On 18.05.23 08:40, Xiaoming Ding (丁晓明) wrote:
From 35fd062d5cbc4d182eee0183843cd6350d126788 Mon Sep 17 00:00:00 2001
From: Xiaoming Ding <xiaoming.ding@xxxxxxxxxxxx>
Date: Wed, 10 May 2023 10:15:23 +0800
Subject: [PATCH v2] tee: add FOLL_LONGTERM for CMA case when alloc shm
CMA is widely used on insufficient memory platform for
secure media playback case, and FOLL_LONGTERM will
avoid tee_shm alloc pages from CMA region.
without FOLL_LONGTERM, CMA region may alloc failed since
tee_shm has a chance to use it in advance.
modify is verified on OPTEE XTEST and kinds of secure + clear playback
Fixes: 033ddf12bcf5 ("tee: add register user memory")
Signed-off-by: Xiaoming Ding <xiaoming.ding@xxxxxxxxxxxx>
---
v1 -> v2: take off the ifdef and apply FOLL_LONGTERM by default
drivers/tee/tee_shm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
index 673cf0359494..38878e549ca4 100644
--- a/drivers/tee/tee_shm.c
+++ b/drivers/tee/tee_shm.c
@@ -257,7 +257,7 @@ register_shm_helper(struct tee_context *ctx,
unsigned long addr,
}
if (flags & TEE_SHM_USER_MAPPED)
- rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
+ rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE |
FOLL_LONGTERM,
shm->pages);
else
rc = shm_get_kernel_pages(start, num_pages, shm-
pages);
I didn't dive deeply into that code, but I can spot that we can end up
long-term pinning multiple pages -- possibly unbound or is there any
sane limit on the number of pages?
Take a look at io_uring/rsrc.c and how we account long-term pinned pages
against user->locked_vm/ctx->mm_account->pinned_vm in io_account_mem().
If user space could only end up pinning one or two pages via that
interface, ok. But it looks like this interface could be abused to
create real real trouble by unprivileged users that should be able to
long-term pin that many pages.
Am I missing something important (i.e., interface is only accessible by
privileged users) or should there be proper accounting and
RLIMIT_MEMLOCK checks?
--
Thanks,
David / dhildenb
