[dramforever@live.com: [PATCH] man/man5/proc_pid.5: Clarify which user namespace affects permissions]

[Alejandro Colomar <alx@kernel.org>]

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Hi Vivian,

Can you please confirm this is you?  I received this patch from an
address that doesn't match the one I see in your kernel commits, and
when I replied to <dramforever@live.com>, the message bounced.  I'm just
checking.  See patch from the @live.com address below.


Have a lovely night!
Alex

----- Forwarded message from Vivian Wang <dramforever@live.com> -----

Date: Mon, 16 Mar 2026 22:07:52 +0800
From: Vivian Wang <dramforever@live.com>
To: Alejandro Colomar <alx@kernel.org>
Cc: linux-man@vger.kernel.org, Michael Kerrisk <mtk.manpages@gmail.com>
Subject: [PATCH] man/man5/proc_pid.5: Clarify which user namespace affects
 permissions
Message-ID: <OSCPR01MB134682A1A80B8C9FB71CBA64DC640A@OSCPR01MB13468.jpnprd01.prod.outlook.com>
User-Agent: Mozilla Thunderbird

A more careful reading of fs/proc/base.c (since v4.11, as of v7.0-rc1)
reveals that it is not task->cred->user_ns that is checked, but
task->mm->user_ns, which is set during execve(2) (and copied over in
fork(2) and so on) [1], and is the correct user namespace to check for
ptrace-related purposes. Clarify the relevant text.

[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=bfedb589252c01fa505ac9f6f2a3d5d68d707ef4

Fixes: ae636827 ("proc.5: Fix description of /proc/PID/* ownership to account for user namespaces")
Signed-off-by: Vivian Wang <dramforever@live.com>
---
 man/man5/proc_pid.5 | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/man/man5/proc_pid.5 b/man/man5/proc_pid.5
index eac97fa1d..2fe35bd09 100644
--- a/man/man5/proc_pid.5
+++ b/man/man5/proc_pid.5
@@ -30,7 +30,9 @@ Before Linux 4.11,
 meant the "global" root user ID and group ID
 (i.e., UID 0 and GID 0 in the initial user namespace).
 Since Linux 4.11,
-if the process is in a noninitial user namespace that has a
+if when the last time the process called
+.BR execve (2),
+it was in a noninitial user namespace that has a
 valid mapping for user (group) ID 0 inside the namespace, then
 the user (group) ownership of the files under
 .IR /proc/ pid
-- 
2.53.0



----- End forwarded message -----

-- 
<https://www.alejandro-colomar.es>

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