Merge tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull cred guard updates from Christian Brauner:
 "This contains substantial credential infrastructure improvements
  adding guard-based credential management that simplifies code and
  eliminates manual reference counting in many subsystems.

  Features:

   - Kernel Credential Guards

     Add with_kernel_creds() and scoped_with_kernel_creds() guards that
     allow using the kernel credentials without allocating and copying
     them. This was requested by Linus after seeing repeated
     prepare_kernel_creds() calls that duplicate the kernel credentials
     only to drop them again later.

     The new guards completely avoid the allocation and never expose the
     temporary variable to hold the kernel credentials anywhere in
     callers.

   - Generic Credential Guards

     Add scoped_with_creds() guards for the common override_creds() and
     revert_creds() pattern. This builds on earlier work that made
     override_creds()/revert_creds() completely reference count free.

   - Prepare Credential Guards

     Add prepare credential guards for the more complex pattern of
     preparing a new set of credentials and overriding the current
     credentials with them:
      - prepare_creds()
      - modify new creds
      - override_creds()
      - revert_creds()
      - put_cred()

  Cleanups:

   - Make init_cred static since it should not be directly accessed

   - Add kernel_cred() helper to properly access the kernel credentials

   - Fix scoped_class() macro that was introduced two cycles ago

   - coredump: split out do_coredump() from vfs_coredump() for cleaner
     credential handling

   - coredump: move revert_cred() before coredump_cleanup()

   - coredump: mark struct mm_struct as const

   - coredump: pass struct linux_binfmt as const

   - sev-dev: use guard for path"

* tag 'kernel-6.19-rc1.cred' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (36 commits)
  trace: use override credential guard
  trace: use prepare credential guard
  coredump: use override credential guard
  coredump: use prepare credential guard
  coredump: split out do_coredump() from vfs_coredump()
  coredump: mark struct mm_struct as const
  coredump: pass struct linux_binfmt as const
  coredump: move revert_cred() before coredump_cleanup()
  sev-dev: use override credential guards
  sev-dev: use prepare credential guard
  sev-dev: use guard for path
  cred: add prepare credential guard
  net/dns_resolver: use credential guards in dns_query()
  cgroup: use credential guards in cgroup_attach_permissions()
  act: use credential guards in acct_write_process()
  smb: use credential guards in cifs_get_spnego_key()
  nfs: use credential guards in nfs_idmap_get_key()
  nfs: use credential guards in nfs_local_call_write()
  nfs: use credential guards in nfs_local_call_read()
  erofs: use credential guards
  ...

8 files changed, 185 insertions, 182 deletions

diff --git a/fs/aio.c b/fs/aio.c
index 5bc133386407..0a23a8c0717f 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1640,10 +1640,10 @@ static int aio_write(struct kiocb *req, const struct iocb *iocb,
 static void aio_fsync_work(struct work_struct *work)
 {
 	struct aio_kiocb *iocb = container_of(work, struct aio_kiocb, fsync.work);
-	const struct cred *old_cred = override_creds(iocb->fsync.creds);
 
-	iocb->ki_res.res = vfs_fsync(iocb->fsync.file, iocb->fsync.datasync);
-	revert_creds(old_cred);
+	scoped_with_creds(iocb->fsync.creds)
+		iocb->ki_res.res = vfs_fsync(iocb->fsync.file, iocb->fsync.datasync);
+
 	put_cred(iocb->fsync.creds);
 	iocb_put(iocb);
 }
diff --git a/fs/backing-file.c b/fs/backing-file.c
index 2a86bb6fcd13..45da8600d564 100644
--- a/fs/backing-file.c
+++ b/fs/backing-file.c
@@ -157,13 +157,37 @@ static int backing_aio_init_wq(struct kiocb *iocb)
 	return sb_init_dio_done_wq(sb);
 }
 
+static int do_backing_file_read_iter(struct file *file, struct iov_iter *iter,
+				     struct kiocb *iocb, int flags)
+{
+	struct backing_aio *aio = NULL;
+	int ret;
+
+	if (is_sync_kiocb(iocb)) {
+		rwf_t rwf = iocb_to_rw_flags(flags);
+
+		return vfs_iter_read(file, iter, &iocb->ki_pos, rwf);
+	}
+
+	aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
+	if (!aio)
+		return -ENOMEM;
+
+	aio->orig_iocb = iocb;
+	kiocb_clone(&aio->iocb, iocb, get_file(file));
+	aio->iocb.ki_complete = backing_aio_rw_complete;
+	refcount_set(&aio->ref, 2);
+	ret = vfs_iocb_iter_read(file, &aio->iocb, iter);
+	backing_aio_put(aio);
+	if (ret != -EIOCBQUEUED)
+		backing_aio_cleanup(aio, ret);
+	return ret;
+}
 
 ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 			       struct kiocb *iocb, int flags,
 			       struct backing_file_ctx *ctx)
 {
-	struct backing_aio *aio = NULL;
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
@@ -176,41 +200,57 @@ ssize_t backing_file_read_iter(struct file *file, struct iov_iter *iter,
 	    !(file->f_mode & FMODE_CAN_ODIRECT))
 		return -EINVAL;
 
-	old_cred = override_creds(ctx->cred);
+	scoped_with_creds(ctx->cred)
+		ret = do_backing_file_read_iter(file, iter, iocb, flags);
+
+	if (ctx->accessed)
+		ctx->accessed(iocb->ki_filp);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(backing_file_read_iter);
+
+static int do_backing_file_write_iter(struct file *file, struct iov_iter *iter,
+				      struct kiocb *iocb, int flags,
+				      void (*end_write)(struct kiocb *, ssize_t))
+{
+	struct backing_aio *aio;
+	int ret;
+
 	if (is_sync_kiocb(iocb)) {
 		rwf_t rwf = iocb_to_rw_flags(flags);
 
-		ret = vfs_iter_read(file, iter, &iocb->ki_pos, rwf);
-	} else {
-		ret = -ENOMEM;
-		aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
-		if (!aio)
-			goto out;
-
-		aio->orig_iocb = iocb;
-		kiocb_clone(&aio->iocb, iocb, get_file(file));
-		aio->iocb.ki_complete = backing_aio_rw_complete;
-		refcount_set(&aio->ref, 2);
-		ret = vfs_iocb_iter_read(file, &aio->iocb, iter);
-		backing_aio_put(aio);
-		if (ret != -EIOCBQUEUED)
-			backing_aio_cleanup(aio, ret);
+		ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf);
+		if (end_write)
+			end_write(iocb, ret);
+		return ret;
 	}
-out:
-	revert_creds(old_cred);
 
-	if (ctx->accessed)
-		ctx->accessed(iocb->ki_filp);
+	ret = backing_aio_init_wq(iocb);
+	if (ret)
+		return ret;
+
+	aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
+	if (!aio)
+		return -ENOMEM;
 
+	aio->orig_iocb = iocb;
+	aio->end_write = end_write;
+	kiocb_clone(&aio->iocb, iocb, get_file(file));
+	aio->iocb.ki_flags = flags;
+	aio->iocb.ki_complete = backing_aio_queue_completion;
+	refcount_set(&aio->ref, 2);
+	ret = vfs_iocb_iter_write(file, &aio->iocb, iter);
+	backing_aio_put(aio);
+	if (ret != -EIOCBQUEUED)
+		backing_aio_cleanup(aio, ret);
 	return ret;
 }
-EXPORT_SYMBOL_GPL(backing_file_read_iter);
 
 ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 				struct kiocb *iocb, int flags,
 				struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(file->f_mode & FMODE_BACKING)))
@@ -227,40 +267,8 @@ ssize_t backing_file_write_iter(struct file *file, struct iov_iter *iter,
 	    !(file->f_mode & FMODE_CAN_ODIRECT))
 		return -EINVAL;
 
-	old_cred = override_creds(ctx->cred);
-	if (is_sync_kiocb(iocb)) {
-		rwf_t rwf = iocb_to_rw_flags(flags);
-
-		ret = vfs_iter_write(file, iter, &iocb->ki_pos, rwf);
-		if (ctx->end_write)
-			ctx->end_write(iocb, ret);
-	} else {
-		struct backing_aio *aio;
-
-		ret = backing_aio_init_wq(iocb);
-		if (ret)
-			goto out;
-
-		ret = -ENOMEM;
-		aio = kmem_cache_zalloc(backing_aio_cachep, GFP_KERNEL);
-		if (!aio)
-			goto out;
-
-		aio->orig_iocb = iocb;
-		aio->end_write = ctx->end_write;
-		kiocb_clone(&aio->iocb, iocb, get_file(file));
-		aio->iocb.ki_flags = flags;
-		aio->iocb.ki_complete = backing_aio_queue_completion;
-		refcount_set(&aio->ref, 2);
-		ret = vfs_iocb_iter_write(file, &aio->iocb, iter);
-		backing_aio_put(aio);
-		if (ret != -EIOCBQUEUED)
-			backing_aio_cleanup(aio, ret);
-	}
-out:
-	revert_creds(old_cred);
-
-	return ret;
+	scoped_with_creds(ctx->cred)
+		return do_backing_file_write_iter(file, iter, iocb, flags, ctx->end_write);
 }
 EXPORT_SYMBOL_GPL(backing_file_write_iter);
 
@@ -269,15 +277,13 @@ ssize_t backing_file_splice_read(struct file *in, struct kiocb *iocb,
 				 unsigned int flags,
 				 struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(in->f_mode & FMODE_BACKING)))
 		return -EIO;
 
-	old_cred = override_creds(ctx->cred);
-	ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags);
-	revert_creds(old_cred);
+	scoped_with_creds(ctx->cred)
+		ret = vfs_splice_read(in, &iocb->ki_pos, pipe, len, flags);
 
 	if (ctx->accessed)
 		ctx->accessed(iocb->ki_filp);
@@ -291,7 +297,6 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 				  size_t len, unsigned int flags,
 				  struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	ssize_t ret;
 
 	if (WARN_ON_ONCE(!(out->f_mode & FMODE_BACKING)))
@@ -304,11 +309,11 @@ ssize_t backing_file_splice_write(struct pipe_inode_info *pipe,
 	if (ret)
 		return ret;
 
-	old_cred = override_creds(ctx->cred);
-	file_start_write(out);
-	ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);
-	file_end_write(out);
-	revert_creds(old_cred);
+	scoped_with_creds(ctx->cred) {
+		file_start_write(out);
+		ret = out->f_op->splice_write(pipe, out, &iocb->ki_pos, len, flags);
+		file_end_write(out);
+	}
 
 	if (ctx->end_write)
 		ctx->end_write(iocb, ret);
@@ -320,7 +325,6 @@ EXPORT_SYMBOL_GPL(backing_file_splice_write);
 int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 		      struct backing_file_ctx *ctx)
 {
-	const struct cred *old_cred;
 	struct file *user_file = vma->vm_file;
 	int ret;
 
@@ -332,9 +336,8 @@ int backing_file_mmap(struct file *file, struct vm_area_struct *vma,
 
 	vma_set_file(vma, file);
 
-	old_cred = override_creds(ctx->cred);
-	ret = vfs_mmap(vma->vm_file, vma);
-	revert_creds(old_cred);
+	scoped_with_creds(ctx->cred)
+		ret = vfs_mmap(vma->vm_file, vma);
 
 	if (ctx->accessed)
 		ctx->accessed(user_file);
diff --git a/fs/binfmt_misc.c b/fs/binfmt_misc.c
index a8b1d79e4af0..d7aec5b87c2b 100644
--- a/fs/binfmt_misc.c
+++ b/fs/binfmt_misc.c
@@ -782,8 +782,6 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		return PTR_ERR(e);
 
 	if (e->flags & MISC_FMT_OPEN_FILE) {
-		const struct cred *old_cred;
-
 		/*
 		 * Now that we support unprivileged binfmt_misc mounts make
 		 * sure we use the credentials that the register @file was
@@ -791,9 +789,8 @@ static ssize_t bm_register_write(struct file *file, const char __user *buffer,
 		 * didn't matter much as only a privileged process could open
 		 * the register file.
 		 */
-		old_cred = override_creds(file->f_cred);
-		f = open_exec(e->interpreter);
-		revert_creds(old_cred);
+		scoped_with_creds(file->f_cred)
+			f = open_exec(e->interpreter);
 		if (IS_ERR(f)) {
 			pr_notice("register: failed to install interpreter file %s\n",
 				 e->interpreter);
diff --git a/fs/coredump.c b/fs/coredump.c
index 5c1c381ee380..fe4099e0530b 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -1036,7 +1036,7 @@ static bool coredump_pipe(struct core_name *cn, struct coredump_params *cprm,
 
 static bool coredump_write(struct core_name *cn,
 			  struct coredump_params *cprm,
-			  struct linux_binfmt *binfmt)
+			  const struct linux_binfmt *binfmt)
 {
 
 	if (dump_interrupted())
@@ -1086,119 +1086,119 @@ static inline bool coredump_skip(const struct coredump_params *cprm,
 	return false;
 }
 
-void vfs_coredump(const kernel_siginfo_t *siginfo)
+static void do_coredump(struct core_name *cn, struct coredump_params *cprm,
+			size_t **argv, int *argc, const struct linux_binfmt *binfmt)
 {
-	struct cred *cred __free(put_cred) = NULL;
-	size_t *argv __free(kfree) = NULL;
-	struct core_state core_state;
-	struct core_name cn;
-	struct mm_struct *mm = current->mm;
-	struct linux_binfmt *binfmt = mm->binfmt;
-	const struct cred *old_cred;
-	int argc = 0;
-	struct coredump_params cprm = {
-		.siginfo = siginfo,
-		.limit = rlimit(RLIMIT_CORE),
-		/*
-		 * We must use the same mm->flags while dumping core to avoid
-		 * inconsistency of bit flags, since this flag is not protected
-		 * by any locks.
-		 *
-		 * Note that we only care about MMF_DUMP* flags.
-		 */
-		.mm_flags = __mm_flags_get_dumpable(mm),
-		.vma_meta = NULL,
-		.cpu = raw_smp_processor_id(),
-	};
-
-	audit_core_dumps(siginfo->si_signo);
-
-	if (coredump_skip(&cprm, binfmt))
-		return;
-
-	cred = prepare_creds();
-	if (!cred)
-		return;
-	/*
-	 * We cannot trust fsuid as being the "true" uid of the process
-	 * nor do we know its entire history. We only know it was tainted
-	 * so we dump it as root in mode 2, and only into a controlled
-	 * environment (pipe handler or fully qualified path).
-	 */
-	if (coredump_force_suid_safe(&cprm))
-		cred->fsuid = GLOBAL_ROOT_UID;
-
-	if (coredump_wait(siginfo->si_signo, &core_state) < 0)
-		return;
-
-	old_cred = override_creds(cred);
-
-	if (!coredump_parse(&cn, &cprm, &argv, &argc)) {
+	if (!coredump_parse(cn, cprm, argv, argc)) {
 		coredump_report_failure("format_corename failed, aborting core");
-		goto close_fail;
+		return;
 	}
 
-	switch (cn.core_type) {
+	switch (cn->core_type) {
 	case COREDUMP_FILE:
-		if (!coredump_file(&cn, &cprm, binfmt))
-			goto close_fail;
+		if (!coredump_file(cn, cprm, binfmt))
+			return;
 		break;
 	case COREDUMP_PIPE:
-		if (!coredump_pipe(&cn, &cprm, argv, argc))
-			goto close_fail;
+		if (!coredump_pipe(cn, cprm, *argv, *argc))
+			return;
 		break;
 	case COREDUMP_SOCK_REQ:
 		fallthrough;
 	case COREDUMP_SOCK:
-		if (!coredump_socket(&cn, &cprm))
-			goto close_fail;
+		if (!coredump_socket(cn, cprm))
+			return;
 		break;
 	default:
 		WARN_ON_ONCE(true);
-		goto close_fail;
+		return;
 	}
 
 	/* Don't even generate the coredump. */
-	if (cn.mask & COREDUMP_REJECT)
-		goto close_fail;
+	if (cn->mask & COREDUMP_REJECT)
+		return;
 
 	/* get us an unshared descriptor table; almost always a no-op */
 	/* The cell spufs coredump code reads the file descriptor tables */
 	if (unshare_files())
-		goto close_fail;
+		return;
 
-	if ((cn.mask & COREDUMP_KERNEL) && !coredump_write(&cn, &cprm, binfmt))
-		goto close_fail;
+	if ((cn->mask & COREDUMP_KERNEL) && !coredump_write(cn, cprm, binfmt))
+		return;
 
-	coredump_sock_shutdown(cprm.file);
+	coredump_sock_shutdown(cprm->file);
 
 	/* Let the parent know that a coredump was generated. */
-	if (cn.mask & COREDUMP_USERSPACE)
-		cn.core_dumped = true;
+	if (cn->mask & COREDUMP_USERSPACE)
+		cn->core_dumped = true;
 
 	/*
 	 * When core_pipe_limit is set we wait for the coredump server
 	 * or usermodehelper to finish before exiting so it can e.g.,
 	 * inspect /proc/<pid>.
 	 */
-	if (cn.mask & COREDUMP_WAIT) {
-		switch (cn.core_type) {
+	if (cn->mask & COREDUMP_WAIT) {
+		switch (cn->core_type) {
 		case COREDUMP_PIPE:
-			wait_for_dump_helpers(cprm.file);
+			wait_for_dump_helpers(cprm->file);
 			break;
 		case COREDUMP_SOCK_REQ:
 			fallthrough;
 		case COREDUMP_SOCK:
-			coredump_sock_wait(cprm.file);
+			coredump_sock_wait(cprm->file);
 			break;
 		default:
 			break;
 		}
 	}
+}
+
+void vfs_coredump(const kernel_siginfo_t *siginfo)
+{
+	size_t *argv __free(kfree) = NULL;
+	struct core_state core_state;
+	struct core_name cn;
+	const struct mm_struct *mm = current->mm;
+	const struct linux_binfmt *binfmt = mm->binfmt;
+	int argc = 0;
+	struct coredump_params cprm = {
+		.siginfo = siginfo,
+		.limit = rlimit(RLIMIT_CORE),
+		/*
+		 * We must use the same mm->flags while dumping core to avoid
+		 * inconsistency of bit flags, since this flag is not protected
+		 * by any locks.
+		 *
+		 * Note that we only care about MMF_DUMP* flags.
+		 */
+		.mm_flags = __mm_flags_get_dumpable(mm),
+		.vma_meta = NULL,
+		.cpu = raw_smp_processor_id(),
+	};
+
+	audit_core_dumps(siginfo->si_signo);
+
+	if (coredump_skip(&cprm, binfmt))
+		return;
+
+	CLASS(prepare_creds, cred)();
+	if (!cred)
+		return;
+	/*
+	 * We cannot trust fsuid as being the "true" uid of the process
+	 * nor do we know its entire history. We only know it was tainted
+	 * so we dump it as root in mode 2, and only into a controlled
+	 * environment (pipe handler or fully qualified path).
+	 */
+	if (coredump_force_suid_safe(&cprm))
+		cred->fsuid = GLOBAL_ROOT_UID;
+
+	if (coredump_wait(siginfo->si_signo, &core_state) < 0)
+		return;
 
-close_fail:
+	scoped_with_creds(cred)
+		do_coredump(&cn, &cprm, &argv, &argc, binfmt);
 	coredump_cleanup(&cn, &cprm);
-	revert_creds(old_cred);
 	return;
 }
 
diff --git a/fs/erofs/fileio.c b/fs/erofs/fileio.c
index b7b3432a9882..d27938435b2f 100644
--- a/fs/erofs/fileio.c
+++ b/fs/erofs/fileio.c
@@ -47,7 +47,6 @@ static void erofs_fileio_ki_complete(struct kiocb *iocb, long ret)
 
 static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq)
 {
-	const struct cred *old_cred;
 	struct iov_iter iter;
 	int ret;
 
@@ -61,9 +60,8 @@ static void erofs_fileio_rq_submit(struct erofs_fileio_rq *rq)
 		rq->iocb.ki_flags = IOCB_DIRECT;
 	iov_iter_bvec(&iter, ITER_DEST, rq->bvecs, rq->bio.bi_vcnt,
 		      rq->bio.bi_iter.bi_size);
-	old_cred = override_creds(rq->iocb.ki_filp->f_cred);
-	ret = vfs_iocb_iter_read(rq->iocb.ki_filp, &rq->iocb, &iter);
-	revert_creds(old_cred);
+	scoped_with_creds(rq->iocb.ki_filp->f_cred)
+		ret = vfs_iocb_iter_read(rq->iocb.ki_filp, &rq->iocb, &iter);
 	if (ret != -EIOCBQUEUED)
 		erofs_fileio_ki_complete(&rq->iocb, ret);
 }
diff --git a/fs/nfs/localio.c b/fs/nfs/localio.c
index 656976b4f42c..49ed90c6b9f2 100644
--- a/fs/nfs/localio.c
+++ b/fs/nfs/localio.c
@@ -615,18 +615,12 @@ static void nfs_local_read_aio_complete(struct kiocb *kiocb, long ret)
 	nfs_local_pgio_aio_complete(iocb); /* Calls nfs_local_read_aio_complete_work */
 }
 
-static void nfs_local_call_read(struct work_struct *work)
+static void do_nfs_local_call_read(struct nfs_local_kiocb *iocb, struct file *filp)
 {
-	struct nfs_local_kiocb *iocb =
-		container_of(work, struct nfs_local_kiocb, work);
-	struct file *filp = iocb->kiocb.ki_filp;
-	const struct cred *save_cred;
 	bool force_done = false;
 	ssize_t status;
 	int n_iters;
 
-	save_cred = override_creds(filp->f_cred);
-
 	n_iters = atomic_read(&iocb->n_iters);
 	for (int i = 0; i < n_iters ; i++) {
 		if (iocb->iter_is_dio_aligned[i]) {
@@ -649,8 +643,16 @@ static void nfs_local_call_read(struct work_struct *work)
 			}
 		}
 	}
+}
 
-	revert_creds(save_cred);
+static void nfs_local_call_read(struct work_struct *work)
+{
+	struct nfs_local_kiocb *iocb =
+		container_of(work, struct nfs_local_kiocb, work);
+	struct file *filp = iocb->kiocb.ki_filp;
+
+	scoped_with_creds(filp->f_cred)
+		do_nfs_local_call_read(iocb, filp);
 }
 
 static int
@@ -820,20 +822,13 @@ static void nfs_local_write_aio_complete(struct kiocb *kiocb, long ret)
 	nfs_local_pgio_aio_complete(iocb); /* Calls nfs_local_write_aio_complete_work */
 }
 
-static void nfs_local_call_write(struct work_struct *work)
+static ssize_t do_nfs_local_call_write(struct nfs_local_kiocb *iocb,
+				       struct file *filp)
 {
-	struct nfs_local_kiocb *iocb =
-		container_of(work, struct nfs_local_kiocb, work);
-	struct file *filp = iocb->kiocb.ki_filp;
-	unsigned long old_flags = current->flags;
-	const struct cred *save_cred;
 	bool force_done = false;
 	ssize_t status;
 	int n_iters;
 
-	current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
-	save_cred = override_creds(filp->f_cred);
-
 	file_start_write(filp);
 	n_iters = atomic_read(&iocb->n_iters);
 	for (int i = 0; i < n_iters ; i++) {
@@ -859,7 +854,22 @@ static void nfs_local_call_write(struct work_struct *work)
 	}
 	file_end_write(filp);
 
-	revert_creds(save_cred);
+	return status;
+}
+
+static void nfs_local_call_write(struct work_struct *work)
+{
+	struct nfs_local_kiocb *iocb =
+		container_of(work, struct nfs_local_kiocb, work);
+	struct file *filp = iocb->kiocb.ki_filp;
+	unsigned long old_flags = current->flags;
+	ssize_t status;
+
+	current->flags |= PF_LOCAL_THROTTLE | PF_MEMALLOC_NOIO;
+
+	scoped_with_creds(filp->f_cred)
+		status = do_nfs_local_call_write(iocb, filp);
+
 	current->flags = old_flags;
 }
 
diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c
index 00932500fce4..9e1c48c5c0b8 100644
--- a/fs/nfs/nfs4idmap.c
+++ b/fs/nfs/nfs4idmap.c
@@ -306,15 +306,12 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t namelen,
 				 const char *type, void *data,
 				 size_t data_size, struct idmap *idmap)
 {
-	const struct cred *saved_cred;
 	struct key *rkey;
 	const struct user_key_payload *payload;
 	ssize_t ret;
 
-	saved_cred = override_creds(id_resolver_cache);
-	rkey = nfs_idmap_request_key(name, namelen, type, idmap);
-	revert_creds(saved_cred);
-
+	scoped_with_creds(id_resolver_cache)
+		rkey = nfs_idmap_request_key(name, namelen, type, idmap);
 	if (IS_ERR(rkey)) {
 		ret = PTR_ERR(rkey);
 		goto out;
diff --git a/fs/smb/client/cifs_spnego.c b/fs/smb/client/cifs_spnego.c
index 9891f55bac1e..da935bd1ce87 100644
--- a/fs/smb/client/cifs_spnego.c
+++ b/fs/smb/client/cifs_spnego.c
@@ -90,7 +90,6 @@ cifs_get_spnego_key(struct cifs_ses *sesInfo,
 	size_t desc_len;
 	struct key *spnego_key;
 	const char *hostname = server->hostname;
-	const struct cred *saved_cred;
 
 	/* length of fields (with semicolons): ver=0xyz ip4=ipaddress
 	   host=hostname sec=mechanism uid=0xFF user=username */
@@ -158,9 +157,8 @@ cifs_get_spnego_key(struct cifs_ses *sesInfo,
 		dp += sprintf(dp, ";upcall_target=app");
 
 	cifs_dbg(FYI, "key description = %s\n", description);
-	saved_cred = override_creds(spnego_cred);
-	spnego_key = request_key(&cifs_spnego_key_type, description, "");
-	revert_creds(saved_cred);
+	scoped_with_creds(spnego_cred)
+		spnego_key = request_key(&cifs_spnego_key_type, description, "");
 
 #ifdef CONFIG_CIFS_DEBUG2
 	if (cifsFYI && !IS_ERR(spnego_key)) {