FAILED: patch "[PATCH] selftests: mptcp: pm: ensure unknown flags are ignored" failed to apply to 5.15-stable tree

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 <[email protected]>.

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 29f4801e9c8dfd12bdcb33b61a6ac479c7162bd7
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2025122947-enforced-elective-e753@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From 29f4801e9c8dfd12bdcb33b61a6ac479c7162bd7 Mon Sep 17 00:00:00 2001
From: "Matthieu Baerts (NGI0)" <[email protected]>
Date: Fri, 5 Dec 2025 19:55:15 +0100
Subject: [PATCH] selftests: mptcp: pm: ensure unknown flags are ignored

This validates the previous commit: the userspace can set unknown flags -- the 7th bit is currently unused -- without errors, but only the supported ones are printed in the endpoints dumps.

The 'Fixes' tag here below is the same as the one from the previous
commit: this patch here is not fixing anything wrong in the selftests, but it validates the previous fix for an issue introduced by this commit ID.

index ec6a87588191..123d9d7a0278 100755
@@ -192,6 +192,10 @@ check "show_endpoints" \
 flush_endpoint
 check "show_endpoints" "" "flush addrs"
 
+add_endpoint 10.0.1.1 flags unknown
+check "show_endpoints" "$(format_endpoints "1,10.0.1.1")" "ignore unknown flags"
+flush_endpoint
+
 set_limits 9 1 2>/dev/null
 check "get_limits" "${default_limits}" "rcv addrs above hard limit"
 

index 65b374232ff5..99eecccbf0c8 100644
@@ -24,6 +24,8 @@
 #define IPPROTO_MPTCP 262
 #endif
 
+#define MPTCP_PM_ADDR_FLAG_UNKNOWN _BITUL(7)
+
 static void syntax(char *argv[])
 {
 	fprintf(stderr, "%s add|ann|rem|csf|dsf|get|set|del|flush|dump|events|listen|accept [<args>]\n", argv[0]);

@@ -836,6 +838,8 @@ int add_addr(int fd, int pm_family, int argc, char *argv[])
 					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
 				else if (!strcmp(tok, "fullmesh"))
 					flags |= MPTCP_PM_ADDR_FLAG_FULLMESH;
+				else if (!strcmp(tok, "unknown"))
+					flags |= MPTCP_PM_ADDR_FLAG_UNKNOWN;
 				else
 					error(1, errno,
 					      "unknown flag %s", argv[arg]);

@@ -1048,6 +1052,13 @@ static void print_addr(struct rtattr *attrs, int len)
 					printf(",");
 			}
 
+			if (flags & MPTCP_PM_ADDR_FLAG_UNKNOWN) {
+				printf("unknown");
+				flags &= ~MPTCP_PM_ADDR_FLAG_UNKNOWN;
+				if (flags)
+					printf(",");
+			}
+
 			/* bump unknown flags, if any */
 			if (flags)
 				printf("0x%x", flags);

commit 29f4801e9c8dfd12bdcb33b61a6ac479c7162bd7 upstream.

This validates the previous commit: the userspace can set unknown flags -- the 7th bit is currently unused -- without errors, but only the supported ones are printed in the endpoints dumps.

The 'Fixes' tag here below is the same as the one from the previous
commit: this patch here is not fixing anything wrong in the selftests, but it validates the previous fix for an issue introduced by this commit ID.

[ Conflicts in pm_netlink.sh, because some refactoring have been done
later on: commit 0d16ed0c2e74 ("selftests: mptcp: add {get,format}_endpoint(s) helpers") and commit c99d57d0007a ("selftests: mptcp: use pm_nl endpoint ops") are not in this version. The same operation can still be done at the same place, without using the new helpers.
Also, commit 1dc88d241f92 ("selftests: mptcp: pm_nl_ctl: always look for errors") is not in this version, and create a conflict in the context which is not related to the modification here. Conflicts in pm_nl_ctl.c, because commit 69c6ce7b6eca ("selftests:
mptcp: add implicit endpoint test case") is not in this version, and caused a conflict in the context which is not related to the modification here. ]

---
 tools/testing/selftests/net/mptcp/pm_netlink.sh |  4 ++++
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c   | 11 +++++++++++
 2 files changed, 15 insertions(+)

index 68e05bd3526e..e3ab2f5ef304 100755
@@ -124,6 +124,10 @@ id 8 flags signal 10.0.1.8" "id limit"
 ip netns exec $ns1 ./pm_nl_ctl flush
 check "ip netns exec $ns1 ./pm_nl_ctl dump" "" "flush addrs"
 
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1 flags unknown
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.1.1" "ignore unknown flags"
+ip netns exec $ns1 ./pm_nl_ctl flush
+
 ip netns exec $ns1 ./pm_nl_ctl limits 9 1
 check "ip netns exec $ns1 ./pm_nl_ctl limits" "$default_limits" "rcv addrs above hard limit"
 

index 354784512748..e50075be0e4d 100644
@@ -22,6 +22,8 @@
 #define MPTCP_PM_NAME		"mptcp_pm"
 #endif
 
+#define MPTCP_PM_ADDR_FLAG_UNKNOWN _BITUL(7)
+
 static void syntax(char *argv[])
 {
 	fprintf(stderr, "%s add|get|set|del|flush|dump|accept [<args>]\n", argv[0]);

@@ -238,6 +240,8 @@ int add_addr(int fd, int pm_family, int argc, char *argv[])
 					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
 				else if (!strcmp(tok, "fullmesh"))
 					flags |= MPTCP_PM_ADDR_FLAG_FULLMESH;
+				else if (!strcmp(tok, "unknown"))
+					flags |= MPTCP_PM_ADDR_FLAG_UNKNOWN;
 				else
 					error(1, errno,
 					      "unknown flag %s", argv[arg]);

@@ -436,6 +440,13 @@ static void print_addr(struct rtattr *attrs, int len)
 					printf(",");
 			}
 
+			if (flags & MPTCP_PM_ADDR_FLAG_UNKNOWN) {
+				printf("unknown");
+				flags &= ~MPTCP_PM_ADDR_FLAG_UNKNOWN;
+				if (flags)
+					printf(",");
+			}
+
 			/* bump unknown flags, if any */
 			if (flags)
 				printf("0x%x", flags);

2.51.0

This is a note to let you know that I've just added the patch titled

selftests: mptcp: pm: ensure unknown flags are ignored

to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
selftests-mptcp-pm-ensure-unknown-flags-are-ignored.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From [email protected] Thu Feb 12 12:04:04 2026
From: "Matthieu Baerts (NGI0)" <[email protected]>
Date: Thu, 12 Feb 2026 12:03:45 +0100
Subject: selftests: mptcp: pm: ensure unknown flags are ignored
To: [email protected], [email protected]
Cc: MPTCP Upstream <[email protected]>, "Matthieu Baerts (NGI0)" <[email protected]>, Mat Martineau <[email protected]>, Jakub Kicinski <[email protected]>
Message-ID: <[email protected]>

From: "Matthieu Baerts (NGI0)" <[email protected]>

commit 29f4801e9c8dfd12bdcb33b61a6ac479c7162bd7 upstream.

This validates the previous commit: the userspace can set unknown flags -- the 7th bit is currently unused -- without errors, but only the supported ones are printed in the endpoints dumps.

The 'Fixes' tag here below is the same as the one from the previous
commit: this patch here is not fixing anything wrong in the selftests, but it validates the previous fix for an issue introduced by this commit ID.

[ Conflicts in pm_netlink.sh, because some refactoring have been done
later on: commit 0d16ed0c2e74 ("selftests: mptcp: add {get,format}_endpoint(s) helpers") and commit c99d57d0007a ("selftests: mptcp: use pm_nl endpoint ops") are not in this version. The same operation can still be done at the same place, without using the new helpers.
Also, commit 1dc88d241f92 ("selftests: mptcp: pm_nl_ctl: always look for errors") is not in this version, and create a conflict in the context which is not related to the modification here. Conflicts in pm_nl_ctl.c, because commit 69c6ce7b6eca ("selftests:
mptcp: add implicit endpoint test case") is not in this version, and caused a conflict in the context which is not related to the modification here. ]

---
 tools/testing/selftests/net/mptcp/pm_netlink.sh |    4 ++++
 tools/testing/selftests/net/mptcp/pm_nl_ctl.c   |   11 +++++++++++
 2 files changed, 15 insertions(+)

@@ -124,6 +124,10 @@ id 8 flags signal 10.0.1.8" "id limit"
 ip netns exec $ns1 ./pm_nl_ctl flush
 check "ip netns exec $ns1 ./pm_nl_ctl dump" "" "flush addrs"
 
+ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.1 flags unknown
+check "ip netns exec $ns1 ./pm_nl_ctl dump" "id 1 flags  10.0.1.1" "ignore unknown flags"
+ip netns exec $ns1 ./pm_nl_ctl flush
+
 ip netns exec $ns1 ./pm_nl_ctl limits 9 1
 check "ip netns exec $ns1 ./pm_nl_ctl limits" "$default_limits" "rcv addrs above hard limit"
 

@@ -22,6 +22,8 @@
 #define MPTCP_PM_NAME		"mptcp_pm"
 #endif
 
+#define MPTCP_PM_ADDR_FLAG_UNKNOWN _BITUL(7)
+
 static void syntax(char *argv[])
 {
 	fprintf(stderr, "%s add|get|set|del|flush|dump|accept [<args>]\n", argv[0]);

@@ -238,6 +240,8 @@ int add_addr(int fd, int pm_family, int
 					flags |= MPTCP_PM_ADDR_FLAG_BACKUP;
 				else if (!strcmp(tok, "fullmesh"))
 					flags |= MPTCP_PM_ADDR_FLAG_FULLMESH;
+				else if (!strcmp(tok, "unknown"))
+					flags |= MPTCP_PM_ADDR_FLAG_UNKNOWN;
 				else
 					error(1, errno,
 					      "unknown flag %s", argv[arg]);

@@ -435,6 +439,13 @@ static void print_addr(struct rtattr *at
 				if (flags)
 					printf(",");
 			}
+
+			if (flags & MPTCP_PM_ADDR_FLAG_UNKNOWN) {
+				printf("unknown");
+				flags &= ~MPTCP_PM_ADDR_FLAG_UNKNOWN;
+				if (flags)
+					printf(",");
+			}
 
 			/* bump unknown flags, if any */
 			if (flags)

Patches currently in stable-queue which might be from [email protected] are

queue-5.15/mptcp-fix-race-in-mptcp_pm_nl_flush_addrs_doit.patch queue-5.15/selftests-mptcp-pm-ensure-unknown-flags-are-ignored.patch