openrisc: traps: Don't send signals to kernel mode threads

[ Upstream commit c88cfb5cea5f8f9868ef02cc9ce9183a26dcf20f ]

OpenRISC exception handling sends signals to user processes on floating
point exceptions and trap instructions (for debugging) among others.
There is a bug where the trap handling logic may send signals to kernel
threads, we should not send these signals to kernel threads, if that
happens we treat it as an error.

This patch adds conditions to die if the kernel receives these
exceptions in kernel mode code.

Fixes: 27267655c531 ("openrisc: Support floating point user api")
Signed-off-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index 9370888c9a7e310c07fe829769dd41d3c0cdeafb..90554a5558fbcae01ef086991a40b60798c2c283 100644 (file)
--- a/arch/openrisc/kernel/traps.c
+++ b/arch/openrisc/kernel/traps.c
@@ -180,29 +180,39 @@ asmlinkage void unhandled_exception(struct pt_regs *regs, int ea, int vector)
 
 asmlinkage void do_fpe_trap(struct pt_regs *regs, unsigned long address)
 {
-       int code = FPE_FLTUNK;
-       unsigned long fpcsr = regs->fpcsr;
-
-       if (fpcsr & SPR_FPCSR_IVF)
-               code = FPE_FLTINV;
-       else if (fpcsr & SPR_FPCSR_OVF)
-               code = FPE_FLTOVF;
-       else if (fpcsr & SPR_FPCSR_UNF)
-               code = FPE_FLTUND;
-       else if (fpcsr & SPR_FPCSR_DZF)
-               code = FPE_FLTDIV;
-       else if (fpcsr & SPR_FPCSR_IXF)
-               code = FPE_FLTRES;
-
-       /* Clear all flags */
-       regs->fpcsr &= ~SPR_FPCSR_ALLF;
-
-       force_sig_fault(SIGFPE, code, (void __user *)regs->pc);
+       if (user_mode(regs)) {
+               int code = FPE_FLTUNK;
+               unsigned long fpcsr = regs->fpcsr;
+
+               if (fpcsr & SPR_FPCSR_IVF)
+                       code = FPE_FLTINV;
+               else if (fpcsr & SPR_FPCSR_OVF)
+                       code = FPE_FLTOVF;
+               else if (fpcsr & SPR_FPCSR_UNF)
+                       code = FPE_FLTUND;
+               else if (fpcsr & SPR_FPCSR_DZF)
+                       code = FPE_FLTDIV;
+               else if (fpcsr & SPR_FPCSR_IXF)
+                       code = FPE_FLTRES;
+
+               /* Clear all flags */
+               regs->fpcsr &= ~SPR_FPCSR_ALLF;
+
+               force_sig_fault(SIGFPE, code, (void __user *)regs->pc);
+       } else {
+               pr_emerg("KERNEL: Illegal fpe exception 0x%.8lx\n", regs->pc);
+               die("Die:", regs, SIGFPE);
+       }
 }
 
 asmlinkage void do_trap(struct pt_regs *regs, unsigned long address)
 {
-       force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
+       if (user_mode(regs)) {
+               force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->pc);
+       } else {
+               pr_emerg("KERNEL: Illegal trap exception 0x%.8lx\n", regs->pc);
+               die("Die:", regs, SIGILL);
+       }
 }
 
 asmlinkage void do_unaligned_access(struct pt_regs *regs, unsigned long address)