metag/ptrace: Provide default TXSTATUS for short NT_PRSTATUS

Ensure that if userspace supplies insufficient data to PTRACE_SETREGSET
to fill TXSTATUS, a well-defined default value is used, based on the
task's current value.

Suggested-by: James Hogan <james.hogan@imgtec.com>
Signed-off-by: Dave Martin <Dave.Martin@arm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 12 insertions, 3 deletions

diff --git a/arch/metag/kernel/ptrace.c b/arch/metag/kernel/ptrace.c
index ae659ba61948..2e4dfc15abd3 100644
--- a/arch/metag/kernel/ptrace.c
+++ b/arch/metag/kernel/ptrace.c
@@ -24,6 +24,16 @@
  * user_regset definitions.
  */
 
+static unsigned long user_txstatus(const struct pt_regs *regs)
+{
+        unsigned long data = (unsigned long)regs->ctx.Flags;
+
+        if (regs->ctx.SaveMask & TBICTX_CBUF_BIT)
+                data |= USER_GP_REGS_STATUS_CATCH_BIT;
+
+        return data;
+}
+
 int metag_gp_regs_copyout(const struct pt_regs *regs,
                           unsigned int pos, unsigned int count,
                           void *kbuf, void __user *ubuf)
@@ -62,9 +72,7 @@ int metag_gp_regs_copyout(const struct pt_regs *regs,
         if (ret)
                 goto out;
         /* TXSTATUS */
-        data = (unsigned long)regs->ctx.Flags;
-        if (regs->ctx.SaveMask & TBICTX_CBUF_BIT)
-                data |= USER_GP_REGS_STATUS_CATCH_BIT;
+        data = user_txstatus(regs);
         ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                   &data, 4*25, 4*26);
         if (ret)
@@ -119,6 +127,7 @@ int metag_gp_regs_copyin(struct pt_regs *regs,
         if (ret)
                 goto out;
         /* TXSTATUS */
+        data = user_txstatus(regs);
         ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                  &data, 4*25, 4*26);
         if (ret)