FAILED: patch "[PATCH] NFSD: return NFS4ERR_EXIST for a guarded OPEN of a" failed to apply to 5.15-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 89318a02fe1c19aac6d85a17c45800544bd3cbe0
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110432-unshackle-deviator-6899@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 89318a02fe1c19aac6d85a17c45800544bd3cbe0 Mon Sep 17 00:00:00 2001
From: Chuck Lever <cel@kernel.org>
Date: Sun, 6 Sep 2026 14:41:41 -0400
Subject: [PATCH] NFSD: return NFS4ERR_EXIST for a guarded OPEN of a
 non-regular object

Commit db8b567ffa98 ("nfsd: (almost) always open file in
nfsd4_create_file()") moved the regular-file type check ahead of the
createmode logic. A GUARDED4, EXCLUSIVE4, or EXCLUSIVE4_1 OPEN that
finds a directory or symbolic link under the requested name now fails
with NFS4ERR_ISDIR or NFS4ERR_SYMLINK instead of NFS4ERR_EXIST.

RFC 8881 Section 18.16.3 requires NFS4ERR_EXIST when a guarded create
finds any object under that name, or when an exclusive create's
verifier does not match. The type-specific errors in Section 18.16.4
apply to opening an existing file, which only UNCHECKED4 does.

Fixes: db8b567ffa98 ("nfsd: (almost) always open file in nfsd4_create_file()")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260906184141.3453309-1-cel@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>

diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index bb74eef43938..3a82af381a8d 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -430,7 +430,17 @@ nfsd4_create_file(struct svc_rqst *rqstp, struct svc_fh *fhp,
 				       oflags,
 				       open->op_iattr.ia_mode);
 	if (IS_ERR(open->op_filp)) {
-		status = nfserrno(PTR_ERR(open->op_filp));
+		int hosterr = PTR_ERR(open->op_filp);
+
+		if (open->op_createmode != NFS4_CREATE_UNCHECKED) {
+			switch (hosterr) {
+			case -EISDIR:
+			case -ELOOP:
+			case -EFTYPE:
+				hosterr = -EEXIST;
+			}
+		}
+		status = nfserrno(hosterr);
 		open->op_filp = NULL;
 		if (status == nfserr_noent && create_status)
 			status = create_status;