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FAILED: patch "[PATCH] nsfs: tighten permission checks for ns iteration ioctls" failed to apply to 6.18-stable tree

PATCH New [email protected] 2 participants 2 messages Mar 17

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author maintainer
#0 lore raw

The patch below does not apply to the 6.18-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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x e6b899f08066e744f89df16ceb782e06868bd148
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026031747-sweat-levitate-59b2@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

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

From e6b899f08066e744f89df16ceb782e06868bd148 Mon Sep 17 00:00:00 2001
From: Christian Brauner <[email protected]>
Date: Thu, 26 Feb 2026 14:50:09 +0100
Subject: [PATCH] nsfs: tighten permission checks for ns iteration ioctls

Even privileged services should not necessarily be able to see other privileged service's namespaces so they can't leak information to each other. Use may_see_all_namespaces() helper that centralizes this policy until the nstree adapts.

Link https://patch.msgid.link/[email protected] open here
Fixes a1d220d9dafa ("nsfs: iterate through mount namespaces")
Reviewed-by Jeff Layton <[email protected]>
Cc [email protected] # v6.12+
Signed-off-by Christian Brauner <[email protected]>
fs/nsfs.c +13 -0
index db91de208645..be36c10c38cf 100644
@@ -199,6 +199,17 @@ static bool nsfs_ioctl_valid(unsigned int cmd)
 	return false;
 }
 
+static bool may_use_nsfs_ioctl(unsigned int cmd)
+{
+	switch (_IOC_NR(cmd)) {
+	case _IOC_NR(NS_MNT_GET_NEXT):
+		fallthrough;
+	case _IOC_NR(NS_MNT_GET_PREV):
+		return may_see_all_namespaces();
+	}
+	return true;
+}
+
 static long ns_ioctl(struct file *filp, unsigned int ioctl,
 			unsigned long arg)
 {

@@ -214,6 +225,8 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 
 	if (!nsfs_ioctl_valid(ioctl))
 		return -ENOIOCTLCMD;
+	if (!may_use_nsfs_ioctl(ioctl))
+		return -EPERM;
 
 	ns = get_proc_ns(file_inode(filp));
 	switch (ioctl) {
include/linux/ns_common.h +2 -0
index 825f5865bfc5..c8e227a3f9e2 100644
@@ -55,6 +55,8 @@ static __always_inline bool is_ns_init_id(const struct ns_common *ns)
 
 #define ns_common_free(__ns) __ns_common_free(to_ns_common((__ns)))
 
+bool may_see_all_namespaces(void);
+
 static __always_inline __must_check int __ns_ref_active_read(const struct ns_common *ns)
 {
 	return atomic_read(&ns->__ns_ref_active);
kernel/nscommon.c +6 -0
index bdc3c86231d3..3166c1fd844a 100644
@@ -309,3 +309,9 @@ void __ns_ref_active_get(struct ns_common *ns)
 			return;
 	}
 }
+
+bool may_see_all_namespaces(void)
+{
+	return (task_active_pid_ns(current) == &init_pid_ns) &&
+	       ns_capable_noaudit(init_pid_ns.user_ns, CAP_SYS_ADMIN);
+}
maintainer
#1 lore raw

PATCH 1/1 nsfs: tighten permission checks for ns iteration ioctls

From: Christian Brauner <[email protected]>

[ Upstream commit e6b899f08066e744f89df16ceb782e06868bd148 ]

Even privileged services should not necessarily be able to see other privileged service's namespaces so they can't leak information to each other. Use may_see_all_namespaces() helper that centralizes this policy until the nstree adapts.

Link https://patch.msgid.link/[email protected] open here
Fixes a1d220d9dafa ("nsfs: iterate through mount namespaces")
Reviewed-by Jeff Layton <[email protected]>
Cc [email protected] # v6.12+
Signed-off-by Christian Brauner <[email protected]>
[ context ]
Signed-off-by Sasha Levin <[email protected]>
---
 fs/nsfs.c                 | 13 +++++++++++++
 include/linux/ns_common.h |  2 ++
 kernel/nscommon.c         |  6 ++++++
 3 files changed, 21 insertions(+)
fs/nsfs.c +13 -0
index 79b026a36fb62..f22c2a636e8f3 100644
@@ -194,6 +194,17 @@ static bool nsfs_ioctl_valid(unsigned int cmd)
 	return false;
 }
 
+static bool may_use_nsfs_ioctl(unsigned int cmd)
+{
+	switch (_IOC_NR(cmd)) {
+	case _IOC_NR(NS_MNT_GET_NEXT):
+		fallthrough;
+	case _IOC_NR(NS_MNT_GET_PREV):
+		return may_see_all_namespaces();
+	}
+	return true;
+}
+
 static long ns_ioctl(struct file *filp, unsigned int ioctl,
 			unsigned long arg)
 {

@@ -209,6 +220,8 @@ static long ns_ioctl(struct file *filp, unsigned int ioctl,
 
 	if (!nsfs_ioctl_valid(ioctl))
 		return -ENOIOCTLCMD;
+	if (!may_use_nsfs_ioctl(ioctl))
+		return -EPERM;
 
 	ns = get_proc_ns(file_inode(filp));
 	switch (ioctl) {
include/linux/ns_common.h +2 -0
index 71a5e28344d11..f3c52904343e7 100644
@@ -144,6 +144,8 @@ void __ns_common_free(struct ns_common *ns);
 
 #define ns_common_free(__ns) __ns_common_free(to_ns_common((__ns)))
 
+bool may_see_all_namespaces(void);
+
 static __always_inline __must_check bool __ns_ref_put(struct ns_common *ns)
 {
 	return refcount_dec_and_test(&ns->__ns_ref);
kernel/nscommon.c +6 -0
index c1fb2bad6d729..22b5c5d0385f5 100644
@@ -75,3 +75,9 @@ void __ns_common_free(struct ns_common *ns)
 {
 	proc_free_inum(ns->inum);
 }
+
+bool may_see_all_namespaces(void)
+{
+	return (task_active_pid_ns(current) == &init_pid_ns) &&
+	       ns_capable_noaudit(init_pid_ns.user_ns, CAP_SYS_ADMIN);
+}
Signature · 1 line
2.51.0