From e34dbbc85d64af59176fe59fad7b4122f4330fe2 Mon Sep 17 00:00:00 2001 From: "Xin Li (Intel)" Date: Mon, 9 Jun 2025 01:40:53 -0700 Subject: [PATCH 1/8] x86/fred/signal: Prevent immediate repeat of single step trap on return from SIGTRAP handler Clear the software event flag in the augmented SS to prevent immediate repeat of single step trap on return from SIGTRAP handler if the trap flag (TF) is set without an external debugger attached. Following is a typical single-stepping flow for a user process: 1) The user process is prepared for single-stepping by setting RFLAGS.TF = 1. 2) When any instruction in user space completes, a #DB is triggered. 3) The kernel handles the #DB and returns to user space, invoking the SIGTRAP handler with RFLAGS.TF = 0. 4) After the SIGTRAP handler finishes, the user process performs a sigreturn syscall, restoring the original state, including RFLAGS.TF = 1. 5) Goto step 2. According to the FRED specification: A) Bit 17 in the augmented SS is designated as the software event flag, which is set to 1 for FRED event delivery of SYSCALL, SYSENTER, or INT n. B) If bit 17 of the augmented SS is 1 and ERETU would result in RFLAGS.TF = 1, a single-step trap will be pending upon completion of ERETU. In step 4) above, the software event flag is set upon the sigreturn syscall, and its corresponding ERETU would restore RFLAGS.TF = 1. This combination causes a pending single-step trap upon completion of ERETU. Therefore, another #DB is triggered before any user space instruction is executed, which leads to an infinite loop in which the SIGTRAP handler keeps being invoked on the same user space IP. Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code") Suggested-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li (Intel) Signed-off-by: Dave Hansen Tested-by: Sohil Mehta Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/20250609084054.2083189-2-xin%40zytor.com --- arch/x86/include/asm/sighandling.h | 22 ++++++++++++++++++++++ arch/x86/kernel/signal_32.c | 4 ++++ arch/x86/kernel/signal_64.c | 4 ++++ 3 files changed, 30 insertions(+) diff --git a/arch/x86/include/asm/sighandling.h b/arch/x86/include/asm/sighandling.h index e770c4fc47f4..8727c7e21dd1 100644 --- a/arch/x86/include/asm/sighandling.h +++ b/arch/x86/include/asm/sighandling.h @@ -24,4 +24,26 @@ int ia32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs); int x64_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs); int x32_setup_rt_frame(struct ksignal *ksig, struct pt_regs *regs); +/* + * To prevent immediate repeat of single step trap on return from SIGTRAP + * handler if the trap flag (TF) is set without an external debugger attached, + * clear the software event flag in the augmented SS, ensuring no single-step + * trap is pending upon ERETU completion. + * + * Note, this function should be called in sigreturn() before the original + * state is restored to make sure the TF is read from the entry frame. + */ +static __always_inline void prevent_single_step_upon_eretu(struct pt_regs *regs) +{ + /* + * If the trap flag (TF) is set, i.e., the sigreturn() SYSCALL instruction + * is being single-stepped, do not clear the software event flag in the + * augmented SS, thus a debugger won't skip over the following instruction. + */ +#ifdef CONFIG_X86_FRED + if (!(regs->flags & X86_EFLAGS_TF)) + regs->fred_ss.swevent = 0; +#endif +} + #endif /* _ASM_X86_SIGHANDLING_H */ diff --git a/arch/x86/kernel/signal_32.c b/arch/x86/kernel/signal_32.c index 98123ff10506..42bbc42bd350 100644 --- a/arch/x86/kernel/signal_32.c +++ b/arch/x86/kernel/signal_32.c @@ -152,6 +152,8 @@ SYSCALL32_DEFINE0(sigreturn) struct sigframe_ia32 __user *frame = (struct sigframe_ia32 __user *)(regs->sp-8); sigset_t set; + prevent_single_step_upon_eretu(regs); + if (!access_ok(frame, sizeof(*frame))) goto badframe; if (__get_user(set.sig[0], &frame->sc.oldmask) @@ -175,6 +177,8 @@ SYSCALL32_DEFINE0(rt_sigreturn) struct rt_sigframe_ia32 __user *frame; sigset_t set; + prevent_single_step_upon_eretu(regs); + frame = (struct rt_sigframe_ia32 __user *)(regs->sp - 4); if (!access_ok(frame, sizeof(*frame))) diff --git a/arch/x86/kernel/signal_64.c b/arch/x86/kernel/signal_64.c index ee9453891901..d483b585c6c6 100644 --- a/arch/x86/kernel/signal_64.c +++ b/arch/x86/kernel/signal_64.c @@ -250,6 +250,8 @@ SYSCALL_DEFINE0(rt_sigreturn) sigset_t set; unsigned long uc_flags; + prevent_single_step_upon_eretu(regs); + frame = (struct rt_sigframe __user *)(regs->sp - sizeof(long)); if (!access_ok(frame, sizeof(*frame))) goto badframe; @@ -366,6 +368,8 @@ COMPAT_SYSCALL_DEFINE0(x32_rt_sigreturn) sigset_t set; unsigned long uc_flags; + prevent_single_step_upon_eretu(regs); + frame = (struct rt_sigframe_x32 __user *)(regs->sp - 8); if (!access_ok(frame, sizeof(*frame))) From f287822688eeb44ae1cf6ac45701d965efc33218 Mon Sep 17 00:00:00 2001 From: "Xin Li (Intel)" Date: Mon, 9 Jun 2025 01:40:54 -0700 Subject: [PATCH 2/8] selftests/x86: Add a test to detect infinite SIGTRAP handler loop MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit When FRED is enabled, if the Trap Flag (TF) is set without an external debugger attached, it can lead to an infinite loop in the SIGTRAP handler. To avoid this, the software event flag in the augmented SS must be cleared, ensuring that no single-step trap remains pending when ERETU completes. This test checks for that specific scenario—verifying whether the kernel correctly prevents an infinite SIGTRAP loop in this edge case when FRED is enabled. The test should _always_ pass with IDT event delivery, thus no need to disable the test even when FRED is not enabled. Signed-off-by: Xin Li (Intel) Signed-off-by: Dave Hansen Tested-by: Sohil Mehta Cc:stable@vger.kernel.org Link: https://lore.kernel.org/all/20250609084054.2083189-3-xin%40zytor.com --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/sigtrap_loop.c | 101 +++++++++++++++++++++ 2 files changed, 102 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/x86/sigtrap_loop.c diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index f703fcfe9f7c..83148875a12c 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -12,7 +12,7 @@ CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh "$(CC)" trivial_program.c -no-pie) TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \ check_initial_reg_state sigreturn iopl ioperm \ - test_vsyscall mov_ss_trap \ + test_vsyscall mov_ss_trap sigtrap_loop \ syscall_arg_fault fsgsbase_restore sigaltstack TARGETS_C_BOTHBITS += nx_stack TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \ diff --git a/tools/testing/selftests/x86/sigtrap_loop.c b/tools/testing/selftests/x86/sigtrap_loop.c new file mode 100644 index 000000000000..9d065479e89f --- /dev/null +++ b/tools/testing/selftests/x86/sigtrap_loop.c @@ -0,0 +1,101 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2025 Intel Corporation + */ +#define _GNU_SOURCE + +#include +#include +#include +#include +#include +#include + +#ifdef __x86_64__ +# define REG_IP REG_RIP +#else +# define REG_IP REG_EIP +#endif + +static void sethandler(int sig, void (*handler)(int, siginfo_t *, void *), int flags) +{ + struct sigaction sa; + + memset(&sa, 0, sizeof(sa)); + sa.sa_sigaction = handler; + sa.sa_flags = SA_SIGINFO | flags; + sigemptyset(&sa.sa_mask); + + if (sigaction(sig, &sa, 0)) + err(1, "sigaction"); + + return; +} + +static void sigtrap(int sig, siginfo_t *info, void *ctx_void) +{ + ucontext_t *ctx = (ucontext_t *)ctx_void; + static unsigned int loop_count_on_same_ip; + static unsigned long last_trap_ip; + + if (last_trap_ip == ctx->uc_mcontext.gregs[REG_IP]) { + printf("\tTrapped at %016lx\n", last_trap_ip); + + /* + * If the same IP is hit more than 10 times in a row, it is + * _considered_ an infinite loop. + */ + if (++loop_count_on_same_ip > 10) { + printf("[FAIL]\tDetected SIGTRAP infinite loop\n"); + exit(1); + } + + return; + } + + loop_count_on_same_ip = 0; + last_trap_ip = ctx->uc_mcontext.gregs[REG_IP]; + printf("\tTrapped at %016lx\n", last_trap_ip); +} + +int main(int argc, char *argv[]) +{ + sethandler(SIGTRAP, sigtrap, 0); + + /* + * Set the Trap Flag (TF) to single-step the test code, therefore to + * trigger a SIGTRAP signal after each instruction until the TF is + * cleared. + * + * Because the arithmetic flags are not significant here, the TF is + * set by pushing 0x302 onto the stack and then popping it into the + * flags register. + * + * Four instructions in the following asm code are executed with the + * TF set, thus the SIGTRAP handler is expected to run four times. + */ + printf("[RUN]\tSIGTRAP infinite loop detection\n"); + asm volatile( +#ifdef __x86_64__ + /* + * Avoid clobbering the redzone + * + * Equivalent to "sub $128, %rsp", however -128 can be encoded + * in a single byte immediate while 128 uses 4 bytes. + */ + "add $-128, %rsp\n\t" +#endif + "push $0x302\n\t" + "popf\n\t" + "nop\n\t" + "nop\n\t" + "push $0x202\n\t" + "popf\n\t" +#ifdef __x86_64__ + "sub $-128, %rsp\n\t" +#endif + ); + + printf("[OK]\tNo SIGTRAP infinite loop detected\n"); + return 0; +} From 0b3bc018e86afdc0cbfef61328c63d5c08f8b370 Mon Sep 17 00:00:00 2001 From: Kai Huang Date: Sat, 7 Jun 2025 01:07:37 +1200 Subject: [PATCH 3/8] x86/virt/tdx: Avoid indirect calls to TDX assembly functions Two 'static inline' TDX helper functions (sc_retry() and sc_retry_prerr()) take function pointer arguments which refer to assembly functions. Normally, the compiler inlines the TDX helper, realizes that the function pointer targets are completely static -- thus can be resolved at compile time -- and generates direct call instructions. But, other times (like when CONFIG_CC_OPTIMIZE_FOR_SIZE=y), the compiler declines to inline the helpers and will instead generate indirect call instructions. Indirect calls to assembly functions require special annotation (for various Control Flow Integrity mechanisms). But TDX assembly functions lack the special annotations and can only be called directly. Annotate both the helpers as '__always_inline' to prod the compiler into maintaining the direct calls. There is no guarantee here, but Peter has volunteered to report the compiler bug if this assumption ever breaks[1]. Fixes: 1e66a7e27539 ("x86/virt/tdx: Handle SEAMCALL no entropy error in common code") Fixes: df01f5ae07dd ("x86/virt/tdx: Add SEAMCALL error printing for module initialization") Signed-off-by: Kai Huang Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/lkml/20250605145914.GW39944@noisy.programming.kicks-ass.net/ [1] Link: https://lore.kernel.org/all/20250606130737.30713-1-kai.huang%40intel.com --- arch/x86/include/asm/tdx.h | 2 +- arch/x86/virt/vmx/tdx/tdx.c | 5 +++-- 2 files changed, 4 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index 8b19294600c4..7ddef3a69866 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -106,7 +106,7 @@ void tdx_init(void); typedef u64 (*sc_func_t)(u64 fn, struct tdx_module_args *args); -static inline u64 sc_retry(sc_func_t func, u64 fn, +static __always_inline u64 sc_retry(sc_func_t func, u64 fn, struct tdx_module_args *args) { int retry = RDRAND_RETRY_LOOPS; diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c index 2457d13c3f9e..c7a9a087ccaf 100644 --- a/arch/x86/virt/vmx/tdx/tdx.c +++ b/arch/x86/virt/vmx/tdx/tdx.c @@ -75,8 +75,9 @@ static inline void seamcall_err_ret(u64 fn, u64 err, args->r9, args->r10, args->r11); } -static inline int sc_retry_prerr(sc_func_t func, sc_err_func_t err_func, - u64 fn, struct tdx_module_args *args) +static __always_inline int sc_retry_prerr(sc_func_t func, + sc_err_func_t err_func, + u64 fn, struct tdx_module_args *args) { u64 sret = sc_retry(func, fn, args); From 1dbf30fdb5e57fb2c39f17f35f2b544d5de34397 Mon Sep 17 00:00:00 2001 From: Juergen Gross Date: Tue, 3 Jun 2025 14:14:41 +0300 Subject: [PATCH 4/8] x86/mm/pat: don't collapse pages without PSE set Collapsing pages to a leaf PMD or PUD should be done only if X86_FEATURE_PSE is available, which is not the case when running e.g. as a Xen PV guest. Fixes: 41d88484c71c ("x86/mm/pat: restore large ROX pages after fragmentation") Signed-off-by: Juergen Gross Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250528123557.12847-3-jgross@suse.com --- arch/x86/mm/pat/set_memory.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c index 46edc11726b7..8834c76f91c9 100644 --- a/arch/x86/mm/pat/set_memory.c +++ b/arch/x86/mm/pat/set_memory.c @@ -1257,6 +1257,9 @@ static int collapse_pmd_page(pmd_t *pmd, unsigned long addr, pgprot_t pgprot; int i = 0; + if (!cpu_feature_enabled(X86_FEATURE_PSE)) + return 0; + addr &= PMD_MASK; pte = pte_offset_kernel(pmd, addr); first = *pte; From 47410d839fcda6890cb82828f874f97710982f24 Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Tue, 3 Jun 2025 14:14:42 +0300 Subject: [PATCH 5/8] x86/Kconfig: only enable ROX cache in execmem when STRICT_MODULE_RWX is set Currently ROX cache in execmem is enabled regardless of STRICT_MODULE_RWX setting. This breaks an assumption that module memory is writable when STRICT_MODULE_RWX is disabled, for instance for kernel debuggin. Only enable ROX cache in execmem when STRICT_MODULE_RWX is set to restore the original behaviour of module text permissions. Fixes: 64f6a4e10c05 ("x86: re-enable EXECMEM_ROX support") Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250603111446.2609381-3-rppt@kernel.org --- arch/x86/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 340e5468980e..71019b3b54ea 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -89,7 +89,7 @@ config X86 select ARCH_HAS_DMA_OPS if GART_IOMMU || XEN select ARCH_HAS_EARLY_DEBUG if KGDB select ARCH_HAS_ELF_RANDOMIZE - select ARCH_HAS_EXECMEM_ROX if X86_64 + select ARCH_HAS_EXECMEM_ROX if X86_64 && STRICT_MODULE_RWX select ARCH_HAS_FAST_MULTIPLIER select ARCH_HAS_FORTIFY_SOURCE select ARCH_HAS_GCOV_PROFILE_ALL From 0b0cae7119a0ec9449d7261b5e672a5fed765068 Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Tue, 3 Jun 2025 14:14:43 +0300 Subject: [PATCH 6/8] x86/its: move its_pages array to struct mod_arch_specific The of pages with ITS thunks allocated for modules are tracked by an array in 'struct module'. Since this is very architecture specific data structure, move it to 'struct mod_arch_specific'. No functional changes. Fixes: 872df34d7c51 ("x86/its: Use dynamic thunks for indirect branches") Suggested-by: Peter Zijlstra (Intel) Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250603111446.2609381-4-rppt@kernel.org --- arch/x86/include/asm/module.h | 8 ++++++++ arch/x86/kernel/alternative.c | 19 ++++++++++--------- include/linux/module.h | 5 ----- 3 files changed, 18 insertions(+), 14 deletions(-) diff --git a/arch/x86/include/asm/module.h b/arch/x86/include/asm/module.h index e988bac0a4a1..3c2de4ce3b10 100644 --- a/arch/x86/include/asm/module.h +++ b/arch/x86/include/asm/module.h @@ -5,12 +5,20 @@ #include #include +struct its_array { +#ifdef CONFIG_MITIGATION_ITS + void **pages; + int num; +#endif +}; + struct mod_arch_specific { #ifdef CONFIG_UNWINDER_ORC unsigned int num_orcs; int *orc_unwind_ip; struct orc_entry *orc_unwind; #endif + struct its_array its_pages; }; #endif /* _ASM_X86_MODULE_H */ diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index ecfe7b497cad..b50fe6ce4655 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -173,8 +173,8 @@ void its_fini_mod(struct module *mod) its_page = NULL; mutex_unlock(&text_mutex); - for (int i = 0; i < mod->its_num_pages; i++) { - void *page = mod->its_page_array[i]; + for (int i = 0; i < mod->arch.its_pages.num; i++) { + void *page = mod->arch.its_pages.pages[i]; execmem_restore_rox(page, PAGE_SIZE); } } @@ -184,11 +184,11 @@ void its_free_mod(struct module *mod) if (!cpu_feature_enabled(X86_FEATURE_INDIRECT_THUNK_ITS)) return; - for (int i = 0; i < mod->its_num_pages; i++) { - void *page = mod->its_page_array[i]; + for (int i = 0; i < mod->arch.its_pages.num; i++) { + void *page = mod->arch.its_pages.pages[i]; execmem_free(page); } - kfree(mod->its_page_array); + kfree(mod->arch.its_pages.pages); } #endif /* CONFIG_MODULES */ @@ -201,14 +201,15 @@ static void *its_alloc(void) #ifdef CONFIG_MODULES if (its_mod) { - void *tmp = krealloc(its_mod->its_page_array, - (its_mod->its_num_pages+1) * sizeof(void *), + struct its_array *pages = &its_mod->arch.its_pages; + void *tmp = krealloc(pages->pages, + (pages->num+1) * sizeof(void *), GFP_KERNEL); if (!tmp) return NULL; - its_mod->its_page_array = tmp; - its_mod->its_page_array[its_mod->its_num_pages++] = page; + pages->pages = tmp; + pages->pages[pages->num++] = page; execmem_make_temp_rw(page, PAGE_SIZE); } diff --git a/include/linux/module.h b/include/linux/module.h index 92e1420fccdf..5faa1fb1f4b4 100644 --- a/include/linux/module.h +++ b/include/linux/module.h @@ -586,11 +586,6 @@ struct module { atomic_t refcnt; #endif -#ifdef CONFIG_MITIGATION_ITS - int its_num_pages; - void **its_page_array; -#endif - #ifdef CONFIG_CONSTRUCTORS /* Constructor functions. */ ctor_fn_t *ctors; From a82b26451de126a5ae130361081986bc459afe9b Mon Sep 17 00:00:00 2001 From: "Peter Zijlstra (Intel)" Date: Tue, 3 Jun 2025 14:14:44 +0300 Subject: [PATCH 7/8] x86/its: explicitly manage permissions for ITS pages execmem_alloc() sets permissions differently depending on the kernel configuration, CPU support for PSE and whether a page is allocated before or after mark_rodata_ro(). Add tracking for pages allocated for ITS when patching the core kernel and make sure the permissions for ITS pages are explicitly managed for both kernel and module allocations. Fixes: 872df34d7c51 ("x86/its: Use dynamic thunks for indirect branches") Signed-off-by: Peter Zijlstra (Intel) Co-developed-by: Mike Rapoport (Microsoft) Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Nikolay Borisov Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250603111446.2609381-5-rppt@kernel.org --- arch/x86/kernel/alternative.c | 74 ++++++++++++++++++++++++----------- 1 file changed, 52 insertions(+), 22 deletions(-) diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index b50fe6ce4655..6455f7f751b3 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -116,6 +116,24 @@ static struct module *its_mod; #endif static void *its_page; static unsigned int its_offset; +struct its_array its_pages; + +static void *__its_alloc(struct its_array *pages) +{ + void *page __free(execmem) = execmem_alloc(EXECMEM_MODULE_TEXT, PAGE_SIZE); + if (!page) + return NULL; + + void *tmp = krealloc(pages->pages, (pages->num+1) * sizeof(void *), + GFP_KERNEL); + if (!tmp) + return NULL; + + pages->pages = tmp; + pages->pages[pages->num++] = page; + + return no_free_ptr(page); +} /* Initialize a thunk with the "jmp *reg; int3" instructions. */ static void *its_init_thunk(void *thunk, int reg) @@ -151,6 +169,21 @@ static void *its_init_thunk(void *thunk, int reg) return thunk + offset; } +static void its_pages_protect(struct its_array *pages) +{ + for (int i = 0; i < pages->num; i++) { + void *page = pages->pages[i]; + execmem_restore_rox(page, PAGE_SIZE); + } +} + +static void its_fini_core(void) +{ + if (IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) + its_pages_protect(&its_pages); + kfree(its_pages.pages); +} + #ifdef CONFIG_MODULES void its_init_mod(struct module *mod) { @@ -173,10 +206,8 @@ void its_fini_mod(struct module *mod) its_page = NULL; mutex_unlock(&text_mutex); - for (int i = 0; i < mod->arch.its_pages.num; i++) { - void *page = mod->arch.its_pages.pages[i]; - execmem_restore_rox(page, PAGE_SIZE); - } + if (IS_ENABLED(CONFIG_STRICT_MODULE_RWX)) + its_pages_protect(&mod->arch.its_pages); } void its_free_mod(struct module *mod) @@ -194,28 +225,23 @@ void its_free_mod(struct module *mod) static void *its_alloc(void) { - void *page __free(execmem) = execmem_alloc(EXECMEM_MODULE_TEXT, PAGE_SIZE); + struct its_array *pages = &its_pages; + void *page; +#ifdef CONFIG_MODULE + if (its_mod) + pages = &its_mod->arch.its_pages; +#endif + + page = __its_alloc(pages); if (!page) return NULL; -#ifdef CONFIG_MODULES - if (its_mod) { - struct its_array *pages = &its_mod->arch.its_pages; - void *tmp = krealloc(pages->pages, - (pages->num+1) * sizeof(void *), - GFP_KERNEL); - if (!tmp) - return NULL; + execmem_make_temp_rw(page, PAGE_SIZE); + if (pages == &its_pages) + set_memory_x((unsigned long)page, 1); - pages->pages = tmp; - pages->pages[pages->num++] = page; - - execmem_make_temp_rw(page, PAGE_SIZE); - } -#endif /* CONFIG_MODULES */ - - return no_free_ptr(page); + return page; } static void *its_allocate_thunk(int reg) @@ -269,7 +295,9 @@ u8 *its_static_thunk(int reg) return thunk; } -#endif +#else +static inline void its_fini_core(void) {} +#endif /* CONFIG_MITIGATION_ITS */ /* * Nomenclature for variable names to simplify and clarify this code and ease @@ -2339,6 +2367,8 @@ void __init alternative_instructions(void) apply_retpolines(__retpoline_sites, __retpoline_sites_end); apply_returns(__return_sites, __return_sites_end); + its_fini_core(); + /* * Adjust all CALL instructions to point to func()-10, including * those in .altinstr_replacement. From 7cd9a11dd0c3d1dd225795ed1b5b53132888e7b5 Mon Sep 17 00:00:00 2001 From: "Mike Rapoport (Microsoft)" Date: Tue, 3 Jun 2025 14:14:45 +0300 Subject: [PATCH 8/8] Revert "mm/execmem: Unify early execmem_cache behaviour" The commit d6d1e3e6580c ("mm/execmem: Unify early execmem_cache behaviour") changed early behaviour of execemem ROX cache to allow its usage in early x86 code that allocates text pages when CONFIG_MITGATION_ITS is enabled. The permission management of the pages allocated from execmem for ITS mitigation is now completely contained in arch/x86/kernel/alternatives.c and therefore there is no need to special case early allocations in execmem. This reverts commit d6d1e3e6580ca35071ad474381f053cbf1fb6414. Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Peter Zijlstra (Intel) Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20250603111446.2609381-6-rppt@kernel.org --- arch/x86/mm/init_32.c | 3 --- arch/x86/mm/init_64.c | 3 --- include/linux/execmem.h | 8 +------- mm/execmem.c | 40 +++------------------------------------- 4 files changed, 4 insertions(+), 50 deletions(-) diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 607d6a2e66e2..8a34fff6ab2b 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -30,7 +30,6 @@ #include #include #include -#include #include #include @@ -749,8 +748,6 @@ void mark_rodata_ro(void) pr_info("Write protecting kernel text and read-only data: %luk\n", size >> 10); - execmem_cache_make_ro(); - kernel_set_to_readonly = 1; #ifdef CONFIG_CPA_DEBUG diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index ee66fae9ebcc..fdb6cab524f0 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -34,7 +34,6 @@ #include #include #include -#include #include #include @@ -1392,8 +1391,6 @@ void mark_rodata_ro(void) (end - start) >> 10); set_memory_ro(start, (end - start) >> PAGE_SHIFT); - execmem_cache_make_ro(); - kernel_set_to_readonly = 1; /* diff --git a/include/linux/execmem.h b/include/linux/execmem.h index ca42d5e46ccc..3be35680a54f 100644 --- a/include/linux/execmem.h +++ b/include/linux/execmem.h @@ -54,7 +54,7 @@ enum execmem_range_flags { EXECMEM_ROX_CACHE = (1 << 1), }; -#if defined(CONFIG_ARCH_HAS_EXECMEM_ROX) && defined(CONFIG_EXECMEM) +#ifdef CONFIG_ARCH_HAS_EXECMEM_ROX /** * execmem_fill_trapping_insns - set memory to contain instructions that * will trap @@ -94,15 +94,9 @@ int execmem_make_temp_rw(void *ptr, size_t size); * Return: 0 on success or negative error code on failure. */ int execmem_restore_rox(void *ptr, size_t size); - -/* - * Called from mark_readonly(), where the system transitions to ROX. - */ -void execmem_cache_make_ro(void); #else static inline int execmem_make_temp_rw(void *ptr, size_t size) { return 0; } static inline int execmem_restore_rox(void *ptr, size_t size) { return 0; } -static inline void execmem_cache_make_ro(void) { } #endif /** diff --git a/mm/execmem.c b/mm/execmem.c index 9720ac2dfa41..2b683e7d864d 100644 --- a/mm/execmem.c +++ b/mm/execmem.c @@ -254,34 +254,6 @@ out_unlock: return ptr; } -static bool execmem_cache_rox = false; - -void execmem_cache_make_ro(void) -{ - struct maple_tree *free_areas = &execmem_cache.free_areas; - struct maple_tree *busy_areas = &execmem_cache.busy_areas; - MA_STATE(mas_free, free_areas, 0, ULONG_MAX); - MA_STATE(mas_busy, busy_areas, 0, ULONG_MAX); - struct mutex *mutex = &execmem_cache.mutex; - void *area; - - execmem_cache_rox = true; - - mutex_lock(mutex); - - mas_for_each(&mas_free, area, ULONG_MAX) { - unsigned long pages = mas_range_len(&mas_free) >> PAGE_SHIFT; - set_memory_ro(mas_free.index, pages); - } - - mas_for_each(&mas_busy, area, ULONG_MAX) { - unsigned long pages = mas_range_len(&mas_busy) >> PAGE_SHIFT; - set_memory_ro(mas_busy.index, pages); - } - - mutex_unlock(mutex); -} - static int execmem_cache_populate(struct execmem_range *range, size_t size) { unsigned long vm_flags = VM_ALLOW_HUGE_VMAP; @@ -302,15 +274,9 @@ static int execmem_cache_populate(struct execmem_range *range, size_t size) /* fill memory with instructions that will trap */ execmem_fill_trapping_insns(p, alloc_size, /* writable = */ true); - if (execmem_cache_rox) { - err = set_memory_rox((unsigned long)p, vm->nr_pages); - if (err) - goto err_free_mem; - } else { - err = set_memory_x((unsigned long)p, vm->nr_pages); - if (err) - goto err_free_mem; - } + err = set_memory_rox((unsigned long)p, vm->nr_pages); + if (err) + goto err_free_mem; err = execmem_cache_add(p, alloc_size); if (err)