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-rw-r--r--arch/riscv/kernel/traps.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 142f5f5168..05a16b1f0a 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -6,6 +6,7 @@
#include <linux/cpu.h>
#include <linux/kernel.h>
#include <linux/init.h>
+#include <linux/randomize_kstack.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/sched/signal.h>
@@ -310,7 +311,8 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
}
}
-asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs)
+asmlinkage __visible __trap_section __no_stack_protector
+void do_trap_ecall_u(struct pt_regs *regs)
{
if (user_mode(regs)) {
long syscall = regs->a7;
@@ -322,10 +324,23 @@ asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs)
syscall = syscall_enter_from_user_mode(regs, syscall);
+ add_random_kstack_offset();
+
if (syscall >= 0 && syscall < NR_syscalls)
syscall_handler(regs, syscall);
else if (syscall != -1)
regs->a0 = -ENOSYS;
+ /*
+ * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
+ * so the maximum stack offset is 1k bytes (10 bits).
+ *
+ * The actual entropy will be further reduced by the compiler when
+ * applying stack alignment constraints: 16-byte (i.e. 4-bit) aligned
+ * for RV32I or RV64I.
+ *
+ * The resulting 6 bits of entropy is seen in SP[9:4].
+ */
+ choose_random_kstack_offset(get_random_u16());
syscall_exit_to_user_mode(regs);
} else {