From e5733d8c89c3b57c8fcd40b8acf508388fabaa42 Mon Sep 17 00:00:00 2001 From: Reinette Chatre Date: Wed, 2 Feb 2022 11:41:12 -0800 Subject: [PATCH 1/2] x86/sgx: Fix missing poison handling in reclaimer The SGX reclaimer code lacks page poison handling in its main free path. This can lead to avoidable machine checks if a poisoned page is freed and reallocated instead of being isolated. A troublesome scenario is: 1. Machine check (#MC) occurs (asynchronous, !MF_ACTION_REQUIRED) 2. arch_memory_failure() is eventually called 3. (SGX) page->poison set to 1 4. Page is reclaimed 5. Page added to normal free lists by sgx_reclaim_pages() ^ This is the bug (poison pages should be isolated on the sgx_poison_page_list instead) 6. Page is reallocated by some innocent enclave, a second (synchronous) in-kernel #MC is induced, probably during EADD instruction. ^ This is the fallout from the bug (6) is unfortunate and can be avoided by replacing the open coded enclave page freeing code in the reclaimer with sgx_free_epc_page() to obtain support for poison page handling that includes placing the poisoned page on the correct list. Fixes: d6d261bded8a ("x86/sgx: Add new sgx_epc_page flag bit to mark free pages") Fixes: 992801ae9243 ("x86/sgx: Initial poison handling for dirty and free pages") Signed-off-by: Reinette Chatre Signed-off-by: Dave Hansen Reviewed-by: Jarkko Sakkinen Link: https://lkml.kernel.org/r/dcc95eb2aaefb042527ac50d0a50738c7c160dac.1643830353.git.reinette.chatre@intel.com --- arch/x86/kernel/cpu/sgx/main.c | 10 +--------- 1 file changed, 1 insertion(+), 9 deletions(-) diff --git a/arch/x86/kernel/cpu/sgx/main.c b/arch/x86/kernel/cpu/sgx/main.c index 4b41efc9e367..8e4bc6453d26 100644 --- a/arch/x86/kernel/cpu/sgx/main.c +++ b/arch/x86/kernel/cpu/sgx/main.c @@ -344,10 +344,8 @@ static void sgx_reclaim_pages(void) { struct sgx_epc_page *chunk[SGX_NR_TO_SCAN]; struct sgx_backing backing[SGX_NR_TO_SCAN]; - struct sgx_epc_section *section; struct sgx_encl_page *encl_page; struct sgx_epc_page *epc_page; - struct sgx_numa_node *node; pgoff_t page_index; int cnt = 0; int ret; @@ -418,13 +416,7 @@ skip: kref_put(&encl_page->encl->refcount, sgx_encl_release); epc_page->flags &= ~SGX_EPC_PAGE_RECLAIMER_TRACKED; - section = &sgx_epc_sections[epc_page->section]; - node = section->node; - - spin_lock(&node->lock); - list_add_tail(&epc_page->list, &node->free_page_list); - spin_unlock(&node->lock); - atomic_long_inc(&sgx_nr_free_pages); + sgx_free_epc_page(epc_page); } } From 44cad52cc14ae10062f142ec16ede489bccf4469 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 14 Feb 2022 13:05:49 +0100 Subject: [PATCH 2/2] x86/ptrace: Fix xfpregs_set()'s incorrect xmm clearing MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit xfpregs_set() handles 32-bit REGSET_XFP and 64-bit REGSET_FP. The actual code treats these regsets as modern FX state (i.e. the beginning part of XSTATE). The declarations of the regsets thought they were the legacy i387 format. The code thought they were the 32-bit (no xmm8..15) variant of XSTATE and, for good measure, made the high bits disappear by zeroing the wrong part of the buffer. The latter broke ptrace, and everything else confused anyone trying to understand the code. In particular, the nonsense definitions of the regsets confused me when I wrote this code. Clean this all up. Change the declarations to match reality (which shouldn't change the generated code, let alone the ABI) and fix xfpregs_set() to clear the correct bits and to only do so for 32-bit callers. Fixes: 6164331d15f7 ("x86/fpu: Rewrite xfpregs_set()") Reported-by: Luís Ferreira Signed-off-by: Andy Lutomirski Signed-off-by: Borislav Petkov Cc: Link: https://bugzilla.kernel.org/show_bug.cgi?id=215524 Link: https://lore.kernel.org/r/YgpFnZpF01WwR8wU@zn.tnic --- arch/x86/kernel/fpu/regset.c | 9 ++++----- arch/x86/kernel/ptrace.c | 4 ++-- 2 files changed, 6 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 437d7c930c0b..75ffaef8c299 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -91,11 +91,9 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, const void *kbuf, const void __user *ubuf) { struct fpu *fpu = &target->thread.fpu; - struct user32_fxsr_struct newstate; + struct fxregs_state newstate; int ret; - BUILD_BUG_ON(sizeof(newstate) != sizeof(struct fxregs_state)); - if (!cpu_feature_enabled(X86_FEATURE_FXSR)) return -ENODEV; @@ -116,9 +114,10 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, /* Copy the state */ memcpy(&fpu->fpstate->regs.fxsave, &newstate, sizeof(newstate)); - /* Clear xmm8..15 */ + /* Clear xmm8..15 for 32-bit callers */ BUILD_BUG_ON(sizeof(fpu->__fpstate.regs.fxsave.xmm_space) != 16 * 16); - memset(&fpu->fpstate->regs.fxsave.xmm_space[8], 0, 8 * 16); + if (in_ia32_syscall()) + memset(&fpu->fpstate->regs.fxsave.xmm_space[8*4], 0, 8 * 16); /* Mark FP and SSE as in use when XSAVE is enabled */ if (use_xsave()) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 6d2244c94799..8d2f2f995539 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -1224,7 +1224,7 @@ static struct user_regset x86_64_regsets[] __ro_after_init = { }, [REGSET_FP] = { .core_note_type = NT_PRFPREG, - .n = sizeof(struct user_i387_struct) / sizeof(long), + .n = sizeof(struct fxregs_state) / sizeof(long), .size = sizeof(long), .align = sizeof(long), .active = regset_xregset_fpregs_active, .regset_get = xfpregs_get, .set = xfpregs_set }, @@ -1271,7 +1271,7 @@ static struct user_regset x86_32_regsets[] __ro_after_init = { }, [REGSET_XFP] = { .core_note_type = NT_PRXFPREG, - .n = sizeof(struct user32_fxsr_struct) / sizeof(u32), + .n = sizeof(struct fxregs_state) / sizeof(u32), .size = sizeof(u32), .align = sizeof(u32), .active = regset_xregset_fpregs_active, .regset_get = xfpregs_get, .set = xfpregs_set },