Re: [PATCH v4] tee: Use iov_iter to better support shared buffer registration

From: Arnaud POULIQUEN
Date: Thu Nov 30 2023 - 08:18:51 EST



On 11/30/23 13:00, Sumit Garg wrote:
> On Thu, 30 Nov 2023 at 14:38, Arnaud POULIQUEN
> <arnaud.pouliquen@xxxxxxxxxxx> wrote:
>>
>>
>>
>> On 11/30/23 08:54, Sumit Garg wrote:
>>> On Wed, 29 Nov 2023 at 22:15, Arnaud Pouliquen
>>> <arnaud.pouliquen@xxxxxxxxxxx> wrote:
>>>>
>>>> Currently it's not possible to register kernel buffers with TEE
>>>> which are allocated via vmalloc.
>>>>
>>>> Use iov_iter and associated helper functions to manage the page
>>>> registration for all type of memories.
>>>>
>>>> Suggested-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
>>>> Signed-off-by: Arnaud Pouliquen <arnaud.pouliquen@xxxxxxxxxxx>
>>>> ---
>>>> Update from V3 to V4:
>>>> - improve commit message,
>>>> - use import_ubuf() instead of iov_iter_init(),
>>>> - move shm_get_kernel_pages in register_shm_helper,
>>>> - put back untagged_addr in register_shm_helper(),
>>>> - move the comment related to pin pages from shm_get_kernel_pages()
>>>> to register_shm_helper().
>>>>
>>>> Update from V2 to V3:
>>>> - break lines longer than 80 columns.
>>>>
>>>> Update from V1 to V2:
>>>> - replace ITER_SOURCE by ITER_DEST flag in tee_shm_register_user_buf(),
>>>> - replace IS_ERR_OR NULL(shm) by IS_ERR(shm) in tee_shm_register_user_buf().
>>>>
>>>> V1:
>>>> The support of buffer registration allocated with vmalloc is no more
>>>> available since c83900393aa1 ("tee: Remove vmalloc page support").
>>>>
>>>> This patch is an alternative to a revert and resulted from a discussion
>>>> with Christopher Hellwig [1].
>>>>
>>>> This patch has been tested using xtest tool in optee qemu environment [2]
>>>> and using the series related to the remoteproc tee that should be
>>>> proposed soon [3].
>>>>
>>>> References:
>>>> [1] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@xxxxxxxxxxx/T/#m8ec683c44fcd9b69c2aee42eaed0793afac9dd18in
>>>> [2] https://optee.readthedocs.io/en/latest/building/devices/qemu.html#build-instructions
>>>> [3] https://lore.kernel.org/linux-arm-kernel/18a8528d-7d9d-6ed0-0045-5ee47dd39fb2@xxxxxxxxxxx/T/#maca0a1fc897aadd54c7deac432e11473fe970d1d
>>>> ---
>>>> drivers/tee/tee_shm.c | 83 ++++++++++++++++++++++++-------------------
>>>> 1 file changed, 46 insertions(+), 37 deletions(-)
>>>>
>>>> diff --git a/drivers/tee/tee_shm.c b/drivers/tee/tee_shm.c
>>>> index 673cf0359494..ac73e8143233 100644
>>>> --- a/drivers/tee/tee_shm.c
>>>> +++ b/drivers/tee/tee_shm.c
>>>> @@ -22,23 +22,12 @@ static void shm_put_kernel_pages(struct page **pages, size_t page_count)
>>>> put_page(pages[n]);
>>>> }
>>>>
>>>> -static int shm_get_kernel_pages(unsigned long start, size_t page_count,
>>>> - struct page **pages)
>>>> +static void shm_get_kernel_pages(struct page **pages, size_t page_count)
>>>> {
>>>> - struct page *page;
>>>> size_t n;
>>>>
>>>> - if (WARN_ON_ONCE(is_vmalloc_addr((void *)start) ||
>>>> - is_kmap_addr((void *)start)))
>>>> - return -EINVAL;
>>>> -
>>>> - page = virt_to_page((void *)start);
>>>> - for (n = 0; n < page_count; n++) {
>>>> - pages[n] = page + n;
>>>> + for (n = 0; n < page_count; n++)
>>>> get_page(pages[n]);
>>>> - }
>>>> -
>>>> - return page_count;
>>>> }
>>>>
>>>> static void release_registered_pages(struct tee_shm *shm)
>>>> @@ -214,13 +203,14 @@ struct tee_shm *tee_shm_alloc_priv_buf(struct tee_context *ctx, size_t size)
>>>> EXPORT_SYMBOL_GPL(tee_shm_alloc_priv_buf);
>>>>
>>>> static struct tee_shm *
>>>> -register_shm_helper(struct tee_context *ctx, unsigned long addr,
>>>> - size_t length, u32 flags, int id)
>>>> +register_shm_helper(struct tee_context *ctx, struct iov_iter *iter, u32 flags,
>>>> + int id)
>>>> {
>>>> struct tee_device *teedev = ctx->teedev;
>>>> struct tee_shm *shm;
>>>> - unsigned long start;
>>>> - size_t num_pages;
>>>> + unsigned long start, addr;
>>>> + size_t num_pages, off;
>>>> + ssize_t len;
>>>> void *ret;
>>>> int rc;
>>>>
>>>> @@ -245,31 +235,38 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>>>> shm->flags = flags;
>>>> shm->ctx = ctx;
>>>> shm->id = id;
>>>> - addr = untagged_addr(addr);
>>>> + addr = untagged_addr((unsigned long)iter_iov_addr(iter));
>>>> start = rounddown(addr, PAGE_SIZE);
>>>> - shm->offset = addr - start;
>>>> - shm->size = length;
>>>> - num_pages = (roundup(addr + length, PAGE_SIZE) - start) / PAGE_SIZE;
>>>> + num_pages = iov_iter_npages(iter, INT_MAX);
>>>> + if (!num_pages) {
>>>> + ret = ERR_PTR(-ENOMEM);
>>>> + goto err_ctx_put;
>>>> + }
>>>> +
>>>> shm->pages = kcalloc(num_pages, sizeof(*shm->pages), GFP_KERNEL);
>>>> if (!shm->pages) {
>>>> ret = ERR_PTR(-ENOMEM);
>>>> goto err_free_shm;
>>>> }
>>>>
>>>> - if (flags & TEE_SHM_USER_MAPPED)
>>>> - rc = pin_user_pages_fast(start, num_pages, FOLL_WRITE,
>>>> - shm->pages);
>>>> - else
>>>> - rc = shm_get_kernel_pages(start, num_pages, shm->pages);
>>>> - if (rc > 0)
>>>> - shm->num_pages = rc;
>>>> - if (rc != num_pages) {
>>>> - if (rc >= 0)
>>>> - rc = -ENOMEM;
>>>> - ret = ERR_PTR(rc);
>>>> - goto err_put_shm_pages;
>>>> + len = iov_iter_extract_pages(iter, &shm->pages, LONG_MAX, num_pages, 0,
>>>> + &off);
>>>> + if (unlikely(len <= 0)) {
>>>> + ret = len ? ERR_PTR(len) : ERR_PTR(-ENOMEM);
>>>> + goto err_free_shm_pages;
>>>> }
>>>>
>>>> + /*
>>>> + * iov_iter_extract_kvec_pages does not get reference on the pages,
>>>> + * get a pin on them.
>>>
>>> I think you meant: "get a reference on them". But I don't see the
>>> value of this comment since iov_iter_extract_kvec_pages() already has
>>> been commented properly as follows:
>>>
>>> /*
>>> * Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
>>> * This does not get references on the pages, nor does it get a pin on them.
>>> */
>>>
>>
>> I spent some time debugging this part. Since we use the same API for both user
>> and kernel buffers, we wouldn't expect to have any specific actions to take.
>> Therefore, I thought it would be helpful to add a comment explaining the reason
>> for this specific code, rather than go deeper into iov_iter to understand it.
>>
>
> Fair enough, let's keep it with s/pin/reference/.
>
>> But if you don't see the value, I can remove the comment.
>>
>>>> + */
>>>> + if (iov_iter_is_kvec(iter))
>>>> + shm_get_kernel_pages(shm->pages, num_pages);
>>>> +
>>>> + shm->offset = off;
>>>> + shm->size = len;
>>>> + shm->num_pages = num_pages;
>>>> +
>>>> rc = teedev->desc->ops->shm_register(ctx, shm, shm->pages,
>>>> shm->num_pages, start);
>>>> if (rc) {
>>>> @@ -279,10 +276,11 @@ register_shm_helper(struct tee_context *ctx, unsigned long addr,
>>>>
>>>> return shm;
>>>> err_put_shm_pages:
>>>> - if (flags & TEE_SHM_USER_MAPPED)
>>>> + if (!iov_iter_is_kvec(iter))
>>>> unpin_user_pages(shm->pages, shm->num_pages);
>>>> else
>>>> shm_put_kernel_pages(shm->pages, shm->num_pages);
>>>> +err_free_shm_pages:
>>>> kfree(shm->pages);
>>>> err_free_shm:
>>>> kfree(shm);
>>>> @@ -307,8 +305,9 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>>>> u32 flags = TEE_SHM_USER_MAPPED | TEE_SHM_DYNAMIC;
>>>> struct tee_device *teedev = ctx->teedev;
>>>> struct tee_shm *shm;
>>>> + struct iov_iter iter;
>>>> void *ret;
>>>> - int id;
>>>> + int id, err;
>>>>
>>>> if (!access_ok((void __user *)addr, length))
>>>> return ERR_PTR(-EFAULT);
>>>> @@ -319,7 +318,11 @@ struct tee_shm *tee_shm_register_user_buf(struct tee_context *ctx,
>>>> if (id < 0)
>>>> return ERR_PTR(id);
>>>>
>>>> - shm = register_shm_helper(ctx, addr, length, flags, id);
>>>> + err = import_ubuf(ITER_DEST, (void __user *)addr, length, &iter);
>>>
>>> As I mentioned in a previous review, import_ubuf() already does the
>>> access_ok() check, so we don't need the extra access_ok() check above.
>>> Also, you should move import_ubuf() to be the first invocation within
>>> this API.
>>
>> My apologies, I re-added import_ubuf() during testing to debug an issue and
>
> I suppose you intended to mention access_ok() here, BTW, no worries :).

Re-running xtest after removing the access_ok() I have a crash in
regression_5006.3 Allocate_out_of_memory

[ 89.258100] ------------[ cut here ]------------
[ 89.258377] WARNING: CPU: 1 PID: 134 at mm/page_alloc.c:4402
__alloc_pages+0x674/0xd14
[ 89.258988] Modules linked in:
[ 89.259554] CPU: 1 PID: 134 Comm: xtest Not tainted 6.6.0-g1ebcc18a80d7-dirty #69
[ 89.259763] Hardware name: linux,dummy-virt (DT)
[ 89.259977] pstate: 21400005 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
[ 89.260143] pc : __alloc_pages+0x674/0xd14
[ 89.260252] lr : alloc_pages+0xac/0x160
[ 89.260364] sp : ffff8000803f3a30
[ 89.260437] x29: ffff8000803f3a30 x28: ffff8000803f3d70 x27: 0000000000000000
[ 89.260705] x26: 000000000000000b x25: 0000000000000000 x24: ffff000000178000
[ 89.260847] x23: ffff00003f52b720 x22: ffff000001442720 x21: 0000000000000000
[ 89.261022] x20: 000000000000000b x19: 0000000000000000 x18: ffff8000803f3b78
[ 89.261162] x17: 0000000000000000 x16: ffffa7a428b67660 x15: 0000ffff63ffffff
[ 89.261348] x14: 0000000000000008 x13: 1fffe00000a4c421 x12: ffff8000803f3b78
[ 89.261528] x11: ffff000005262100 x10: ffff000005262108 x9 : ffff00000526210c
[ 89.261739] x8 : 0000aaab0a97c000 x7 : 0000aaab0a90e000 x6 : ffff000005262150
[ 89.261920] x5 : 0000000000000000 x4 : ffff000000976740 x3 : 0000000000000000
[ 89.262098] x2 : 0000000000000000 x1 : 0000000000000001 x0 : ffffa7a429daf000
[ 89.262340] Call trace:
[ 89.262921] __alloc_pages+0x674/0xd14
[ 89.263262] alloc_pages+0xac/0x160
[ 89.263373] alloc_pages_exact+0x48/0x94
[ 89.263464] optee_shm_register+0xa8/0x1f4
[ 89.263591] register_shm_helper+0x1bc/0x28c
[ 89.263687] tee_shm_register_user_buf+0xb8/0x128
[ 89.263816] tee_ioctl+0xbc/0xfa0
[ 89.263915] __arm64_sys_ioctl+0xa8/0xec
[ 89.264053] invoke_syscall+0x48/0x114
[ 89.264173] el0_svc_common.constprop.0+0x40/0xe8
[ 89.264321] do_el0_svc+0x20/0x2c
[ 89.264488] el0_svc+0x40/0xf4
[ 89.264578] el0t_64_sync_handler+0x13c/0x158
[ 89.264714] el0t_64_sync+0x190/0x194
[ 89.265003] ---[ end trace 0000000000000000 ]---


The issue is that, in import_ubuf(), it updates the length [1], making the

access_ok() succeed and leading to an issue later in the page allocation process.

To fix, I propose to add a test in tee_shm_register_user_buf() after calling

import_ubuf()

if (length != iter_iov_len(&iter))
return ERR_PTR(-EFAULT);


Would it be ok for you ? I'm afraid of side effects if I update import_ubuf()...

[1] https://elixir.bootlin.com/linux/latest/source/lib/iov_iter.c#L1553

Regards,
Arnaud


>
> -Sumit
>
>> forgot to
>> remove it afterwards.
>>
>> Thanks and regards,
>> Arnaud
>>
>>>
>>> -Sumit
>>>
>>>> + if (err)
>>>> + return ERR_PTR(err);
>>>> +
>>>> + shm = register_shm_helper(ctx, &iter, flags, id);
>>>> if (IS_ERR(shm)) {
>>>> mutex_lock(&teedev->mutex);
>>>> idr_remove(&teedev->idr, id);
>>>> @@ -352,8 +355,14 @@ struct tee_shm *tee_shm_register_kernel_buf(struct tee_context *ctx,
>>>> void *addr, size_t length)
>>>> {
>>>> u32 flags = TEE_SHM_DYNAMIC;
>>>> + struct kvec kvec;
>>>> + struct iov_iter iter;
>>>> +
>>>> + kvec.iov_base = addr;
>>>> + kvec.iov_len = length;
>>>> + iov_iter_kvec(&iter, ITER_DEST, &kvec, 1, length);
>>>>
>>>> - return register_shm_helper(ctx, (unsigned long)addr, length, flags, -1);
>>>> + return register_shm_helper(ctx, &iter, flags, -1);
>>>> }
>>>> EXPORT_SYMBOL_GPL(tee_shm_register_kernel_buf);
>>>>
>>>> --
>>>> 2.25.1
>>>>