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Diffstat (limited to 'arch/x86/kernel/umip.c')
-rw-r--r--arch/x86/kernel/umip.c88
1 files changed, 75 insertions, 13 deletions
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index 6ba82be68cff..f44ce0fb3583 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -78,7 +78,60 @@
#define UMIP_INST_SGDT 0 /* 0F 01 /0 */
#define UMIP_INST_SIDT 1 /* 0F 01 /1 */
-#define UMIP_INST_SMSW 3 /* 0F 01 /4 */
+#define UMIP_INST_SMSW 2 /* 0F 01 /4 */
+#define UMIP_INST_SLDT 3 /* 0F 00 /0 */
+#define UMIP_INST_STR 4 /* 0F 00 /1 */
+
+const char * const umip_insns[5] = {
+ [UMIP_INST_SGDT] = "SGDT",
+ [UMIP_INST_SIDT] = "SIDT",
+ [UMIP_INST_SMSW] = "SMSW",
+ [UMIP_INST_SLDT] = "SLDT",
+ [UMIP_INST_STR] = "STR",
+};
+
+#define umip_pr_err(regs, fmt, ...) \
+ umip_printk(regs, KERN_ERR, fmt, ##__VA_ARGS__)
+#define umip_pr_warning(regs, fmt, ...) \
+ umip_printk(regs, KERN_WARNING, fmt, ##__VA_ARGS__)
+
+/**
+ * umip_printk() - Print a rate-limited message
+ * @regs: Register set with the context in which the warning is printed
+ * @log_level: Kernel log level to print the message
+ * @fmt: The text string to print
+ *
+ * Print the text contained in @fmt. The print rate is limited to bursts of 5
+ * messages every two minutes. The purpose of this customized version of
+ * printk() is to print messages when user space processes use any of the
+ * UMIP-protected instructions. Thus, the printed text is prepended with the
+ * task name and process ID number of the current task as well as the
+ * instruction and stack pointers in @regs as seen when entering kernel mode.
+ *
+ * Returns:
+ *
+ * None.
+ */
+static __printf(3, 4)
+void umip_printk(const struct pt_regs *regs, const char *log_level,
+ const char *fmt, ...)
+{
+ /* Bursts of 5 messages every two minutes */
+ static DEFINE_RATELIMIT_STATE(ratelimit, 2 * 60 * HZ, 5);
+ struct task_struct *tsk = current;
+ struct va_format vaf;
+ va_list args;
+
+ if (!__ratelimit(&ratelimit))
+ return;
+
+ va_start(args, fmt);
+ vaf.fmt = fmt;
+ vaf.va = &args;
+ printk("%s" pr_fmt("%s[%d] ip:%lx sp:%lx: %pV"), log_level, tsk->comm,
+ task_pid_nr(tsk), regs->ip, regs->sp, &vaf);
+ va_end(args);
+}
/**
* identify_insn() - Identify a UMIP-protected instruction
@@ -118,10 +171,16 @@ static int identify_insn(struct insn *insn)
default:
return -EINVAL;
}
+ } else if (insn->opcode.bytes[1] == 0x0) {
+ if (X86_MODRM_REG(insn->modrm.value) == 0)
+ return UMIP_INST_SLDT;
+ else if (X86_MODRM_REG(insn->modrm.value) == 1)
+ return UMIP_INST_STR;
+ else
+ return -EINVAL;
+ } else {
+ return -EINVAL;
}
-
- /* SLDT AND STR are not emulated */
- return -EINVAL;
}
/**
@@ -228,10 +287,8 @@ static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs)
if (!(show_unhandled_signals && unhandled_signal(tsk, SIGSEGV)))
return;
- pr_err_ratelimited("%s[%d] umip emulation segfault ip:%lx sp:%lx error:%x in %lx\n",
- tsk->comm, task_pid_nr(tsk), regs->ip,
- regs->sp, X86_PF_USER | X86_PF_WRITE,
- regs->ip);
+ umip_pr_err(regs, "segfault in emulation. error%x\n",
+ X86_PF_USER | X86_PF_WRITE);
}
/**
@@ -262,15 +319,11 @@ bool fixup_umip_exception(struct pt_regs *regs)
unsigned char buf[MAX_INSN_SIZE];
void __user *uaddr;
struct insn insn;
- char seg_defs;
+ int seg_defs;
if (!regs)
return false;
- /* Do not emulate 64-bit processes. */
- if (user_64bit_mode(regs))
- return false;
-
/*
* If not in user-space long mode, a custom code segment could be in
* use. This is true in protected mode (if the process defined a local
@@ -322,6 +375,15 @@ bool fixup_umip_exception(struct pt_regs *regs)
if (umip_inst < 0)
return false;
+ umip_pr_warning(regs, "%s instruction cannot be used by applications.\n",
+ umip_insns[umip_inst]);
+
+ /* Do not emulate SLDT, STR or user long mode processes. */
+ if (umip_inst == UMIP_INST_STR || umip_inst == UMIP_INST_SLDT || user_64bit_mode(regs))
+ return false;
+
+ umip_pr_warning(regs, "For now, expensive software emulation returns the result.\n");
+
if (emulate_umip_insn(&insn, umip_inst, dummy_data, &dummy_data_size))
return false;