arm64: ptrace: fix compat reg getter/setter return values

copy_{to,from}_user return the number of bytes remaining on failure, not
an error code.

This patch returns -EFAULT when the copy operation didn't complete,
rather than expose the number of bytes not copied directly to userspace.

Signed-off-by: Will Deacon <will.deacon@arm.com>

1 files changed, 7 insertions, 3 deletions

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 2ac998878001..fe63ac5e9bf5 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -663,8 +663,10 @@ static int compat_gpr_get(struct task_struct *target,
                         kbuf += sizeof(reg);
                 } else {
                         ret = copy_to_user(ubuf, &reg, sizeof(reg));
-                        if (ret)
+                        if (ret) {
+                                ret = -EFAULT;
                                 break;
+                        }
 
                         ubuf += sizeof(reg);
                 }
@@ -702,8 +704,10 @@ static int compat_gpr_set(struct task_struct *target,
                         kbuf += sizeof(reg);
                 } else {
                         ret = copy_from_user(&reg, ubuf, sizeof(reg));
-                        if (ret)
-                                return ret;
+                        if (ret) {
+                                ret = -EFAULT;
+                                break;
+                        }
 
                         ubuf += sizeof(reg);
                 }