linux-kernel - [PATCH v2 2/3] alloc_tag: prevent enabling memory profiling if it was shut down

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Message-ID: <20250915212756.3998938-3-surenb@google.com>
Date: Mon, 15 Sep 2025 14:27:55 -0700
From: Suren Baghdasaryan <surenb@...gle.com>
To: akpm@...ux-foundation.org
Cc: kent.overstreet@...ux.dev, vbabka@...e.cz, hannes@...xchg.org, 
	usamaarif642@...il.com, shakeel.butt@...ux.dev, 00107082@....com, 
	pasha.tatashin@...een.com, souravpanda@...gle.com, surenb@...gle.com, 
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] alloc_tag: prevent enabling memory profiling if it was
 shut down

Memory profiling can be shut down due to reasons like a failure during
initialization. When this happens, the user should not be able to
re-enable it. Current sysctrl interface does not handle this properly
and will allow re-enabling memory profiling. Fix this by checking for
this condition during sysctrl write operation.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>
Acked-by: Shakeel Butt <shakeel.butt@...ux.dev>
Acked-by: Usama Arif <usamaarif642@...il.com>
---
 lib/alloc_tag.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 715315f5d9ba..f79217427d81 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -766,6 +766,20 @@ struct page_ext_operations page_alloc_tagging_ops = {
 EXPORT_SYMBOL(page_alloc_tagging_ops);
 
 #ifdef CONFIG_SYSCTL
+/*
+ * Not using proc_do_static_key() directly to prevent enabling profiling
+ * after it was shut down.
+ */
+static int proc_mem_profiling_handler(const struct ctl_table *table, int write,
+				      void *buffer, size_t *lenp, loff_t *ppos)
+{
+	if (!mem_profiling_support && write)
+		return -EINVAL;
+
+	return proc_do_static_key(table, write, buffer, lenp, ppos);
+}
+
+
 static struct ctl_table memory_allocation_profiling_sysctls[] = {
 	{
 		.procname	= "mem_profiling",
@@ -775,7 +789,7 @@ static struct ctl_table memory_allocation_profiling_sysctls[] = {
 #else
 		.mode		= 0644,
 #endif
-		.proc_handler	= proc_do_static_key,
+		.proc_handler	= proc_mem_profiling_handler,
 	},
 };
 
-- 
2.51.0.384.g4c02a37b29-goog