From a6d9692cadb936e44c525e1335ff23daaf8a2cec Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 14 Feb 2022 13:05:49 +0100 Subject: [PATCH] x86/ptrace: Fix xfpregs_set()'s incorrect xmm clearing MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit 44cad52cc14ae10062f142ec16ede489bccf4469 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- 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 66ed317ebc0d3..125cbbe10fefa 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -87,11 +87,9 @@ 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; @@ -112,9 +110,10 @@ int xfpregs_set(struct task_struct *target, const struct user_regset *regset, /* Copy the state */ memcpy(&fpu->state.fxsave, &newstate, sizeof(newstate)); - /* Clear xmm8..15 */ + /* Clear xmm8..15 for 32-bit callers */ BUILD_BUG_ON(sizeof(fpu->state.fxsave.xmm_space) != 16 * 16); - memset(&fpu->state.fxsave.xmm_space[8], 0, 8 * 16); + if (in_ia32_syscall()) + memset(&fpu->state.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 4c208ea3bd9f3..033d9c6a94689 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 },