linux-kernel - Re: [PATCH] proc: proc_maps_open allow proc_mem

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Message-Id: <20250807154606.131d96b133c19baca0c5f2e6@linux-foundation.org>
Date: Thu, 7 Aug 2025 15:46:06 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Jialin Wang <wjl.linux@...il.com>
Cc: Penglei Jiang <superman.xpt@...il.com>, linux-kernel@...r.kernel.org,
 linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH] proc: proc_maps_open allow proc_mem_open to return NULL

On Fri,  8 Aug 2025 00:54:55 +0800 Jialin Wang <wjl.linux@...il.com> wrote:

> The commit 65c66047259f ("proc: fix the issue of proc_mem_open returning NULL")
> breaks `perf record -g -p PID` when profiling a kernel thread.
> 
> The strace of `perf record -g -p $(pgrep kswapd0)` shows:
> 
>   openat(AT_FDCWD, "/proc/65/task/65/maps", O_RDONLY) = -1 ESRCH (No such process)
> 
> This patch partially reverts the commit to fix it.

Thanks.  But "breaks" is a rather thin description of the problem!

Can you please describe the observed misbehavior fully?

> Fixes: 65c66047259f ("proc: fix the issue of proc_mem_open returning NULL")

Because we should backport this fix into 6.16.x -stable kernels.  The
-stable maintainers may wonder why we're requesting this.  Also, any
person who is having problems with their 6.16-based kernel will want
such a description so they can decide whether this fix might address
their problem.

Thanks.