On Fri, 19 May 2023 at 15:31, David Hildenbrand david@redhat.com wrote:
On 18.05.23 08:40, Xiaoming Ding (δΈζζ) wrote:
From 35fd062d5cbc4d182eee0183843cd6350d126788 Mon Sep 17 00:00:00 2001 From: Xiaoming Ding xiaoming.ding@mediatek.com 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@mediatek.com
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?
I am not aware of any limit that we put on pinning user-space 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?
So your observation is correct. With long term pinning we have to implement similar RLIMIT_MEMLOCK checks. Thanks for your insights here.
-Sumit
-- Thanks,
David / dhildenb