From: Peter Zijlstra peterz@infradead.org
stable inclusion from stable-5.10.81 commit b31bac061918936d6f6d647878bd45a2c81b446b bugzilla: 185832 https://gitee.com/openeuler/kernel/issues/I4L9CF
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...
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commit b968e84b509da593c50dc3db679e1d33de701f78 upstream.
Since commit c8137ace5638 ("x86/iopl: Restrict iopl() permission scope") it's possible to emulate iopl(3) using ioperm(), except for the CLI/STI usage.
Userspace CLI/STI usage is very dubious (read broken), since any exception taken during that window can lead to rescheduling anyway (or worse). The IOPL(2) manpage even states that usage of CLI/STI is highly discouraged and might even crash the system.
Of course, that won't stop people and HP has the dubious honour of being the first vendor to be found using this in their hp-health package.
In order to enable this 'software' to still 'work', have the #GP treat the CLI/STI instructions as NOPs when iopl(3). Warn the user that their program is doing dubious things.
Fixes: a24ca9976843 ("x86/iopl: Remove legacy IOPL option") Reported-by: Ondrej Zary linux@zary.sk Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reviewed-by: Thomas Gleixner tglx@linutronix.de Cc: stable@kernel.org # v5.5+ Link: https://lkml.kernel.org/r/20210918090641.GD5106@worktop.programming.kicks-as... Signed-off-by: Ondrej Zary linux@zary.sk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Chen Jun chenjun102@huawei.com Acked-by: Weilong Chen chenweilong@huawei.com
Signed-off-by: Chen Jun chenjun102@huawei.com --- arch/x86/include/asm/insn-eval.h | 1 + arch/x86/include/asm/processor.h | 1 + arch/x86/kernel/process.c | 1 + arch/x86/kernel/traps.c | 34 ++++++++++++++++++++++++++++++++ arch/x86/lib/insn-eval.c | 2 +- 5 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/arch/x86/include/asm/insn-eval.h b/arch/x86/include/asm/insn-eval.h index 98b4dae5e8bc..c1438f9239e4 100644 --- a/arch/x86/include/asm/insn-eval.h +++ b/arch/x86/include/asm/insn-eval.h @@ -21,6 +21,7 @@ int insn_get_modrm_rm_off(struct insn *insn, struct pt_regs *regs); int insn_get_modrm_reg_off(struct insn *insn, struct pt_regs *regs); unsigned long insn_get_seg_base(struct pt_regs *regs, int seg_reg_idx); int insn_get_code_seg_params(struct pt_regs *regs); +unsigned long insn_get_effective_ip(struct pt_regs *regs); int insn_fetch_from_user(struct pt_regs *regs, unsigned char buf[MAX_INSN_SIZE]); int insn_fetch_from_user_inatomic(struct pt_regs *regs, diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 50d02db72317..d428d611a43a 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -534,6 +534,7 @@ struct thread_struct { */ unsigned long iopl_emul;
+ unsigned int iopl_warn:1; unsigned int sig_on_uaccess_err:1;
/* Floating point and extended processor state */ diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index d7f23d1c7391..035cd1e1ede5 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -138,6 +138,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg, frame->ret_addr = (unsigned long) ret_from_fork; p->thread.sp = (unsigned long) fork_frame; p->thread.io_bitmap = NULL; + p->thread.iopl_warn = 0; memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
#ifdef CONFIG_X86_64 diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 143fcb8af38f..2d4ecd50e69b 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -523,6 +523,37 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs,
#define GPFSTR "general protection fault"
+static bool fixup_iopl_exception(struct pt_regs *regs) +{ + struct thread_struct *t = ¤t->thread; + unsigned char byte; + unsigned long ip; + + if (!IS_ENABLED(CONFIG_X86_IOPL_IOPERM) || t->iopl_emul != 3) + return false; + + ip = insn_get_effective_ip(regs); + if (!ip) + return false; + + if (get_user(byte, (const char __user *)ip)) + return false; + + if (byte != 0xfa && byte != 0xfb) + return false; + + if (!t->iopl_warn && printk_ratelimit()) { + pr_err("%s[%d] attempts to use CLI/STI, pretending it's a NOP, ip:%lx", + current->comm, task_pid_nr(current), ip); + print_vma_addr(KERN_CONT " in ", ip); + pr_cont("\n"); + t->iopl_warn = 1; + } + + regs->ip += 1; + return true; +} + DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) { char desc[sizeof(GPFSTR) + 50 + 2*sizeof(unsigned long) + 1] = GPFSTR; @@ -548,6 +579,9 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection) tsk = current;
if (user_mode(regs)) { + if (fixup_iopl_exception(regs)) + goto exit; + tsk->thread.error_code = error_code; tsk->thread.trap_nr = X86_TRAP_GP;
diff --git a/arch/x86/lib/insn-eval.c b/arch/x86/lib/insn-eval.c index bb0b3fe1e0a0..c6a19c88af54 100644 --- a/arch/x86/lib/insn-eval.c +++ b/arch/x86/lib/insn-eval.c @@ -1415,7 +1415,7 @@ void __user *insn_get_addr_ref(struct insn *insn, struct pt_regs *regs) } }
-static unsigned long insn_get_effective_ip(struct pt_regs *regs) +unsigned long insn_get_effective_ip(struct pt_regs *regs) { unsigned long seg_base = 0;