linux-kernel - Re: [PATCH v2] alloc_tag: fix rw permission issue when handling boot parameter

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Message-Id: <20260114192336.9d98f0330bfd6c8638762dd0@linux-foundation.org>
Date: Wed, 14 Jan 2026 19:23:36 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: ranxiaokai627@....com
Cc: surenb@...gle.com, kent.overstreet@...ux.dev, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, ran.xiaokai@....com.cn
Subject: Re: [PATCH v2] alloc_tag: fix rw permission issue when handling
 boot parameter

On Thu, 15 Jan 2026 03:15:36 +0000 ranxiaokai627@....com wrote:

> From: Ran Xiaokai <ran.xiaokai@....com.cn>
> 
> 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.

This sounds strange.  Why would setting a Kconfig debug thing disable
alteration of a runtime control? 
Documentation/mm/allocation-profiling.rst provided no hint.

> 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.
> 
> Suggested-by: Suren Baghdasaryan <surenb@...gle.com>
> Acked-by: Suren Baghdasaryan <surenb@...gle.com>
> Signed-off-by: Ran Xiaokai <ran.xiaokai@....com.cn>

Should we backport it?