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authorChristian Brauner <brauner@kernel.org>2023-04-20 11:57:43 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-04-27 23:42:16 +0300
commit01106e140835ff94fdef79d66f166b87b0c89824 (patch)
tree4a0cfc25e0915655523eeb108e47cae5c61ac3e6 /mm
parent0175ab610c2df7c21d93e4bd63b4e67cfa86737c (diff)
downloadlinux-01106e140835ff94fdef79d66f166b87b0c89824.tar.xz
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@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>
Diffstat (limited to 'mm')
-rw-r--r--mm/shmem.c4
1 files changed, 4 insertions, 0 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index 3531ebb3494e..1a6263f54ada 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -3582,6 +3582,10 @@ static int shmem_parse_one(struct fs_context *fc, struct fs_parameter *param)
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;