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 54EBC2DF13A; Fri, 17 Jul 2026 10:46:53 +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=1784285214; cv=none; b=WETHhmgTv8INNksdym7n9bklOK5J3re/Sxmaw9/2bJho77D2QOIc4S4arGer2UfZNi7DXpo+ktMp26oUkUEooG/Lj0bI21leq+TTs4EZZnz5v19B/tcBkio0ZTDD2zRUHW2der84MuS2xM3svUKHzF+RUb4U7mw8w734gGs5JOE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784285214; c=relaxed/simple; bh=CIQg1p69wkbqKNHwGP78SGGMMpbznLsqUCdm42Z4f7g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Jtx4iY0pSqem8DZe1jrb6d05i99mtlfp1LTIxlKx7DUQ+2d6ZmPQR6kwe3R/HzssJMPhWQgI6oicDNE8VM0QZxHgVUZc001z7NnaRbz+GQHSNvQv6r0bhX5YHePgJPnTWCoQCWYRbL9XJoLmUTWbLelJ0c5ufsX3NwmTjx+gMiQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=hzkUquUH; 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="hzkUquUH" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5B27C1F000E9; Fri, 17 Jul 2026 10:46:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784285213; bh=3H4YLFiWf6/et6CXjfq0ULsNF5gxpRV9YLwLUMKI6wQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=hzkUquUHODHWzH8JpKjAUClJJpSoP2sxVLRw9lRKpXDE8aev3+TxKlI+vMvW0QWul L89qf7kK+KUSZ/2CPyeHYehcd62RbBWdUu9PB1AZ6zS6fZt3AZwjRPOMzKrbd5uzlc jLXCChY7qhZEHgfFtw2bqKisOGKE5b1V6055GqxzSZ2n/NfRnzv0z1yDat0/lILAw8 uN3HU6gVTgF6EHoyv1xSxgZ9VZb/PM0NbRuu34jGywpvBSL3sniln6rKtfLWCli0S7 fqO4uAmOtGS1lTZxW5hZZfx9u4pMU3fRV5d+wzQU9GZonew+7oDD8as7UDkDUAzgWZ /wpT+AHMmI2zw== Message-ID: Date: Fri, 17 Jul 2026 11:46:49 +0100 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 2/3] mm/mseal: limit scope of mseal address zero to address zero To: "Lorenzo Stoakes (ARM)" , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato , Alexander Viro , Christian Brauner , Jan Kara , Kees Cook , Mike Rapoport , Suren Baghdasaryan , Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org References: <20260716-mseal-fixups-v1-0-3a9609bf041b@kernel.org> <20260716-mseal-fixups-v1-2-3a9609bf041b@kernel.org> 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: <20260716-mseal-fixups-v1-2-3a9609bf041b@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/16/26 15:43, Lorenzo Stoakes (ARM) wrote: > Commit 44f65d900698 ("binfmt_elf: mseal address zero") unconditionally > provided do_mseal() to any internal kernel caller in order to address a > corner case slated for possible removal. > > It also incorrectly attempts to mseal() without checking to see whether the > mapping even succeeded. > > Restrict the scope to the corner case by providing mseal_mmap_page_zero() > which asserts the MMAP_PAGE_ZERO personality. > > Avoid unnecessary checks in the start, end range by abstracting the actual > mseal()'ing to mseal() and have mseal_mmap_page_zero() call that instead. > > Only try to seal the VMA if we mapped the VMA. > > Signed-off-by: Lorenzo Stoakes (ARM) > --- > fs/binfmt_elf.c | 7 ++----- > include/linux/mm.h | 8 ++------ > mm/mseal.c | 48 +++++++++++++++++++++++++++++++++++------------- > 3 files changed, 39 insertions(+), 24 deletions(-) > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c > index 16a56b6b3f6c..e3131a311995 100644 > --- a/fs/binfmt_elf.c > +++ b/fs/binfmt_elf.c > @@ -1353,11 +1353,8 @@ static int load_elf_binary(struct linux_binprm *bprm) > emulate the SVr4 behavior. Sigh. */ > error = vm_mmap(NULL, 0, PAGE_SIZE, PROT_READ | PROT_EXEC, > MAP_FIXED | MAP_PRIVATE, 0); > - > - retval = do_mseal(0, PAGE_SIZE, 0); > - if (retval) > - pr_warn_ratelimited("pid=%d, couldn't seal address 0, ret=%d.\n", > - task_pid_nr(current), retval); > + if (!error) > + mseal_mmap_page_zero(); > } > > regs = current_pt_regs(); > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 550fb92957d1..87feaa5a2b78 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -5291,13 +5291,9 @@ int reserve_mem_find_by_name(const char *name, phys_addr_t *start, phys_addr_t * > int reserve_mem_release_by_name(const char *name); > > #ifdef CONFIG_64BIT > -int do_mseal(unsigned long start, size_t len_in, unsigned long flags); > +void mseal_mmap_page_zero(void); do_mseal() gone here, nice. > #else > -static inline int do_mseal(unsigned long start, size_t len_in, unsigned long flags) > -{ > - /* noop on 32 bit */ > - return 0; > -} > +static inline void mseal_mmap_page_zero(void) {} > #endif > > /* > diff --git a/mm/mseal.c b/mm/mseal.c > index 207fea89c61e..5930551d84f2 100644 > --- a/mm/mseal.c > +++ b/mm/mseal.c > @@ -32,7 +32,7 @@ static bool range_contains_unmapped(unsigned long start, unsigned long end) > return prev_end < end; > } > > -static int mseal_apply(unsigned long start, unsigned long end) > +static int __mseal(unsigned long start, unsigned long end) > { > struct vm_area_struct *vma, *prev; > VMA_ITERATOR(vmi, current->mm, start); > @@ -66,6 +66,38 @@ static int mseal_apply(unsigned long start, unsigned long end) > return 0; > } > > +static int mseal(unsigned long start, unsigned long end) mseal_range() could be indeed nicer. But do_mseal() is now a pure helper for "SYSCALL_DEFINE3(mseal" only ...could we simply inline do_mseal into SYSCALL_DEFINE3(mseal)? We could do that separately, ofc. -- Cheers, David