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imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=YpHb8phY; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf24.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1781249764; b=ui0CHK0aNponE+7bPjqvY2chVCh9eyOjjRYFAgG16mMm2aIdwnIuRcYK5Skiq8iXolrcSY b+LtoUx99A+m9fCff6dwvKdPaR4ofq0RoqiWfvRyv2XHIM7/rcRLd8Yw7yXzwqOHCCLE42 vqHT1EKvHIAHAJsN94/dmUePN8eEr2Y= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id 191556008A; Fri, 12 Jun 2026 07:36:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AB1AF1F000E9; Fri, 12 Jun 2026 07:36:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1781249763; bh=kOX08Qpl3nLj8+/bGT7gMI+71ks0J39RDfqBI01e/bs=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=YpHb8phYvCXL//PMNv6jJibMmIvbuZmFBd81SZPjBSMR8ToRShtN3aXcZQR5xRGOF 5D1aoLZGabiAlDqIpuffzOCx97pcxQ9zSS0/JgxMXO0J1HfPqTEC0I21xlyTI22bSc rD+sjQ6+hPGHfZzV1cRQjhR1zP4JNTPuaZ+xJ/FAeHV1xlSYiVsoxlMVjMqbpvaDCn qXB2IXqiuMyKCLM/AHpVj7C5sVFvpbcSlfU8SBPVkLFWPROv5ffLzAAo4FsdEkp6Vv GDjbVyismAzQ8Yj41kuEmLVoZ66puCR7NZaY5e7pk5iSCZXrGdKNdkltMZnHJIkraK nd5WalUl+cWLw== Message-ID: <09ee2ea0-c93f-406c-b5af-1fe3a50c8989@kernel.org> Date: Fri, 12 Jun 2026 09:36:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/gup_test: fix race with PIN_LONGTERM_TEST ioctls To: Yunhui Cui , akpm@linux-foundation.org, jgg@ziepe.ca, jhubbard@nvidia.com, peterx@redhat.com, yang.lee@linux.alibaba.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: stable@vger.kernel.org References: <20260608025043.88087-1-cuiyunhui@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260608025043.88087-1-cuiyunhui@bytedance.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: B589B180003 X-Stat-Signature: 7zmkg9hahh3nsc1s5mwybgbg3fcc4ztn X-HE-Tag: 1781249764-589687 X-HE-Meta: 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 aX2ualMd dqsWRRysaMZ3InUJ+uYvI88CLKxxJ6KJJgTfE/aWslXkK3aLxBG9mA2NJp1LdQt2URsweUXej8WmjtKvolAIyJOOjyWEo8P5/dZCzbbs3wNb+T6Y+Kc3km36IL1tQPECNAZx0n8uYCR99QsvV/CVTSIru1U+FP34VqpO0AW21IVoqpHxztsG4Wg56EuNreYpr/8wzM2kd2uNZAftPCLj7uuPZ4beV2EudpgQY45TEBPjmUW5VZUd156BGIIhfHq/z0qYDYR7lPNqP7jrkMVmGRMtR2/8q2A3K74clLGTfkuJtgSlQLzVD1lICF09urTmLw8Vq+iPb0csOtok= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/8/26 04:50, Yunhui Cui wrote: > The PIN_LONGTERM_TEST helpers keep their state in global variables that > are protected by pin_longterm_test_mutex when accessed from ioctl(). > However, gup_test_release() calls pin_longterm_test_stop() without > holding that mutex. > > This can race with PIN_LONGTERM_TEST_STOP and let two callers operate on > the same pages array concurrently, corrupting the test state and possibly > freeing it twice: > > CPU 0 CPU 1 > ----- ----- > ioctl(PIN_LONGTERM_TEST_STOP) > mutex_lock(&pin_longterm_test_mutex) > pin_longterm_test_stop() > if (pin_longterm_test_pages) > kvfree(pin_longterm_test_pages) > > close() > gup_test_release() > pin_longterm_test_stop() > if (pin_longterm_test_pages) > kvfree(pin_longterm_test_pages) > > pin_longterm_test_pages = NULL > mutex_unlock(&pin_longterm_test_mutex) Okay, thinking about this some more ... I think what's really required here is that we have two separate "struct file", because otherwise release() cannot race with unlocked_ioctl(). Which is something we didn't expect when we added this functionality. I think the proper way to handle this is by moving the state to the "struct file", to actually cleanly allow concurrent usage. So instead, I think we should do the following (untested): >From 29e3d6fe00c4bd843d11bb548efa89bca478436c Mon Sep 17 00:00:00 2001 From: "David Hildenbrand (Arm)" Date: Fri, 12 Jun 2026 09:22:25 +0200 Subject: [PATCH] mm/gup_test: keep longterm pin state per file The pin longterm test currently stores its data globally, shared among multiple concurrent users of the interface (multiple open file descriptors -> multiple "struct file"'s). That makes the gup_test interface problematic to use concurrently: two users, such as concurrent selftest runs, can interfere with the same longterm pin state. While this has not been observed as a problem so far in practice, let's just handle it cleanly. There could be a way to trigger selftest failures by e.g., running the cow.c and gup_longerm.c selftests concurrently, but we usually run them sequentially. Let's add a "Fixes" tag to be safe. Fixes: c77369b437f9 ("mm/gup_test: start/stop/read functionality for PIN LONGTERM test") Signed-off-by: David Hildenbrand (Arm) --- mm/gup_test.c | 93 +++++++++++++++++++++++++++++++++------------------ 1 file changed, 61 insertions(+), 32 deletions(-) diff --git a/mm/gup_test.c b/mm/gup_test.c index 9dd48db897b9..16916056677e 100644 --- a/mm/gup_test.c +++ b/mm/gup_test.c @@ -8,6 +8,12 @@ #include #include "gup_test.h" +struct gup_test_data { + struct mutex longterm_mutex; + struct page **longterm_pages; + unsigned long longterm_nr_pages; +}; + static void put_back_pages(unsigned int cmd, struct page **pages, unsigned long nr_pages, unsigned int gup_test_flags) { @@ -204,23 +210,20 @@ static int __gup_test_ioctl(unsigned int cmd, return ret; } -static DEFINE_MUTEX(pin_longterm_test_mutex); -static struct page **pin_longterm_test_pages; -static unsigned long pin_longterm_test_nr_pages; - -static inline void pin_longterm_test_stop(void) +static inline void pin_longterm_test_stop(struct gup_test_data *data) { - if (pin_longterm_test_pages) { - if (pin_longterm_test_nr_pages) - unpin_user_pages(pin_longterm_test_pages, - pin_longterm_test_nr_pages); - kvfree(pin_longterm_test_pages); - pin_longterm_test_pages = NULL; - pin_longterm_test_nr_pages = 0; + if (data->longterm_pages) { + if (data->longterm_nr_pages) + unpin_user_pages(data->longterm_pages, + data->longterm_nr_pages); + kvfree(data->longterm_pages); + data->longterm_pages = NULL; + data->longterm_nr_pages = 0; } } -static inline int pin_longterm_test_start(unsigned long arg) +static inline int pin_longterm_test_start(struct gup_test_data *data, + unsigned long arg) { long nr_pages, cur_pages, addr, remaining_pages; int gup_flags = FOLL_LONGTERM; @@ -229,7 +232,7 @@ static inline int pin_longterm_test_start(unsigned long arg) int ret = 0; bool fast; - if (pin_longterm_test_pages) + if (data->longterm_pages) return -EINVAL; if (copy_from_user(&args, (void __user *)arg, sizeof(args))) @@ -259,12 +262,12 @@ static inline int pin_longterm_test_start(unsigned long arg) return -EINTR; } - pin_longterm_test_pages = pages; - pin_longterm_test_nr_pages = 0; + data->longterm_pages = pages; + data->longterm_nr_pages = 0; - while (nr_pages - pin_longterm_test_nr_pages) { - remaining_pages = nr_pages - pin_longterm_test_nr_pages; - addr = args.addr + pin_longterm_test_nr_pages * PAGE_SIZE; + while (nr_pages - data->longterm_nr_pages) { + remaining_pages = nr_pages - data->longterm_nr_pages; + addr = args.addr + data->longterm_nr_pages * PAGE_SIZE; if (fast) cur_pages = pin_user_pages_fast(addr, remaining_pages, @@ -273,11 +276,11 @@ static inline int pin_longterm_test_start(unsigned long arg) cur_pages = pin_user_pages(addr, remaining_pages, gup_flags, pages); if (cur_pages < 0) { - pin_longterm_test_stop(); + pin_longterm_test_stop(data); ret = cur_pages; break; } - pin_longterm_test_nr_pages += cur_pages; + data->longterm_nr_pages += cur_pages; pages += cur_pages; } @@ -286,19 +289,20 @@ static inline int pin_longterm_test_start(unsigned long arg) return ret; } -static inline int pin_longterm_test_read(unsigned long arg) +static inline int pin_longterm_test_read(struct gup_test_data *data, + unsigned long arg) { __u64 user_addr; unsigned long i; - if (!pin_longterm_test_pages) + if (!data->longterm_pages) return -EINVAL; if (copy_from_user(&user_addr, (void __user *)arg, sizeof(user_addr))) return -EFAULT; - for (i = 0; i < pin_longterm_test_nr_pages; i++) { - void *addr = kmap_local_page(pin_longterm_test_pages[i]); + for (i = 0; i < data->longterm_nr_pages; i++) { + void *addr = kmap_local_page(data->longterm_pages[i]); unsigned long ret; ret = copy_to_user((void __user *)(unsigned long)user_addr, addr, @@ -314,25 +318,26 @@ static inline int pin_longterm_test_read(unsigned long arg) static long pin_longterm_test_ioctl(struct file *filep, unsigned int cmd, unsigned long arg) { + struct gup_test_data *data = filep->private_data; int ret = -EINVAL; - if (mutex_lock_killable(&pin_longterm_test_mutex)) + if (mutex_lock_killable(&data->longterm_mutex)) return -EINTR; switch (cmd) { case PIN_LONGTERM_TEST_START: - ret = pin_longterm_test_start(arg); + ret = pin_longterm_test_start(data, arg); break; case PIN_LONGTERM_TEST_STOP: - pin_longterm_test_stop(); + pin_longterm_test_stop(data); ret = 0; break; case PIN_LONGTERM_TEST_READ: - ret = pin_longterm_test_read(arg); + ret = pin_longterm_test_read(data, arg); break; } - mutex_unlock(&pin_longterm_test_mutex); + mutex_unlock(&data->longterm_mutex); return ret; } @@ -371,15 +376,39 @@ static long gup_test_ioctl(struct file *filep, unsigned int cmd, return 0; } +static int gup_test_open(struct inode *inode, struct file *file) +{ + struct gup_test_data *data; + int ret; + + data = kzalloc(sizeof(*data), GFP_KERNEL); + if (!data) + return -ENOMEM; + + ret = nonseekable_open(inode, file); + if (ret) { + kfree(data); + return ret; + } + + mutex_init(&data->longterm_mutex); + file->private_data = data; + return 0; +} + static int gup_test_release(struct inode *inode, struct file *file) { - pin_longterm_test_stop(); + struct gup_test_data *data = file->private_data; + + pin_longterm_test_stop(data); + kfree(data); + file->private_data = NULL; return 0; } static const struct file_operations gup_test_fops = { - .open = nonseekable_open, + .open = gup_test_open, .unlocked_ioctl = gup_test_ioctl, .compat_ioctl = compat_ptr_ioctl, .release = gup_test_release, -- 2.43.0 Can you review+test that change? Thanks! -- Cheers, David