct cred **original_creds) new->fsuid = GLOBAL_ROOT_UID; new->fsgid = GLOBAL_ROOT_GID; - *original_creds = override_creds(new); + *original_creds = override_creds(protect_creds(new)); return 0; } diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c index 74cf1f4de174..887ee5adb2dc 100644 --- a/fs/nfsd/nfsfh.c +++ b/fs/nfsd/nfsfh.c @@ -223,7 +223,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct net *net, new->cap_effective = cap_raise_nfsd_set(new->cap_effective, new->cap_permitted); - put_cred(override_creds(new)); + put_cred(override_creds(protect_creds(new))); } else { error = nfsd_setuser_and_check_port(rqstp, cred, exp); if (error) diff --git a/fs/open.c b/fs/open.c index 9655158c3885..351ac9e86a15 100644 --- a/fs/open.c +++ b/fs/open.c @@ -461,7 +461,7 @@ static const struct cred *access_override_creds(void) * freeing. */ override_cred->non_rcu = 1; - return override_creds(override_cred); + return override_creds(protect_creds(override_cred)); } static int do_faccessat(int dfd, const char __user *filename, int mode, int flags) diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c index 70b8687dc45e..7e7d4f26198d 100644 --- a/fs/overlayfs/dir.c +++ b/fs/overlayfs/dir.c @@ -575,6 +575,7 @@ static const struct cred *ovl_setup_cred_for_create(struct dentry *dentry, * We must be called with creator creds already, otherwise we risk * leaking creds. */ + override_cred = protect_creds(override_cred); old_cred = override_creds(override_cred); WARN_ON_ONCE(old_cred != ovl_creds(dentry->d_sb)); diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index df85a76597e9..0a45760ff7ae 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1326,7 +1326,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc) err = -ENOMEM; if (!ofs->creator_cred) - ofs->creator_cred = cred = prepare_creds(); + ofs->creator_cred = cred = prepare_protected_creds(); else cred = (struct cred *)ofs->creator_cred; if (!cred) -- 2.47.0
