Commit 01106e14 authored by Christian Brauner's avatar Christian Brauner Committed by Andrew Morton

shmem: restrict noswap option to initial user namespace

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@braunerSigned-off-by: default avatarChristian Brauner <brauner@kernel.org>
Reported-by: default avatarHugh Dickins <hughd@google.com>
  Link: https://lore.kernel.org/lkml/79eae9fe-7818-a65c-89c6-138b55d609a@google.comReviewed-by: default avatarLuis 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 0175ab61
...@@ -3582,6 +3582,10 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param) ...@@ -3582,6 +3582,10 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
ctx->seen |= SHMEM_SEEN_INUMS; ctx->seen |= SHMEM_SEEN_INUMS;
break; break;
case Opt_noswap: 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->noswap = true;
ctx->seen |= SHMEM_SEEN_NOSWAP; ctx->seen |= SHMEM_SEEN_NOSWAP;
break; break;
......
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