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authorRicardo Neri <ricardo.neri-calderon@linux.intel.com>2017-11-06 05:27:53 +0300
committerIngo Molnar <mingo@kernel.org>2017-11-08 13:16:22 +0300
commitc6a960bbf6a36572a06bde866d94a7338c7f256a (patch)
treee20d36753ac38b0fd48bb1cbce86271a229babb2 /arch/x86
parent1e5db223696afa55e6a038fac638f759e1fdcc01 (diff)
downloadlinux-c6a960bbf6a36572a06bde866d94a7338c7f256a.tar.xz
x86/umip: Force a page fault when unable to copy emulated result to user
fixup_umip_exception() will be called from do_general_protection(). If the former returns false, the latter will issue a SIGSEGV with SEND_SIG_PRIV. However, when emulation is successful but the emulated result cannot be copied to user space memory, it is more accurate to issue a SIGSEGV with SEGV_MAPERR with the offending address. A new function, inspired in force_sig_info_fault(), is introduced to model the page fault. Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Borislav Petkov <bp@suse.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Chen Yucong <slaoub@gmail.com> Cc: Chris Metcalf <cmetcalf@mellanox.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Huang Rui <ray.huang@amd.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Jonathan Corbet <corbet@lwn.net> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Michael S. Tsirkin <mst@redhat.com> Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi V. Shankar <ravi.v.shankar@intel.com> Cc: Shuah Khan <shuah@kernel.org> Cc: Tony Luck <tony.luck@intel.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: ricardo.neri@intel.com Link: http://lkml.kernel.org/r/1509935277-22138-9-git-send-email-ricardo.neri-calderon@linux.intel.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/umip.c49
1 files changed, 47 insertions, 2 deletions
diff --git a/arch/x86/kernel/umip.c b/arch/x86/kernel/umip.c
index d80b816228ea..6ba82be68cff 100644
--- a/arch/x86/kernel/umip.c
+++ b/arch/x86/kernel/umip.c
@@ -11,6 +11,10 @@
#include <asm/traps.h>
#include <asm/insn.h>
#include <asm/insn-eval.h>
+#include <linux/ratelimit.h>
+
+#undef pr_fmt
+#define pr_fmt(fmt) "umip: " fmt
/** DOC: Emulation for User-Mode Instruction Prevention (UMIP)
*
@@ -196,6 +200,41 @@ static int emulate_umip_insn(struct insn *insn, int umip_inst,
}
/**
+ * force_sig_info_umip_fault() - Force a SIGSEGV with SEGV_MAPERR
+ * @addr: Address that caused the signal
+ * @regs: Register set containing the instruction pointer
+ *
+ * Force a SIGSEGV signal with SEGV_MAPERR as the error code. This function is
+ * intended to be used to provide a segmentation fault when the result of the
+ * UMIP emulation could not be copied to the user space memory.
+ *
+ * Returns: none
+ */
+static void force_sig_info_umip_fault(void __user *addr, struct pt_regs *regs)
+{
+ siginfo_t info;
+ struct task_struct *tsk = current;
+
+ tsk->thread.cr2 = (unsigned long)addr;
+ tsk->thread.error_code = X86_PF_USER | X86_PF_WRITE;
+ tsk->thread.trap_nr = X86_TRAP_PF;
+
+ info.si_signo = SIGSEGV;
+ info.si_errno = 0;
+ info.si_code = SEGV_MAPERR;
+ info.si_addr = addr;
+ force_sig_info(SIGSEGV, &info, tsk);
+
+ 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);
+}
+
+/**
* fixup_umip_exception() - Fixup a general protection fault caused by UMIP
* @regs: Registers as saved when entering the #GP handler
*
@@ -311,8 +350,14 @@ bool fixup_umip_exception(struct pt_regs *regs)
return false;
nr_copied = copy_to_user(uaddr, dummy_data, dummy_data_size);
- if (nr_copied > 0)
- return false;
+ if (nr_copied > 0) {
+ /*
+ * If copy fails, send a signal and tell caller that
+ * fault was fixed up.
+ */
+ force_sig_info_umip_fault(uaddr, regs);
+ return true;
+ }
}
/* increase IP to let the program keep going */