Patch "openrisc: traps: Don't send signals to kernel mode threads" has been added to the 6.8-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

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

to the 6.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     openrisc-traps-don-t-send-signals-to-kernel-mode-thr.patch
and it can be found in the queue-6.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit fc658e186d3a2b4a4efc2c6dad3d026df55af964
Author: Stafford Horne <shorne@xxxxxxxxx>
Date:   Sat Mar 30 14:42:49 2024 +0000

    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@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/openrisc/kernel/traps.c b/arch/openrisc/kernel/traps.c
index 9370888c9a7e3..90554a5558fbc 100644
--- 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)