| From: Christian Brauner <brauner@kernel.org> |
| 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@kernel.org> |
| Reported-by: Hugh Dickins <hughd@google.com> |
| Link: https://lore.kernel.org/lkml/79eae9fe-7818-a65c-89c6-138b55d609a@google.com |
| Reviewed-by: Luis Chamberlain <mcgrof@kernel.org> |
| Cc: Adam Manzanares <a.manzanares@samsung.com> |
| Cc: Davidlohr Bueso <dave@stgolabs.net> |
| Cc: Kees Cook <keescook@chromium.org> |
| Cc: Matthew Wilcox (Oracle) <willy@infradead.org> |
| Cc: Pankaj Raghav <p.raghav@samsung.com> |
| Cc: Yosry Ahmed <yosryahmed@google.com> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| 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 |
| @@ -3582,6 +3582,10 @@ 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; |
| _ |
