linux-kernel - [PATCH] fs/nfsd: Fix creation time serialization order

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Message-ID: <4154eb6503988c2096f5d30af26d06863fb5d973.1687554467.git.tavianator@tavianator.com>
Date:   Fri, 23 Jun 2023 17:09:06 -0400
From:   tavianator@...ianator.com
To:     linux-nfs@...r.kernel.org
Cc:     Tavian Barnes <tavianator@...ianator.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        Jeff Layton <jlayton@...nel.org>,
        Ondrej Valousek <ondrej.valousek.xm@...esas.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] fs/nfsd: Fix creation time serialization order

From: Tavian Barnes <tavianator@...ianator.com>

In nfsd4_encode_fattr(), TIME_CREATE was being written out after all
other times.  However, they should be written out in an order that
matches the bit flags in bmval1, which in this case are

    #define FATTR4_WORD1_TIME_ACCESS        (1UL << 15)
    #define FATTR4_WORD1_TIME_CREATE        (1UL << 18)
    #define FATTR4_WORD1_TIME_DELTA         (1UL << 19)
    #define FATTR4_WORD1_TIME_METADATA      (1UL << 20)
    #define FATTR4_WORD1_TIME_MODIFY        (1UL << 21)

so TIME_CREATE should come second.

I noticed this on a FreeBSD NFSv4.2 client, which supports creation
times.  On this client, file times were weirdly permuted.  With this
patch applied on the server, times looked normal on the client.

Fixes: e377a3e698fb ("nfsd: Add support for the birth time attribute")
Link: https://unix.stackexchange.com/q/749605/56202
Signed-off-by: Tavian Barnes <tavianator@...ianator.com>
---
 fs/nfsd/nfs4xdr.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 76db2fe29624..3037c5b0623e 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -3354,6 +3354,13 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
 		p = xdr_encode_hyper(p, (s64)stat.atime.tv_sec);
 		*p++ = cpu_to_be32(stat.atime.tv_nsec);
 	}
+	if (bmval1 & FATTR4_WORD1_TIME_CREATE) {
+		p = xdr_reserve_space(xdr, 12);
+		if (!p)
+			goto out_resource;
+		p = xdr_encode_hyper(p, (s64)stat.btime.tv_sec);
+		*p++ = cpu_to_be32(stat.btime.tv_nsec);
+	}
 	if (bmval1 & FATTR4_WORD1_TIME_DELTA) {
 		p = xdr_reserve_space(xdr, 12);
 		if (!p)
@@ -3374,13 +3381,6 @@ nfsd4_encode_fattr(struct xdr_stream *xdr, struct svc_fh *fhp,
 		p = xdr_encode_hyper(p, (s64)stat.mtime.tv_sec);
 		*p++ = cpu_to_be32(stat.mtime.tv_nsec);
 	}
-	if (bmval1 & FATTR4_WORD1_TIME_CREATE) {
-		p = xdr_reserve_space(xdr, 12);
-		if (!p)
-			goto out_resource;
-		p = xdr_encode_hyper(p, (s64)stat.btime.tv_sec);
-		*p++ = cpu_to_be32(stat.btime.tv_nsec);
-	}
 	if (bmval1 & FATTR4_WORD1_MOUNTED_ON_FILEID) {
 		u64 ino = stat.ino;
 
-- 
2.41.0