Re: [PATCH] man/man5/tmpfs.5: Specify that noswap may not be used within unprivileged user namespaces

[Alejandro Colomar <alx@kernel.org>]

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Hi Grayson,

> Date: 2026-10-19 19:51:12-0600
> From: Grayson Tinker <graysontinker@gmail.com>
>
> Since the tmpfs noswap option was added, the kernel has disallowed its use while
> within an unprivileged user namespace for security reasons. Document this restriction
> so users do not believe noswap to be available in every situation.
> 
> ref. linux.git 01106e140835ff94fdef79d66f166b87b0c89824 ("shmem: restrict noswap option to initial user namespace")
> 
> Signed-off-by: Grayson Tinker <graysontinker@gmail.com>

Thanks!  I've applied the patch.


Have a lovely night!
Alex

> ---
>  man/man5/tmpfs.5 | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/man/man5/tmpfs.5 b/man/man5/tmpfs.5
> index 10acbdcfa..a904db2c8 100644
> --- a/man/man5/tmpfs.5
> +++ b/man/man5/tmpfs.5
> @@ -109,6 +109,10 @@ but not a % suffix.
>  Disables swap.
>  Remounts must respect the original settings.
>  By default swap is enabled.
> +.IP
> +.\" commit 01106e140835ff94fdef79d66f166b87b0c89824
> +.B noswap
> +is not available while within an unprivileged user namespace.
>  .TP
>  .BR mode =\f[I]mode\f[]
>  Set initial permissions of the root directory.
> 
> Range-diff:
> -:  --------- > 1:  b3b2becca man/man5/tmpfs.5: Specify that noswap may not be used within unprivileged user namespaces
> -- 
> 2.55.0
> 

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

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