FAILED: patch "[PATCH] proc: protect ptrace_may_access() with exec_update_lock (part" failed to apply to 6.18-stable tree

FAILED: patch "[PATCH] proc: protect ptrace_may_access() with exec_update_lock (part" failed to apply to 6.18-stable tree

[gregkh]

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 <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-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 6650527444dadc63d84aa939d14ecba4fadb2f69
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026071444-fraction-t-shirt-9b49@gregkh' --subject-prefix 'PATCH 6.18.y' 'HEAD^..'

Possible dependencies:



thanks,

greg k-h

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

From 6650527444dadc63d84aa939d14ecba4fadb2f69 Mon Sep 17 00:00:00 2001
From: Jann Horn <jannh@google.com>
Date: Mon, 18 May 2026 18:35:15 +0200
Subject: [PATCH] proc: protect ptrace_may_access() with exec_update_lock (part
 1)

Fix the easy cases where procfs currently calls ptrace_may_access() without
exec_update_lock protection, where the fix is to simply add the extra lock
or use mm_access():

 - do_task_stat(): grab exec_update_lock
 - proc_pid_wchan(): grab exec_update_lock
 - proc_map_files_lookup(): use mm_access() instead of get_task_mm()
 - proc_map_files_readdir(): use mm_access() instead of get_task_mm()
 - proc_ns_get_link(): grab exec_update_lock
 - proc_ns_readlink(): grab exec_update_lock

Fixes: f83ce3e6b02d ("proc: avoid information leaks to non-privileged processes")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://patch.msgid.link/20260518-procfs-lockfix-part1-v1-1-5c3d20e0ac33@google.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 90fb0c6b5f99..479ea8cb4ef4 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -482,6 +482,11 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	unsigned long flags;
 	int exit_code = task->exit_code;
 	struct signal_struct *sig = task->signal;
+	int ret;
+
+	ret = down_read_killable(&task->signal->exec_update_lock);
+	if (ret)
+		return ret;
 
 	state = *get_task_state(task);
 	vsize = eip = esp = 0;
@@ -657,6 +662,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 		seq_puts(m, " 0");
 
 	seq_putc(m, '\n');
+	up_read(&task->signal->exec_update_lock);
 	if (mm)
 		mmput(mm);
 	return 0;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d9acfa89c894..cc99d953a0a3 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -423,18 +423,24 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
 {
 	unsigned long wchan;
 	char symname[KSYM_NAME_LEN];
+	int err;
 
+	err = down_read_killable(&task->signal->exec_update_lock);
+	if (err)
+		return err;
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
 		goto print0;
 
 	wchan = get_wchan(task);
 	if (wchan && !lookup_symbol_name(wchan, symname)) {
 		seq_puts(m, symname);
+		up_read(&task->signal->exec_update_lock);
 		return 0;
 	}
 
 print0:
 	seq_putc(m, '0');
+	up_read(&task->signal->exec_update_lock);
 	return 0;
 }
 #endif /* CONFIG_KALLSYMS */
@@ -2360,17 +2366,15 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
 	if (!task)
 		goto out;
 
-	result = ERR_PTR(-EACCES);
-	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
-		goto out_put_task;
-
 	result = ERR_PTR(-ENOENT);
 	if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
 		goto out_put_task;
 
-	mm = get_task_mm(task);
-	if (!mm)
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR(mm)) {
+		result = ERR_CAST(mm);
 		goto out_put_task;
+	}
 
 	result = ERR_PTR(-EINTR);
 	if (mmap_read_lock_killable(mm))
@@ -2420,24 +2424,23 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 	if (!task)
 		goto out;
 
-	ret = -EACCES;
-	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
-		goto out_put_task;
-
 	ret = 0;
 	if (!dir_emit_dots(file, ctx))
 		goto out_put_task;
 
-	mm = get_task_mm(task);
-	if (!mm)
-		goto out_put_task;
-
-	ret = mmap_read_lock_killable(mm);
-	if (ret) {
-		mmput(mm);
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR(mm)) {
+		ret = PTR_ERR(mm);
+		/* if the task has no mm, the directory should just be empty */
+		if (ret == -ESRCH)
+			ret = 0;
 		goto out_put_task;
 	}
 
+	ret = mmap_read_lock_killable(mm);
+	if (ret)
+		goto out_put_mm;
+
 	nr_files = 0;
 
 	/*
@@ -2462,8 +2465,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		if (!p) {
 			ret = -ENOMEM;
 			mmap_read_unlock(mm);
-			mmput(mm);
-			goto out_put_task;
+			goto out_put_mm;
 		}
 
 		p->start = vma->vm_start;
@@ -2471,7 +2473,6 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		p->mode = vma->vm_file->f_mode;
 	}
 	mmap_read_unlock(mm);
-	mmput(mm);
 
 	for (i = 0; i < nr_files; i++) {
 		char buf[4 * sizeof(long) + 2];	/* max: %lx-%lx\0 */
@@ -2488,6 +2489,8 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		ctx->pos++;
 	}
 
+out_put_mm:
+	mmput(mm);
 out_put_task:
 	put_task_struct(task);
 out:
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index 39f4169f669f..2f46f1396744 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -55,6 +55,10 @@ static const char *proc_ns_get_link(struct dentry *dentry,
 	if (!task)
 		return ERR_PTR(-EACCES);
 
+	error = down_read_killable(&task->signal->exec_update_lock);
+	if (error)
+		goto out_put_task;
+
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
 		goto out;
 
@@ -64,6 +68,8 @@ static const char *proc_ns_get_link(struct dentry *dentry,
 
 	error = nd_jump_link(&ns_path);
 out:
+	up_read(&task->signal->exec_update_lock);
+out_put_task:
 	put_task_struct(task);
 	return ERR_PTR(error);
 }
@@ -80,11 +86,17 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
 	if (!task)
 		return res;
 
+	res = down_read_killable(&task->signal->exec_update_lock);
+	if (res)
+		goto out_put_task;
+
 	if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
 		res = ns_get_name(name, sizeof(name), task, ns_ops);
 		if (res >= 0)
 			res = readlink_copy(buffer, buflen, name, strlen(name));
 	}
+	up_read(&task->signal->exec_update_lock);
+out_put_task:
 	put_task_struct(task);
 	return res;
 }

[PATCH 6.18.y 1/3] seqlock: Introduce scoped_seqlock_read()

[Sasha Levin]

From: Peter Zijlstra <peterz@infradead.org>

[ Upstream commit cc39f3872c0865bef992b713338df369554fa9e0 ]

The read_seqbegin/need_seqretry/done_seqretry API is cumbersome and
error prone. With the new helper the "typical" code like

	int seq, nextseq;
	unsigned long flags;

	nextseq = 0;
	do {
		seq = nextseq;
		flags = read_seqbegin_or_lock_irqsave(&seqlock, &seq);

		// read-side critical section

		nextseq = 1;
	} while (need_seqretry(&seqlock, seq));
	done_seqretry_irqrestore(&seqlock, seq, flags);

can be rewritten as

	scoped_seqlock_read (&seqlock, ss_lock_irqsave) {
		// read-side critical section
	}

Original idea by Oleg Nesterov; with contributions from Linus.

Originally-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Stable-dep-of: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/linux/seqlock.h | 111 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 111 insertions(+)

diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
index 5ce48eab7a2ad7..b7bcc4111e908c 100644
--- a/include/linux/seqlock.h
+++ b/include/linux/seqlock.h
@@ -1209,4 +1209,115 @@ done_seqretry_irqrestore(seqlock_t *lock, int seq, unsigned long flags)
 	if (seq & 1)
 		read_sequnlock_excl_irqrestore(lock, flags);
 }
+
+enum ss_state {
+	ss_done = 0,
+	ss_lock,
+	ss_lock_irqsave,
+	ss_lockless,
+};
+
+struct ss_tmp {
+	enum ss_state	state;
+	unsigned long	data;
+	spinlock_t	*lock;
+	spinlock_t	*lock_irqsave;
+};
+
+static inline void __scoped_seqlock_cleanup(struct ss_tmp *sst)
+{
+	if (sst->lock)
+		spin_unlock(sst->lock);
+	if (sst->lock_irqsave)
+		spin_unlock_irqrestore(sst->lock_irqsave, sst->data);
+}
+
+extern void __scoped_seqlock_invalid_target(void);
+
+#if defined(CONFIG_CC_IS_GCC) && CONFIG_GCC_VERSION < 90000
+/*
+ * For some reason some GCC-8 architectures (nios2, alpha) have trouble
+ * determining that the ss_done state is impossible in __scoped_seqlock_next()
+ * below.
+ */
+static inline void __scoped_seqlock_bug(void) { }
+#else
+/*
+ * Canary for compiler optimization -- if the compiler doesn't realize this is
+ * an impossible state, it very likely generates sub-optimal code here.
+ */
+extern void __scoped_seqlock_bug(void);
+#endif
+
+static inline void
+__scoped_seqlock_next(struct ss_tmp *sst, seqlock_t *lock, enum ss_state target)
+{
+	switch (sst->state) {
+	case ss_done:
+		__scoped_seqlock_bug();
+		return;
+
+	case ss_lock:
+	case ss_lock_irqsave:
+		sst->state = ss_done;
+		return;
+
+	case ss_lockless:
+		if (!read_seqretry(lock, sst->data)) {
+			sst->state = ss_done;
+			return;
+		}
+		break;
+	}
+
+	switch (target) {
+	case ss_done:
+		__scoped_seqlock_invalid_target();
+		return;
+
+	case ss_lock:
+		sst->lock = &lock->lock;
+		spin_lock(sst->lock);
+		sst->state = ss_lock;
+		return;
+
+	case ss_lock_irqsave:
+		sst->lock_irqsave = &lock->lock;
+		spin_lock_irqsave(sst->lock_irqsave, sst->data);
+		sst->state = ss_lock_irqsave;
+		return;
+
+	case ss_lockless:
+		sst->data = read_seqbegin(lock);
+		return;
+	}
+}
+
+#define __scoped_seqlock_read(_seqlock, _target, _s)			\
+	for (struct ss_tmp _s __cleanup(__scoped_seqlock_cleanup) =	\
+	     { .state = ss_lockless, .data = read_seqbegin(_seqlock) };	\
+	     _s.state != ss_done;					\
+	     __scoped_seqlock_next(&_s, _seqlock, _target))
+
+/**
+ * scoped_seqlock_read (lock, ss_state) - execute the read side critical
+ *                                        section without manual sequence
+ *                                        counter handling or calls to other
+ *                                        helpers
+ * @lock: pointer to seqlock_t protecting the data
+ * @ss_state: one of {ss_lock, ss_lock_irqsave, ss_lockless} indicating
+ *            the type of critical read section
+ *
+ * Example:
+ *
+ *     scoped_seqlock_read (&lock, ss_lock) {
+ *         // read-side critical section
+ *     }
+ *
+ * Starts with a lockess pass first. If it fails, restarts the critical
+ * section with the lock held.
+ */
+#define scoped_seqlock_read(_seqlock, _target)				\
+	__scoped_seqlock_read(_seqlock, _target, __UNIQUE_ID(seqlock))
+
 #endif /* __LINUX_SEQLOCK_H */
-- 
2.53.0

[PATCH 6.18.y 2/3] seqlock: Change do_task_stat() to use scoped_seqlock_read()

[Sasha Levin]

From: Oleg Nesterov <oleg@redhat.com>

[ Upstream commit b76f72bea2c601afec81829ea427fc0d20f83216 ]

To simplify the code and make it more readable.

[peterz: change to new interface]
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Stable-dep-of: 6650527444da ("proc: protect ptrace_may_access() with exec_update_lock (part 1)")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/proc/array.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 038d4b57127fef..4602a38f85d829 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -481,7 +481,6 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	unsigned long flags;
 	int exit_code = task->exit_code;
 	struct signal_struct *sig = task->signal;
-	unsigned int seq = 1;
 
 	state = *get_task_state(task);
 	vsize = eip = esp = 0;
@@ -538,10 +537,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	if (permitted && (!whole || num_threads < 2))
 		wchan = !task_is_running(task);
 
-	do {
-		seq++; /* 2 on the 1st/lockless path, otherwise odd */
-		flags = read_seqbegin_or_lock_irqsave(&sig->stats_lock, &seq);
-
+	scoped_seqlock_read (&sig->stats_lock, ss_lock_irqsave) {
 		cmin_flt = sig->cmin_flt;
 		cmaj_flt = sig->cmaj_flt;
 		cutime = sig->cutime;
@@ -563,8 +559,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 			}
 			rcu_read_unlock();
 		}
-	} while (need_seqretry(&sig->stats_lock, seq));
-	done_seqretry_irqrestore(&sig->stats_lock, seq, flags);
+	}
 
 	if (whole) {
 		thread_group_cputime_adjusted(task, &utime, &stime);
-- 
2.53.0

[PATCH 6.18.y 3/3] proc: protect ptrace_may_access() with exec_update_lock (part 1)

[Sasha Levin]

From: Jann Horn <jannh@google.com>

[ Upstream commit 6650527444dadc63d84aa939d14ecba4fadb2f69 ]

Fix the easy cases where procfs currently calls ptrace_may_access() without
exec_update_lock protection, where the fix is to simply add the extra lock
or use mm_access():

 - do_task_stat(): grab exec_update_lock
 - proc_pid_wchan(): grab exec_update_lock
 - proc_map_files_lookup(): use mm_access() instead of get_task_mm()
 - proc_map_files_readdir(): use mm_access() instead of get_task_mm()
 - proc_ns_get_link(): grab exec_update_lock
 - proc_ns_readlink(): grab exec_update_lock

Fixes: f83ce3e6b02d ("proc: avoid information leaks to non-privileged processes")
Cc: stable@vger.kernel.org
Signed-off-by: Jann Horn <jannh@google.com>
Link: https://patch.msgid.link/20260518-procfs-lockfix-part1-v1-1-5c3d20e0ac33@google.com
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 fs/proc/array.c      |  6 ++++++
 fs/proc/base.c       | 41 ++++++++++++++++++++++-------------------
 fs/proc/namespaces.c | 12 ++++++++++++
 3 files changed, 40 insertions(+), 19 deletions(-)

diff --git a/fs/proc/array.c b/fs/proc/array.c
index 4602a38f85d829..38f96af7b521be 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -481,6 +481,11 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 	unsigned long flags;
 	int exit_code = task->exit_code;
 	struct signal_struct *sig = task->signal;
+	int ret;
+
+	ret = down_read_killable(&task->signal->exec_update_lock);
+	if (ret)
+		return ret;
 
 	state = *get_task_state(task);
 	vsize = eip = esp = 0;
@@ -656,6 +661,7 @@ static int do_task_stat(struct seq_file *m, struct pid_namespace *ns,
 		seq_puts(m, " 0");
 
 	seq_putc(m, '\n');
+	up_read(&task->signal->exec_update_lock);
 	if (mm)
 		mmput(mm);
 	return 0;
diff --git a/fs/proc/base.c b/fs/proc/base.c
index a314fd9af17c08..80df75e13fa338 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -423,18 +423,24 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
 {
 	unsigned long wchan;
 	char symname[KSYM_NAME_LEN];
+	int err;
 
+	err = down_read_killable(&task->signal->exec_update_lock);
+	if (err)
+		return err;
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
 		goto print0;
 
 	wchan = get_wchan(task);
 	if (wchan && !lookup_symbol_name(wchan, symname)) {
 		seq_puts(m, symname);
+		up_read(&task->signal->exec_update_lock);
 		return 0;
 	}
 
 print0:
 	seq_putc(m, '0');
+	up_read(&task->signal->exec_update_lock);
 	return 0;
 }
 #endif /* CONFIG_KALLSYMS */
@@ -2360,17 +2366,15 @@ static struct dentry *proc_map_files_lookup(struct inode *dir,
 	if (!task)
 		goto out;
 
-	result = ERR_PTR(-EACCES);
-	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
-		goto out_put_task;
-
 	result = ERR_PTR(-ENOENT);
 	if (dname_to_vma_addr(dentry, &vm_start, &vm_end))
 		goto out_put_task;
 
-	mm = get_task_mm(task);
-	if (!mm)
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR(mm)) {
+		result = ERR_CAST(mm);
 		goto out_put_task;
+	}
 
 	result = ERR_PTR(-EINTR);
 	if (mmap_read_lock_killable(mm))
@@ -2420,23 +2424,22 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 	if (!task)
 		goto out;
 
-	ret = -EACCES;
-	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
-		goto out_put_task;
-
 	ret = 0;
 	if (!dir_emit_dots(file, ctx))
 		goto out_put_task;
 
-	mm = get_task_mm(task);
-	if (!mm)
+	mm = mm_access(task, PTRACE_MODE_READ_FSCREDS);
+	if (IS_ERR(mm)) {
+		ret = PTR_ERR(mm);
+		/* if the task has no mm, the directory should just be empty */
+		if (ret == -ESRCH)
+			ret = 0;
 		goto out_put_task;
+	}
 
 	ret = mmap_read_lock_killable(mm);
-	if (ret) {
-		mmput(mm);
-		goto out_put_task;
-	}
+	if (ret)
+		goto out_put_mm;
 
 	nr_files = 0;
 
@@ -2462,8 +2465,7 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		if (!p) {
 			ret = -ENOMEM;
 			mmap_read_unlock(mm);
-			mmput(mm);
-			goto out_put_task;
+			goto out_put_mm;
 		}
 
 		p->start = vma->vm_start;
@@ -2471,7 +2473,6 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		p->mode = vma->vm_file->f_mode;
 	}
 	mmap_read_unlock(mm);
-	mmput(mm);
 
 	for (i = 0; i < nr_files; i++) {
 		char buf[4 * sizeof(long) + 2];	/* max: %lx-%lx\0 */
@@ -2488,6 +2489,8 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx)
 		ctx->pos++;
 	}
 
+out_put_mm:
+	mmput(mm);
 out_put_task:
 	put_task_struct(task);
 out:
diff --git a/fs/proc/namespaces.c b/fs/proc/namespaces.c
index ea2b597fd92cdb..f99b7f3fa57445 100644
--- a/fs/proc/namespaces.c
+++ b/fs/proc/namespaces.c
@@ -55,6 +55,10 @@ static const char *proc_ns_get_link(struct dentry *dentry,
 	if (!task)
 		return ERR_PTR(-EACCES);
 
+	error = down_read_killable(&task->signal->exec_update_lock);
+	if (error)
+		goto out_put_task;
+
 	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
 		goto out;
 
@@ -64,6 +68,8 @@ static const char *proc_ns_get_link(struct dentry *dentry,
 
 	error = nd_jump_link(&ns_path);
 out:
+	up_read(&task->signal->exec_update_lock);
+out_put_task:
 	put_task_struct(task);
 	return ERR_PTR(error);
 }
@@ -80,11 +86,17 @@ static int proc_ns_readlink(struct dentry *dentry, char __user *buffer, int bufl
 	if (!task)
 		return res;
 
+	res = down_read_killable(&task->signal->exec_update_lock);
+	if (res)
+		goto out_put_task;
+
 	if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) {
 		res = ns_get_name(name, sizeof(name), task, ns_ops);
 		if (res >= 0)
 			res = readlink_copy(buffer, buflen, name, strlen(name));
 	}
+	up_read(&task->signal->exec_update_lock);
+out_put_task:
 	put_task_struct(task);
 	return res;
 }
-- 
2.53.0