From: Matthew Wilcox <willy@infradead.org>
To: Christopher Lameter <cl@linux.com>
Cc: Kees Cook <keescook@chromium.org>,
linux-kernel@vger.kernel.org, David Windsor <dave@nullcore.net>,
Pekka Enberg <penberg@kernel.org>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-xfs@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Andy Lutomirski <luto@kernel.org>,
Christoph Hellwig <hch@infradead.org>,
"David S. Miller" <davem@davemloft.net>,
Laura Abbott <labbott@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Christoffer Dall <christoffer.dall@linaro.org>,
Dave Kleikamp <dave.kleikamp@oracle.com>, Jan Kara <jack@suse.cz>,
Luis de Bethencourt <luisbg@kernel.org>,
Marc Zyngier <marc.zyngier@arm.com>,
Rik van Riel <riel@redhat.com>,
Matthew Garrett <mjg59@google.com>,
linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org,
netdev@vger.kernel.org, kernel-hardening@lists.openwall.com
Subject: Re: kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting)
Date: Tue, 16 Jan 2018 09:43:15 -0800 [thread overview]
Message-ID: <20180116174315.GA10461@bombadil.infradead.org> (raw)
In-Reply-To: <alpine.DEB.2.20.1801161049320.5162@nuc-kabylake>
On Tue, Jan 16, 2018 at 10:54:27AM -0600, Christopher Lameter wrote:
> On Tue, 16 Jan 2018, Matthew Wilcox wrote:
>
> > I think that's a good thing! /proc/slabinfo really starts to get grotty
> > above 16 bytes. I'd like to chop off "_cache" from the name of every
> > single slab! If ext4_allocation_context has to become ext4_alloc_ctx,
> > I don't think we're going to lose any valuable information.
>
> Ok so we are going to cut off at 16 charaacters? Sounds good to me.
Excellent!
> > > struct kmem_cache_attr {
> > > char *name;
> > > size_t size;
> > > size_t align;
> > > slab_flags_t flags;
> > > unsigned int useroffset;
> > > unsinged int usersize;
> > > void (*ctor)(void *);
> > > kmem_isolate_func *isolate;
> > > kmem_migrate_func *migrate;
> > > ...
> > > }
> >
> > In these slightly-more-security-conscious days, it's considered poor
> > practice to have function pointers in writable memory. That was why
> > I wanted to make the kmem_cache_attr const.
>
> Sure this data is never changed. It can be const.
It's changed at initialisation. Look:
kmem_cache_create(const char *name, size_t size, size_t align,
slab_flags_t flags, void (*ctor)(void *))
s = create_cache(cache_name, size, size,
calculate_alignment(flags, align, size),
flags, ctor, NULL, NULL);
The 'align' that ends up in s->align, is not the user-specified align.
It's also dependent on runtime information (cache_line_size()), so it
can't be calculated at compile time.
'flags' also gets mangled:
flags &= CACHE_CREATE_MASK;
> I am not married to either way of specifying the sizes. unsigned int would
> be fine with me. SLUB falls back to the page allocator anyways for
> anything above 2* PAGE_SIZE and I think we can do the same for the other
> allocators as well. Zeroing or initializing such a large memory chunk is
> much more expensive than the allocation so it does not make much sense to
> have that directly supported in the slab allocators.
The only slabs larger than 4kB on my system right now are:
kvm_vcpu 0 0 19136 1 8 : tunables 8 4 0 : slabdata 0 0 0
net_namespace 1 1 6080 1 2 : tunables 8 4 0 : slabdata 1 1 0
(other than the fake slabs for kmalloc)
> Some platforms support 64K page size and I could envision a 2M page size
> at some point. So I think we cannot use 16 bits there.
>
> If no one objects then I can use unsigned int there again.
unsigned int would be my preference.
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next prev parent reply other threads:[~2018-01-16 17:43 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-09 20:55 [PATCH v4 00/36] Hardened usercopy whitelisting Kees Cook
2018-01-09 20:55 ` [PATCH 01/36] usercopy: Remove pointer from overflow report Kees Cook
2018-01-09 20:55 ` [PATCH 02/36] usercopy: Include offset in " Kees Cook
2018-01-10 15:25 ` Christopher Lameter
2018-01-10 21:15 ` Kees Cook
2018-01-09 20:55 ` [PATCH 03/36] lkdtm/usercopy: Adjust test to include an offset to check reporting Kees Cook
2018-01-09 20:55 ` [PATCH 04/36] usercopy: Prepare for usercopy whitelisting Kees Cook
2018-01-10 18:28 ` Christopher Lameter
2018-01-10 21:06 ` Kees Cook
2018-01-12 15:10 ` David Laight
2018-01-12 15:56 ` Christopher Lameter
2018-01-14 23:07 ` Matthew Wilcox
2018-01-16 15:21 ` kmem_cache_attr (was Re: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting) Christopher Lameter
2018-01-16 16:05 ` Matthew Wilcox
2018-01-16 16:54 ` Christopher Lameter
2018-01-16 17:43 ` Matthew Wilcox [this message]
2018-01-16 18:07 ` Christopher Lameter
2018-01-16 18:17 ` Christopher Lameter
2018-01-16 21:03 ` Matthew Wilcox
2018-01-17 14:46 ` Christopher Lameter
2018-01-17 17:42 ` Christopher Lameter
2018-01-17 19:31 ` Matthew Wilcox
2018-01-20 1:58 ` Christopher Lameter
2018-01-09 20:55 ` [PATCH 05/36] usercopy: WARN() on slab cache usercopy region violations Kees Cook
2018-01-10 18:31 ` Christopher Lameter
2018-01-10 20:14 ` Kees Cook
2018-01-09 20:55 ` [PATCH 06/36] usercopy: Mark kmalloc caches as usercopy caches Kees Cook
2018-01-09 20:55 ` [PATCH 07/36] dcache: Define usercopy region in dentry_cache slab cache Kees Cook
2018-01-09 20:55 ` [PATCH 08/36] vfs: Define usercopy region in names_cache slab caches Kees Cook
2018-01-09 20:55 ` [PATCH 09/36] vfs: Copy struct mount.mnt_id to userspace using put_user() Kees Cook
2018-01-09 20:55 ` [PATCH 10/36] ext4: Define usercopy region in ext4_inode_cache slab cache Kees Cook
2018-01-09 20:55 ` [PATCH 11/36] ext2: Define usercopy region in ext2_inode_cache " Kees Cook
2018-01-09 20:55 ` [PATCH 12/36] jfs: Define usercopy region in jfs_ip " Kees Cook
2018-01-09 20:55 ` [PATCH 13/36] befs: Define usercopy region in befs_inode_cache " Kees Cook
2018-01-10 10:53 ` Luis de Bethencourt
2018-01-09 20:55 ` [PATCH 14/36] exofs: Define usercopy region in exofs_inode_cache " Kees Cook
2018-01-09 20:55 ` [PATCH 15/36] orangefs: Define usercopy region in orangefs_inode_cache " Kees Cook
2018-01-09 20:55 ` [PATCH 16/36] ufs: Define usercopy region in ufs_inode_cache " Kees Cook
2018-01-09 20:55 ` [PATCH 17/36] vxfs: Define usercopy region in vxfs_inode " Kees Cook
2018-01-09 20:55 ` [PATCH 18/36] cifs: Define usercopy region in cifs_request " Kees Cook
2018-01-09 20:55 ` [PATCH 19/36] scsi: Define usercopy region in scsi_sense_cache " Kees Cook
2018-01-09 20:55 ` [PATCH 20/36] net: Define usercopy region in struct proto " Kees Cook
2018-01-09 20:55 ` [PATCH 21/36] ip: Define usercopy region in IP " Kees Cook
2018-01-09 20:55 ` [PATCH 22/36] caif: Define usercopy region in caif " Kees Cook
2018-01-09 20:55 ` [PATCH 23/36] sctp: Define usercopy region in SCTP " Kees Cook
2018-01-09 20:55 ` [PATCH 24/36] sctp: Copy struct sctp_sock.autoclose to userspace using put_user() Kees Cook
2018-01-09 20:55 ` [PATCH 25/36] net: Restrict unwhitelisted proto caches to size 0 Kees Cook
2018-01-09 20:55 ` [PATCH 26/36] fork: Define usercopy region in mm_struct slab caches Kees Cook
2018-01-09 20:55 ` [PATCH 27/36] fork: Define usercopy region in thread_stack " Kees Cook
2018-01-09 20:55 ` [PATCH 28/36] fork: Provide usercopy whitelisting for task_struct Kees Cook
2018-01-09 20:55 ` [PATCH 29/36] x86: Implement thread_struct whitelist for hardened usercopy Kees Cook
2018-01-09 20:55 ` [PATCH 30/36] arm64: " Kees Cook
2018-01-09 20:56 ` [PATCH 31/36] arm: " Kees Cook
2018-01-09 20:56 ` [PATCH 32/36] kvm: whitelist struct kvm_vcpu_arch Kees Cook
2018-01-09 20:56 ` [PATCH 33/36] kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl Kees Cook
2018-01-09 20:56 ` [PATCH 34/36] usercopy: Allow strict enforcement of whitelists Kees Cook
2018-01-09 20:56 ` [PATCH 35/36] usercopy: Restrict non-usercopy caches to size 0 Kees Cook
2018-01-09 20:56 ` [PATCH 36/36] lkdtm: Update usercopy tests for whitelisting Kees Cook
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