Date: Tue, 9 Jan 2018 12:55:29 -0800 From: Kees Cook <keescook@...omium.org> To: linux-kernel@...r.kernel.org Cc: Kees Cook <keescook@...omium.org>, Linus Torvalds <torvalds@...ux-foundation.org>, David Windsor <dave@...lcore.net>, Alexander Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Andy Lutomirski <luto@...nel.org>, Christoph Hellwig <hch@...radead.org>, Christoph Lameter <cl@...ux.com>, "David S. Miller" <davem@...emloft.net>, Laura Abbott <labbott@...hat.com>, Mark Rutland <mark.rutland@....com>, "Martin K. Petersen" <martin.petersen@...cle.com>, Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ibm.com>, Christoffer Dall <christoffer.dall@...aro.org>, Dave Kleikamp <dave.kleikamp@...cle.com>, Jan Kara <jack@...e.cz>, Luis de Bethencourt <luisbg@...nel.org>, Marc Zyngier <marc.zyngier@....com>, Rik van Riel <riel@...hat.com>, Matthew Garrett <mjg59@...gle.com>, linux-fsdevel@...r.kernel.org, linux-arch@...r.kernel.org, netdev@...r.kernel.org, linux-mm@...ck.org, kernel-hardening@...ts.openwall.com Subject: [PATCH v4 00/36] Hardened usercopy whitelisting v4: - refactor reporting to include offset and remove %p - explicitly WARN by default for the whitelisting - add KVM whitelists and harden ioctl handling v3: - added LKDTM update patch - downgrade BUGs to WARNs and fail closed - add Acks/Reviews from v2 v2: - added tracing of allocation and usage - refactored solutions for task_struct - split up network patches for readability I intend for this to land via my usercopy hardening tree, so Acks, Reviewed, and Tested-bys would be greatly appreciated. FWIW, the bulk of this series has survived for months in 0-day testing and -next, with the more recently-added offset-reporting having existed there for a week. Linus, getting your attention early on this -- instead of during the merge window :) -- would be greatly appreciated. I'm hoping this is a good time, in a slight lull in PTI and related things needing attention. ---- This series is modified from Brad Spengler/PaX Team's PAX_USERCOPY code in the last public patch of grsecurity/PaX based on our understanding of the code. Changes or omissions from the original code are ours and don't reflect the original grsecurity/PaX code. David Windsor did the bulk of the porting, refactoring, splitting, testing, etc; I did some extra tweaks, hunk moving, traces, and extra patches. Description from patch 1: Currently, hardened usercopy performs dynamic bounds checking on slab cache objects. This is good, but still leaves a lot of kernel memory available to be copied to/from userspace in the face of bugs. To further restrict what memory is available for copying, this creates a way to whitelist specific areas of a given slab cache object for copying to/from userspace, allowing much finer granularity of access control. Slab caches that are never exposed to userspace can declare no whitelist for their objects, thereby keeping them unavailable to userspace via dynamic copy operations. (Note, an implicit form of whitelisting is the use of constant sizes in usercopy operations and get_user()/put_user(); these bypass hardened usercopy checks since these sizes cannot change at runtime.) To support this whitelist annotation, usercopy region offset and size members are added to struct kmem_cache. The slab allocator receives a new function, kmem_cache_create_usercopy(), that creates a new cache with a usercopy region defined, suitable for declaring spans of fields within the objects that get copied to/from userspace. In this patch, the default kmem_cache_create() marks the entire allocation as whitelisted, leaving it semantically unchanged. Once all fine-grained whitelists have been added (in subsequent patches), this will be changed to a usersize of 0, making caches created with kmem_cache_create() not copyable to/from userspace. After the entire usercopy whitelist series is applied, less than 15% of the slab cache memory remains exposed to potential usercopy bugs after a fresh boot: Total Slab Memory: 48074720 Usercopyable Memory: 6367532 13.2% task_struct 0.2% 4480/1630720 RAW 0.3% 300/96000 RAWv6 2.1% 1408/64768 ext4_inode_cache 3.0% 269760/8740224 dentry 11.1% 585984/5273856 mm_struct 29.1% 54912/188448 kmalloc-8 100.0% 24576/24576 kmalloc-16 100.0% 28672/28672 kmalloc-32 100.0% 81920/81920 kmalloc-192 100.0% 96768/96768 kmalloc-128 100.0% 143360/143360 names_cache 100.0% 163840/163840 kmalloc-64 100.0% 167936/167936 kmalloc-256 100.0% 339968/339968 kmalloc-512 100.0% 350720/350720 kmalloc-96 100.0% 455616/455616 kmalloc-8192 100.0% 655360/655360 kmalloc-1024 100.0% 812032/812032 kmalloc-4096 100.0% 819200/819200 kmalloc-2048 100.0% 1310720/1310720 After some kernel build workloads, the percentage (mainly driven by dentry and inode caches expanding) drops under 10%: Total Slab Memory: 95516184 Usercopyable Memory: 8497452 8.8% task_struct 0.2% 4000/1456000 RAW 0.3% 300/96000 RAWv6 2.1% 1408/64768 ext4_inode_cache 3.0% 1217280/39439872 dentry 11.1% 1623200/14608800 mm_struct 29.1% 73216/251264 kmalloc-8 100.0% 24576/24576 kmalloc-16 100.0% 28672/28672 kmalloc-32 100.0% 94208/94208 kmalloc-192 100.0% 96768/96768 kmalloc-128 100.0% 143360/143360 names_cache 100.0% 163840/163840 kmalloc-64 100.0% 245760/245760 kmalloc-256 100.0% 339968/339968 kmalloc-512 100.0% 350720/350720 kmalloc-96 100.0% 563520/563520 kmalloc-8192 100.0% 655360/655360 kmalloc-1024 100.0% 794624/794624 kmalloc-4096 100.0% 819200/819200 kmalloc-2048 100.0% 1257472/1257472 ------ The patches are broken in several stages of changes: Report offsets and drop %p usage: [PATCH 01/36] usercopy: Remove pointer from overflow report [PATCH 02/36] usercopy: Include offset in overflow report [PATCH 03/36] lkdtm/usercopy: Adjust test to include an offset to Prepare and whitelist kmalloc: [PATCH 04/36] usercopy: Prepare for usercopy whitelisting [PATCH 05/36] usercopy: WARN() on slab cache usercopy region [PATCH 06/36] usercopy: Mark kmalloc caches as usercopy caches Update VFS layer for symlinks and other inline storage: [PATCH 07/36] dcache: Define usercopy region in dentry_cache slab [PATCH 08/36] vfs: Define usercopy region in names_cache slab caches [PATCH 09/36] vfs: Copy struct mount.mnt_id to userspace using [PATCH 10/36] ext4: Define usercopy region in ext4_inode_cache slab [PATCH 11/36] ext2: Define usercopy region in ext2_inode_cache slab [PATCH 12/36] jfs: Define usercopy region in jfs_ip slab cache [PATCH 13/36] befs: Define usercopy region in befs_inode_cache slab [PATCH 14/36] exofs: Define usercopy region in exofs_inode_cache slab [PATCH 15/36] orangefs: Define usercopy region in [PATCH 16/36] ufs: Define usercopy region in ufs_inode_cache slab [PATCH 17/36] vxfs: Define usercopy region in vxfs_inode slab cache [PATCH 18/36] cifs: Define usercopy region in cifs_request slab cache Update scsi layer for inline storage: [PATCH 19/36] scsi: Define usercopy region in scsi_sense_cache slab Whitelist a few network protocol-specific areas of memory: [PATCH 20/36] net: Define usercopy region in struct proto slab cache [PATCH 21/36] ip: Define usercopy region in IP proto slab cache [PATCH 22/36] caif: Define usercopy region in caif proto slab cache [PATCH 23/36] sctp: Define usercopy region in SCTP proto slab cache [PATCH 24/36] sctp: Copy struct sctp_sock.autoclose to userspace [PATCH 25/36] net: Restrict unwhitelisted proto caches to size 0 Whitelist areas of process memory: [PATCH 26/36] fork: Define usercopy region in mm_struct slab caches [PATCH 27/36] fork: Define usercopy region in thread_stack slab Deal with per-architecture thread_struct whitelisting: [PATCH 28/36] fork: Provide usercopy whitelisting for task_struct [PATCH 29/36] x86: Implement thread_struct whitelist for hardened [PATCH 30/36] arm64: Implement thread_struct whitelist for hardened [PATCH 31/36] arm: Implement thread_struct whitelist for hardened Update KVM for whitelisting: [PATCH 32/36] kvm: whitelist struct kvm_vcpu_arch [PATCH 33/36] kvm: x86: fix KVM_XEN_HVM_CONFIG ioctl Make blacklisting the default, with optional fail-closed: [PATCH 34/36] usercopy: Allow strict enforcement of whitelists [PATCH 35/36] usercopy: Restrict non-usercopy caches to size 0 Update LKDTM: [PATCH 36/36] lkdtm: Update usercopy tests for whitelisting Thanks! -Kees (and David)
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