From a3f547addcaa10df5a226526bc9e2d9a94542344 Mon Sep 17 00:00:00 2001 From: Michal Koutný Date: Mon, 6 Mar 2023 20:31:44 +0100 Subject: x86/mm: Do not shuffle CPU entry areas without KASLR MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The commit 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") fixed an omission of KASLR on CPU entry areas. It doesn't take into account KASLR switches though, which may result in unintended non-determinism when a user wants to avoid it (e.g. debugging, benchmarking). Generate only a single combination of CPU entry areas offsets -- the linear array that existed prior randomization when KASLR is turned off. Since we have 3f148f331814 ("x86/kasan: Map shadow for percpu pages on demand") and followups, we can use the more relaxed guard kasrl_enabled() (in contrast to kaslr_memory_enabled()). Fixes: 97e3d26b5e5f ("x86/mm: Randomize per-cpu entry area") Signed-off-by: Michal Koutný Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230306193144.24605-1-mkoutny%40suse.com --- arch/x86/mm/cpu_entry_area.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/mm/cpu_entry_area.c b/arch/x86/mm/cpu_entry_area.c index 7316a8224259..e91500a80963 100644 --- a/arch/x86/mm/cpu_entry_area.c +++ b/arch/x86/mm/cpu_entry_area.c @@ -10,6 +10,7 @@ #include #include #include +#include static DEFINE_PER_CPU_PAGE_ALIGNED(struct entry_stack_page, entry_stack_storage); @@ -29,6 +30,12 @@ static __init void init_cea_offsets(void) unsigned int max_cea; unsigned int i, j; + if (!kaslr_enabled()) { + for_each_possible_cpu(i) + per_cpu(_cea_offset, i) = i; + return; + } + max_cea = (CPU_ENTRY_AREA_MAP_SIZE - PAGE_SIZE) / CPU_ENTRY_AREA_SIZE; /* O(sodding terrible) */ -- cgit v1.2.3-58-ga151 From b15888840207c2bfe678dd1f68a32db54315e71f Mon Sep 17 00:00:00 2001 From: "Chang S. Bae" Date: Mon, 27 Feb 2023 13:05:03 -0800 Subject: x86/fpu/xstate: Prevent false-positive warning in __copy_xstate_uabi_buf() __copy_xstate_to_uabi_buf() copies either from the tasks XSAVE buffer or from init_fpstate into the ptrace buffer. Dynamic features, like XTILEDATA, have an all zeroes init state and are not saved in init_fpstate, which means the corresponding bit is not set in the xfeatures bitmap of the init_fpstate header. But __copy_xstate_to_uabi_buf() retrieves addresses for both the tasks xstate and init_fpstate unconditionally via __raw_xsave_addr(). So if the tasks XSAVE buffer has a dynamic feature set, then the address retrieval for init_fpstate triggers the warning in __raw_xsave_addr() which checks the feature bit in the init_fpstate header. Remove the address retrieval from init_fpstate for extended features. They have an all zeroes init state so init_fpstate has zeros for them. Then zeroing the user buffer for the init state is the same as copying them from init_fpstate. Fixes: 2308ee57d93d ("x86/fpu/amx: Enable the AMX feature in 64-bit mode") Reported-by: Mingwei Zhang Link: https://lore.kernel.org/kvm/20230221163655.920289-2-mizhang@google.com/ Signed-off-by: Chang S. Bae Signed-off-by: Dave Hansen Tested-by: Mingwei Zhang Link: https://lore.kernel.org/all/20230227210504.18520-2-chang.seok.bae%40intel.com Cc: stable@vger.kernel.org --- arch/x86/kernel/fpu/xstate.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 714166cc25f2..0bab497c9436 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1118,21 +1118,20 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate, zerofrom = offsetof(struct xregs_state, extended_state_area); /* - * The ptrace buffer is in non-compacted XSAVE format. In - * non-compacted format disabled features still occupy state space, - * but there is no state to copy from in the compacted - * init_fpstate. The gap tracking will zero these states. - */ - mask = fpstate->user_xfeatures; - - /* - * Dynamic features are not present in init_fpstate. When they are - * in an all zeros init state, remove those from 'mask' to zero - * those features in the user buffer instead of retrieving them - * from init_fpstate. + * This 'mask' indicates which states to copy from fpstate. + * Those extended states that are not present in fpstate are + * either disabled or initialized: + * + * In non-compacted format, disabled features still occupy + * state space but there is no state to copy from in the + * compacted init_fpstate. The gap tracking will zero these + * states. + * + * The extended features have an all zeroes init state. Thus, + * remove them from 'mask' to zero those features in the user + * buffer instead of retrieving them from init_fpstate. */ - if (fpu_state_size_dynamic()) - mask &= (header.xfeatures | xinit->header.xcomp_bv); + mask = header.xfeatures; for_each_extended_xfeature(i, mask) { /* @@ -1151,9 +1150,8 @@ void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate, pkru.pkru = pkru_val; membuf_write(&to, &pkru, sizeof(pkru)); } else { - copy_feature(header.xfeatures & BIT_ULL(i), &to, + membuf_write(&to, __raw_xsave_addr(xsave, i), - __raw_xsave_addr(xinit, i), xstate_sizes[i]); } /* -- cgit v1.2.3-58-ga151 From 62faca1ca10cc84e99ae7f38aa28df2bc945369b Mon Sep 17 00:00:00 2001 From: "Chang S. Bae" Date: Mon, 27 Feb 2023 13:05:04 -0800 Subject: selftests/x86/amx: Add a ptrace test Include a test case to validate the XTILEDATA injection to the target. Also, it ensures the kernel's ability to copy states between different XSAVE formats. Refactor the memcmp() code to be usable for the state validation. Signed-off-by: Chang S. Bae Signed-off-by: Dave Hansen Cc: stable@vger.kernel.org Link: https://lore.kernel.org/all/20230227210504.18520-3-chang.seok.bae%40intel.com --- tools/testing/selftests/x86/amx.c | 108 ++++++++++++++++++++++++++++++++++++-- 1 file changed, 105 insertions(+), 3 deletions(-) diff --git a/tools/testing/selftests/x86/amx.c b/tools/testing/selftests/x86/amx.c index 625e42901237..d884fd69dd51 100644 --- a/tools/testing/selftests/x86/amx.c +++ b/tools/testing/selftests/x86/amx.c @@ -14,8 +14,10 @@ #include #include #include +#include #include #include +#include #include "../kselftest.h" /* For __cpuid_count() */ @@ -583,6 +585,13 @@ static void test_dynamic_state(void) _exit(0); } +static inline int __compare_tiledata_state(struct xsave_buffer *xbuf1, struct xsave_buffer *xbuf2) +{ + return memcmp(&xbuf1->bytes[xtiledata.xbuf_offset], + &xbuf2->bytes[xtiledata.xbuf_offset], + xtiledata.size); +} + /* * Save current register state and compare it to @xbuf1.' * @@ -599,9 +608,7 @@ static inline bool __validate_tiledata_regs(struct xsave_buffer *xbuf1) fatal_error("failed to allocate XSAVE buffer\n"); xsave(xbuf2, XFEATURE_MASK_XTILEDATA); - ret = memcmp(&xbuf1->bytes[xtiledata.xbuf_offset], - &xbuf2->bytes[xtiledata.xbuf_offset], - xtiledata.size); + ret = __compare_tiledata_state(xbuf1, xbuf2); free(xbuf2); @@ -826,6 +833,99 @@ static void test_context_switch(void) free(finfo); } +/* Ptrace test */ + +/* + * Make sure the ptracee has the expanded kernel buffer on the first + * use. Then, initialize the state before performing the state + * injection from the ptracer. + */ +static inline void ptracee_firstuse_tiledata(void) +{ + load_rand_tiledata(stashed_xsave); + init_xtiledata(); +} + +/* + * Ptracer injects the randomized tile data state. It also reads + * before and after that, which will execute the kernel's state copy + * functions. So, the tester is advised to double-check any emitted + * kernel messages. + */ +static void ptracer_inject_tiledata(pid_t target) +{ + struct xsave_buffer *xbuf; + struct iovec iov; + + xbuf = alloc_xbuf(); + if (!xbuf) + fatal_error("unable to allocate XSAVE buffer"); + + printf("\tRead the init'ed tiledata via ptrace().\n"); + + iov.iov_base = xbuf; + iov.iov_len = xbuf_size; + + memset(stashed_xsave, 0, xbuf_size); + + if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov)) + fatal_error("PTRACE_GETREGSET"); + + if (!__compare_tiledata_state(stashed_xsave, xbuf)) + printf("[OK]\tThe init'ed tiledata was read from ptracee.\n"); + else + printf("[FAIL]\tThe init'ed tiledata was not read from ptracee.\n"); + + printf("\tInject tiledata via ptrace().\n"); + + load_rand_tiledata(xbuf); + + memcpy(&stashed_xsave->bytes[xtiledata.xbuf_offset], + &xbuf->bytes[xtiledata.xbuf_offset], + xtiledata.size); + + if (ptrace(PTRACE_SETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov)) + fatal_error("PTRACE_SETREGSET"); + + if (ptrace(PTRACE_GETREGSET, target, (uint32_t)NT_X86_XSTATE, &iov)) + fatal_error("PTRACE_GETREGSET"); + + if (!__compare_tiledata_state(stashed_xsave, xbuf)) + printf("[OK]\tTiledata was correctly written to ptracee.\n"); + else + printf("[FAIL]\tTiledata was not correctly written to ptracee.\n"); +} + +static void test_ptrace(void) +{ + pid_t child; + int status; + + child = fork(); + if (child < 0) { + err(1, "fork"); + } else if (!child) { + if (ptrace(PTRACE_TRACEME, 0, NULL, NULL)) + err(1, "PTRACE_TRACEME"); + + ptracee_firstuse_tiledata(); + + raise(SIGTRAP); + _exit(0); + } + + do { + wait(&status); + } while (WSTOPSIG(status) != SIGTRAP); + + ptracer_inject_tiledata(child); + + ptrace(PTRACE_DETACH, child, NULL, NULL); + wait(&status); + if (!WIFEXITED(status) || WEXITSTATUS(status)) + err(1, "ptrace test"); +} + int main(void) { /* Check hardware availability at first */ @@ -846,6 +946,8 @@ int main(void) ctxtswtest_config.num_threads = 5; test_context_switch(); + test_ptrace(); + clearhandler(SIGILL); free_stashed_xsave(); -- cgit v1.2.3-58-ga151