The patch titled
Subject: shmem: restrict noswap option to initial user namespace
has been added to the -mm mm-unstable branch. Its filename is
shmem-restrict-noswap-option-to-initial-user-namespace.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/shmem-restrict-noswap-option-to-initial-user-namespace.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Christian Brauner <brauner@xxxxxxxxxx>
Subject: shmem: restrict noswap option to initial user namespace
Date: Thu, 20 Apr 2023 10:57:43 +0200
Prevent tmpfs instances mounted in an unprivileged namespaces from evading
accounting of locked memory by using the "noswap" mount option.
Link: https://lkml.kernel.org/r/20230420-faxen-advokat-40abb4c1a152@brauner
Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
Reported-by: Hugh Dickins <hughd@xxxxxxxxxx>
Link: https://lore.kernel.org/lkml/79eae9fe-7818-a65c-89c6-138b55d609a@xxxxxxxxxx
Reviewed-by: Luis Chamberlain <mcgrof@xxxxxxxxxx>
Cc: Adam Manzanares <a.manzanares@xxxxxxxxxxx>
Cc: Davidlohr Bueso <dave@xxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Pankaj Raghav <p.raghav@xxxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/mm/shmem.c~shmem-restrict-noswap-option-to-initial-user-namespace
+++ a/mm/shmem.c
@@ -3712,6 +3712,10 @@ static int shmem_parse_one(struct fs_con
ctx->seen |= SHMEM_SEEN_INUMS;
break;
case Opt_noswap:
+ if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN)) {
+ return invalfc(fc,
+ "Turning off swap in unprivileged tmpfs mounts unsupported");
+ }
ctx->noswap = true;
ctx->seen |= SHMEM_SEEN_NOSWAP;
break;
_
Patches currently in -mm which might be from brauner@xxxxxxxxxx are
shmem-restrict-noswap-option-to-initial-user-namespace.patch
