From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8397F5172DA; Tue, 13 Oct 2026 14:40:50 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791902452; cv=none; b=GeMcXyX3jUUeS/Sdz+6e9A2ru8kPQez0H+fXGfKnu7iAvg0e3/3fDcD2lseVE+YEtbDWstOnbKZNDxkFukhLHv+uIQUsoapvZx9m85kZxEZjx6o7nxC5dB19lCyoCqPibW5OXOezyQ+mIgMbIGbgyORRcoIrHYfyoEUfljqMQwk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791902452; c=relaxed/simple; bh=tshp6hN17mH0meZuCKVUXcZoCinEb1JlKAYw+wtFHrU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=AEdF7qGYaCjzzdoNIcbetLfG4xxl2MQW+p6Cpa5J50RuEA0npOdlCKm3QcxdqbH1S84RFwtveHrNnYcqhxFmNeYJucby2vtHdYEv8DHE0bq6pcbAn6W0Tv4rPlkgG+nENWnaMzk21Z8giD778PFlb87SlTia0WAdF/6n58yy/DE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=E3dxMwqL; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="E3dxMwqL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D2FB81F000FF; Tue, 13 Oct 2026 14:40:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791902450; bh=JMF/X4p2JMQOAWL5F8hcgnR0xRgqfvQmfw3SYOWs+Bc=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=E3dxMwqLMttYe0HqZS0dZWPQZ5GG3zyuI0bjf3NPCgljWbcwXvEdkz5wNfUKIR9uO zrID0Xq18gpwNsFxSeaTpXMu8IwYvTbAvA58g/QChfUKY8hGkNGiN4cQV5qWD6opX+ czt4bQbb2TFIbQ+a7fGK/AISz3uh4NW3NwTCV79PSHfDdS+t6BHS/IGf34Y/d5KAns M3gTuKmkeJop2tA3nk1lKWpdnTe5rxUBYy9KSRVGqkiyJWnz1hBMENfuevLW/x8W+N dnMl3rvQi04aFvYZ475GaDry7zGNs8sGWJ6xqhJ3Olx/m16Qsr2Sf2cBNTLEwlys6f Ia9OFnVh7q93g== Message-ID: Date: Tue, 13 Oct 2026 16:40:43 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] fs/proc/task_mmu: fix lost maps entries above 2^63 To: Stian Halseth , Andrew Morton , Suren Baghdasaryan Cc: "Liam R. Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , Pedro Falcato , Andreas Larsson , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <20261011162019.922436-1-stian@itx.no> 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: <20261011162019.922436-1-stian@itx.no> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 10/11/26 18:20, Stian Halseth wrote: > When a read of /proc/pid/{maps,smaps,numa_maps} resumes, m_start() > rewinds *ppos to priv->last_pos so that the vma which did not fit into > the previous buffer is shown again. It only does so for last_addr > 0, > meaning to exclude the start of the file and SENTINEL_VMA_GATE, but > last_addr is a signed loff_t holding a vm_end. sparc64 maps shared > libraries, anonymous memory and the stack above 0x8000000000000000, so > the rewind does not happen there and one entry is lost at every read() > boundary. > > Reading the maps file of a process with read sizes from 64 to 8192 > bytes in steps of 64 loses lines at 126 of the 128 sizes, smaps at 123 > and numa_maps at 97, and the proc-maps-race selftest fails 4 of its 6 > tests. Python's sys.remote_exec() reads maps with fgets() and fails > intermittently when it misses the libpython data mapping. > > Test for the two values that are not a vma end instead. > > Fixes: 5631da56c9a87 ("fs/proc/task_mmu: read proc/pid/maps under per-vma lock") > Closes: https://github.com/sparclinux/issues/issues/111 > Cc: stable@vger.kernel.org > Signed-off-by: Stian Halseth > --- > > Notes: > Tested on a SPARC T7-1 (sun4v, 7.3-rc5), a T4-1 (7.2.9) and a Sun Fire > V240 (sun4u, 7.3-rc5): no lost lines at any read size afterwards, and > Python's sys.remote_exec() test passes 20/20. On an amd64 KVM guest maps, > smaps, numa_maps and the proc selftests are unchanged. > > fs/proc/task_mmu.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index 5c54aebe21182..cdce513edcb1d 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -339,7 +339,7 @@ static void *m_start(struct seq_file *m, loff_t *ppos) > * Reset current position if last_addr was set before > * and it's not a sentinel. > */ > - if (last_addr > 0) > + if (last_addr && last_addr != SENTINEL_VMA_GATE) > *ppos = last_addr = priv->last_pos; > vma_iter_init(&priv->iter, mm, (unsigned long)last_addr); > hold_task_mempolicy(priv); I hope Suren can review as well. Would it be cleaner to reject any special values, that is, SENTINEL_VMA_END and SENTINEL_VMA_GATE? That would match the comment and the previous code idea: exclude only 0 and sentinels. Could consider a simple addr_is_sentinel() helper. -- Cheers, David