From: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Date: Thu, 15 Jan 2026 03:15:36 +0000 (+0000)
Subject: alloc_tag: fix rw permission issue when handling boot parameter
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=77bcee8d4015a1191e1e3f5c5c51589086493ab0;p=thirdparty%2Fkernel%2Flinux.git

alloc_tag: fix rw permission issue when handling boot parameter

Boot parameters prefixed with "sysctl." are processed during the final
stage of system initialization via kernel_init()-> do_sysctl_args().  When
CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled, the sysctl.vm.mem_profiling
entry is not writable and will cause a warning.

Before run_init_process(), system initialization executes in kernel thread
context.  Use current->mm to distinguish sysctl writes during
do_sysctl_args() from user-space triggered ones.

And when the proc_handler is from do_sysctl_args(), always return success
because the same value was already set by setup_early_mem_profiling() and
this eliminates a permission denied warning.

Link: https://lkml.kernel.org/r/20260115031536.164254-1-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Suggested-by: Suren Baghdasaryan <surenb@google.com>
Acked-by: Suren Baghdasaryan <surenb@google.com>
Cc: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c
index 846a5b5b44a4e..00ae4673a2717 100644
--- a/lib/alloc_tag.c
+++ b/lib/alloc_tag.c
@@ -776,8 +776,22 @@ EXPORT_SYMBOL(page_alloc_tagging_ops);
 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;
+	if (write) {
+		/*
+		 * Call from do_sysctl_args() which is a no-op since the same
+		 * value was already set by setup_early_mem_profiling.
+		 * Return success to avoid warnings from do_sysctl_args().
+		 */
+		if (!current->mm)
+			return 0;
+
+#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
+		/* User can't toggle profiling while debugging */
+		return -EACCES;
+#endif
+		if (!mem_profiling_support)
+			return -EINVAL;
+	}
 
 	return proc_do_static_key(table, write, buffer, lenp, ppos);
 }
@@ -787,11 +801,7 @@ static const struct ctl_table memory_allocation_profiling_sysctls[] = {
 	{
 		.procname	= "mem_profiling",
 		.data		= &mem_alloc_profiling_key,
-#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG
-		.mode		= 0444,
-#else
 		.mode		= 0644,
-#endif
 		.proc_handler	= proc_mem_profiling_handler,
 	},
 };