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Andrew Zaborowski dc5de5bd6d x86/sgx: Prevent attempts to reclaim poisoned pages 
[ Upstream commit ed16618c38 ]

TL;DR: SGX page reclaim touches the page to copy its contents to
secondary storage. SGX instructions do not gracefully handle machine
checks. Despite this, the existing SGX code will try to reclaim pages
that it _knows_ are poisoned. Avoid even trying to reclaim poisoned pages.

The longer story:

Pages used by an enclave only get epc_page->poison set in
arch_memory_failure() but they currently stay on sgx_active_page_list until
sgx_encl_release(), with the SGX_EPC_PAGE_RECLAIMER_TRACKED flag untouched.

epc_page->poison is not checked in the reclaimer logic meaning that, if other
conditions are met, an attempt will be made to reclaim an EPC page that was
poisoned.  This is bad because 1. we don't want that page to end up added
to another enclave and 2. it is likely to cause one core to shut down
and the kernel to panic.

Specifically, reclaiming uses microcode operations including "EWB" which
accesses the EPC page contents to encrypt and write them out to non-SGX
memory.  Those operations cannot handle MCEs in their accesses other than
by putting the executing core into a special shutdown state (affecting
both threads with HT.)  The kernel will subsequently panic on the
remaining cores seeing the core didn't enter MCE handler(s) in time.

Call sgx_unmark_page_reclaimable() to remove the affected EPC page from
sgx_active_page_list on memory error to stop it being considered for
reclaiming.

Testing epc_page->poison in sgx_reclaim_pages() would also work but I assume
it's better to add code in the less likely paths.

The affected EPC page is not added to &node->sgx_poison_page_list until
later in sgx_encl_release()->sgx_free_epc_page() when it is EREMOVEd.
Membership on other lists doesn't change to avoid changing any of the
lists' semantics except for sgx_active_page_list.  There's a "TBD" comment
in arch_memory_failure() about pre-emptive actions, the goal here is not
to address everything that it may imply.

This also doesn't completely close the time window when a memory error
notification will be fatal (for a not previously poisoned EPC page) --
the MCE can happen after sgx_reclaim_pages() has selected its candidates
or even *inside* a microcode operation (actually easy to trigger due to
the amount of time spent in them.)

The spinlock in sgx_unmark_page_reclaimable() is safe because
memory_failure() runs in process context and no spinlocks are held,
explicitly noted in a mm/memory-failure.c comment.

Signed-off-by: Andrew Zaborowski <andrew.zaborowski@intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: balrogg@gmail.com
Cc: linux-sgx@vger.kernel.org
Link: https://lore.kernel.org/r/20250508230429.456271-1-andrew.zaborowski@intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2025-06-27 11:11:30 +01:00
arch x86/sgx: Prevent attempts to reclaim poisoned pages 2025-06-27 11:11:30 +01:00
block block: Clear BIO_EMULATES_ZONE_APPEND flag on BIO completion 2025-06-27 11:11:19 +01:00
certs sign-file,extract-cert: use pkcs11 provider for OPENSSL MAJOR >= 3 2024-09-20 19:52:48 +03:00
crypto crypto: api - Redo lookup on EEXIST 2025-06-19 15:31:30 +02:00
Documentation regulator: dt-bindings: mt6357: Drop fixed compatible requirement 2025-06-19 15:32:37 +02:00
drivers wifi: rtw89: leave idle mode when setting WEP encryption for AP mode 2025-06-27 11:11:30 +01:00
fs f2fs: use vmalloc instead of kvmalloc in .init_{,de}compress_ctx 2025-06-27 11:11:28 +01:00
include tcp: add receive queue awareness in tcp_rcv_space_adjust() 2025-06-27 11:11:30 +01:00
init rust: clean Rust 1.88.0's unnecessary_transmutes lint 2025-05-18 08:24:51 +02:00
io_uring io_uring/kbuf: account ring io_buffer_list memory 2025-06-27 11:11:14 +01:00
ipc ipc: fix to protect IPCS lookups using RCU 2025-06-27 11:11:22 +01:00
kernel bpf: Check rcu_read_lock_trace_held() in bpf_map_lookup_percpu_elem() 2025-06-27 11:11:28 +01:00
lib iov_iter: use iov_offset for length calculation in iov_iter_aligned_bvec 2025-06-19 15:32:21 +02:00
LICENSES LICENSES: add 0BSD license text 2024-09-01 20:43:24 -07:00
mm mm/hugetlb: fix huge_pmd_unshare() vs GUP-fast race 2025-06-27 11:11:26 +01:00
net tcp: add receive queue awareness in tcp_rcv_space_adjust() 2025-06-27 11:11:30 +01:00
rust rust: alloc: add missing invariant in Vec::set_len() 2025-06-19 15:32:09 +02:00
samples samples/bpf: Fix compilation failure for samples/bpf on LoongArch Fedora 2025-05-29 11:02:01 +02:00
scripts Make 'cc-option' work correctly for the -Wno-xyzzy pattern 2025-06-27 11:11:27 +01:00
security smack: Revert "smackfs: Added check catlen" 2025-05-29 11:02:48 +02:00
sound ASoC: tegra210_ahub: Add check to of_device_get_match_data() 2025-06-27 11:11:27 +01:00
tools libbpf/btf: Fix string handling to support multi-split BTF 2025-06-27 11:11:29 +01:00
usr kbuild: hdrcheck: fix cross build with clang 2025-03-13 13:02:18 +01:00
virt KVM: Add member to struct kvm_gfn_range to indicate private/shared 2025-05-22 14:29:36 +02:00
.clang-format clang-format: Update with v6.11-rc1's for_each macro list 2024-08-02 13:20:31 +02:00
.clippy.toml rust: clean Rust 1.88.0's warning about clippy::disallowed_macros configuration 2025-05-18 08:24:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.editorconfig .editorconfig: remove trim_trailing_whitespace option 2024-06-13 16:47:52 +02:00
.get_maintainer.ignore Add Jeff Kirsher to .get_maintainer.ignore 2024-03-08 11:36:54 +00:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore rust: introduce .clippy.toml 2025-03-13 13:01:42 +01:00
.mailmap mailmap: add entry for Thorsten Blum 2024-11-07 14:14:59 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Remove self from DSA entry 2024-11-03 12:52:38 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS MAINTAINERS: Update Alexey Makhalov's email address 2025-05-22 14:29:46 +02:00
Makefile Linux 6.12.34 2025-06-19 15:32:38 +02:00
README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.