linux-kernel - Re: [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory syscalls

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Date:   Wed, 19 Jun 2019 10:46:17 -0600
From:   Khalid Aziz <khalid.aziz@...cle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
        dri-devel@...ts.freedesktop.org, linux-rdma@...r.kernel.org,
        linux-media@...r.kernel.org, kvm@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Yishai Hadas <yishaih@...lanox.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Alexander Deucher <Alexander.Deucher@....com>,
        Christian Koenig <Christian.Koenig@....com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jens Wiklander <jens.wiklander@...aro.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Leon Romanovsky <leon@...nel.org>,
        Luc Van Oostenryck <luc.vanoostenryck@...il.com>,
        Dave Martin <Dave.Martin@....com>, enh <enh@...gle.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christoph Hellwig <hch@...radead.org>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Kostya Serebryany <kcc@...gle.com>,
        Evgeniy Stepanov <eugenis@...gle.com>,
        Lee Smith <Lee.Smith@....com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Szabolcs Nagy <Szabolcs.Nagy@....com>
Subject: Re: [PATCH v17 04/15] mm, arm64: untag user pointers passed to memory
 syscalls

On 6/19/19 9:55 AM, Khalid Aziz wrote:
> On 6/12/19 5:43 AM, Andrey Konovalov wrote:
>> This patch is a part of a series that extends arm64 kernel ABI to allow to
>> pass tagged user pointers (with the top byte set to something else other
>> than 0x00) as syscall arguments.
>>
>> This patch allows tagged pointers to be passed to the following memory
>> syscalls: get_mempolicy, madvise, mbind, mincore, mlock, mlock2, mprotect,
>> mremap, msync, munlock, move_pages.
>>
>> The mmap and mremap syscalls do not currently accept tagged addresses.
>> Architectures may interpret the tag as a background colour for the
>> corresponding vma.
>>
>> Reviewed-by: Catalin Marinas <catalin.marinas@....com>
>> Reviewed-by: Kees Cook <keescook@...omium.org>
>> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
>> ---
> 
> Reviewed-by: Khalid Aziz <khalid.aziz@...cle.com>
> 
> 

I would also recommend updating commit log for all the patches in this
series that are changing files under mm/ as opposed to arch/arm64 to not
reference arm64 kernel ABI since the change applies to every
architecture. So something along the lines of "This patch is part of a
series that extends kernel ABI to allow......."

--
Khalid


>>  mm/madvise.c   | 2 ++
>>  mm/mempolicy.c | 3 +++
>>  mm/migrate.c   | 2 +-
>>  mm/mincore.c   | 2 ++
>>  mm/mlock.c     | 4 ++++
>>  mm/mprotect.c  | 2 ++
>>  mm/mremap.c    | 7 +++++++
>>  mm/msync.c     | 2 ++
>>  8 files changed, 23 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/madvise.c b/mm/madvise.c
>> index 628022e674a7..39b82f8a698f 100644
>> --- a/mm/madvise.c
>> +++ b/mm/madvise.c
>> @@ -810,6 +810,8 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
>>  	size_t len;
>>  	struct blk_plug plug;
>>  
>> +	start = untagged_addr(start);
>> +
>>  	if (!madvise_behavior_valid(behavior))
>>  		return error;
>>  
>> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
>> index 01600d80ae01..78e0a88b2680 100644
>> --- a/mm/mempolicy.c
>> +++ b/mm/mempolicy.c
>> @@ -1360,6 +1360,7 @@ static long kernel_mbind(unsigned long start, unsigned long len,
>>  	int err;
>>  	unsigned short mode_flags;
>>  
>> +	start = untagged_addr(start);
>>  	mode_flags = mode & MPOL_MODE_FLAGS;
>>  	mode &= ~MPOL_MODE_FLAGS;
>>  	if (mode >= MPOL_MAX)
>> @@ -1517,6 +1518,8 @@ static int kernel_get_mempolicy(int __user *policy,
>>  	int uninitialized_var(pval);
>>  	nodemask_t nodes;
>>  
>> +	addr = untagged_addr(addr);
>> +
>>  	if (nmask != NULL && maxnode < nr_node_ids)
>>  		return -EINVAL;
>>  
>> diff --git a/mm/migrate.c b/mm/migrate.c
>> index f2ecc2855a12..d22c45cf36b2 100644
>> --- a/mm/migrate.c
>> +++ b/mm/migrate.c
>> @@ -1616,7 +1616,7 @@ static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes,
>>  			goto out_flush;
>>  		if (get_user(node, nodes + i))
>>  			goto out_flush;
>> -		addr = (unsigned long)p;
>> +		addr = (unsigned long)untagged_addr(p);
>>  
>>  		err = -ENODEV;
>>  		if (node < 0 || node >= MAX_NUMNODES)
>> diff --git a/mm/mincore.c b/mm/mincore.c
>> index c3f058bd0faf..64c322ed845c 100644
>> --- a/mm/mincore.c
>> +++ b/mm/mincore.c
>> @@ -249,6 +249,8 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len,
>>  	unsigned long pages;
>>  	unsigned char *tmp;
>>  
>> +	start = untagged_addr(start);
>> +
>>  	/* Check the start address: needs to be page-aligned.. */
>>  	if (start & ~PAGE_MASK)
>>  		return -EINVAL;fixup_user_fault
>> diff --git a/mm/mlock.c b/mm/mlock.c
>> index 080f3b36415b..e82609eaa428 100644
>> --- a/mm/mlock.c
>> +++ b/mm/mlock.c
>> @@ -674,6 +674,8 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
>>  	unsigned long lock_limit;
>>  	int error = -ENOMEM;
>>  
>> +	start = untagged_addr(start);
>> +
>>  	if (!can_do_mlock())
>>  		return -EPERM;
>>  
>> @@ -735,6 +737,8 @@ SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
>>  {
>>  	int ret;
>>  
>> +	start = untagged_addr(start);
>> +
>>  	len = PAGE_ALIGN(len + (offset_in_page(start)));
>>  	start &= PAGE_MASK;
>>  
>> diff --git a/mm/mprotect.c b/mm/mprotect.c
>> index bf38dfbbb4b4..19f981b733bc 100644
>> --- a/mm/mprotect.c
>> +++ b/mm/mprotect.c
>> @@ -465,6 +465,8 @@ static int do_mprotect_pkey(unsigned long start, size_t len,
>>  	const bool rier = (current->personality & READ_IMPLIES_EXEC) &&
>>  				(prot & PROT_READ);
>>  
>> +	start = untagged_addr(start);
>> +
>>  	prot &= ~(PROT_GROWSDOWN|PROT_GROWSUP);
>>  	if (grows == (PROT_GROWSDOWN|PROT_GROWSUP)) /* can't be both */
>>  		return -EINVAL;
>> diff --git a/mm/mremap.c b/mm/mremap.c
>> index fc241d23cd97..64c9a3b8be0a 100644
>> --- a/mm/mremap.c
>> +++ b/mm/mremap.c
>> @@ -606,6 +606,13 @@ SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
>>  	LIST_HEAD(uf_unmap_early);
>>  	LIST_HEAD(uf_unmap);
>>  
>> +	/*
>> +	 * Architectures may interpret the tag passed to mmap as a background
>> +	 * colour for the corresponding vma. For mremap we don't allow tagged
>> +	 * new_addr to preserve similar behaviour to mmap.
>> +	 */
>> +	addr = untagged_addr(addr);
>> +
>>  	if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
>>  		return ret;
>>  
>> diff --git a/mm/msync.c b/mm/msync.c
>> index ef30a429623a..c3bd3e75f687 100644
>> --- a/mm/msync.c
>> +++ b/mm/msync.c
>> @@ -37,6 +37,8 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
>>  	int unmapped_error = 0;
>>  	int error = -EINVAL;
>>  
>> +	start = untagged_addr(start);
>> +
>>  	if (flags & ~(MS_ASYNC | MS_INVALIDATE | MS_SYNC))
>>  		goto out;
>>  	if (offset_in_page(start))
>>
> 
>