x86/ptrace: Remove set_segment_reg() implementations for current

seg_segment_reg() should be unreachable with task == current.
Rather than confusingly trying to make it work, just explicitly
disable this case.

(regset->get is used for current in the coredump code, but the ->set
 interface is only used for ptrace, and you can't ptrace yourself.)

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 066e5b0..3b3b169 100644 (file)
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -182,6 +182,9 @@ static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
 static int set_segment_reg(struct task_struct *task,
                           unsigned long offset, u16 value)
 {
+       if (WARN_ON_ONCE(task == current))
+               return -EIO;
+
        /*
         * The value argument was already truncated to 16 bits.
         */
@@ -209,10 +212,7 @@ static int set_segment_reg(struct task_struct *task,
                break;
 
        case offsetof(struct user_regs_struct, gs):
-               if (task == current)
-                       set_user_gs(task_pt_regs(task), value);
-               else
-                       task_user_gs(task) = value;
+               task_user_gs(task) = value;
        }
 
        return 0;
@@ -272,6 +272,9 @@ static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
 static int set_segment_reg(struct task_struct *task,
                           unsigned long offset, u16 value)
 {
+       if (WARN_ON_ONCE(task == current))
+               return -EIO;
+
        /*
         * The value argument was already truncated to 16 bits.
         */
@@ -281,23 +284,15 @@ static int set_segment_reg(struct task_struct *task,
        switch (offset) {
        case offsetof(struct user_regs_struct,fs):
                task->thread.fsindex = value;
-               if (task == current)
-                       loadsegment(fs, task->thread.fsindex);
                break;
        case offsetof(struct user_regs_struct,gs):
                task->thread.gsindex = value;
-               if (task == current)
-                       load_gs_index(task->thread.gsindex);
                break;
        case offsetof(struct user_regs_struct,ds):
                task->thread.ds = value;
-               if (task == current)
-                       loadsegment(ds, task->thread.ds);
                break;
        case offsetof(struct user_regs_struct,es):
                task->thread.es = value;
-               if (task == current)
-                       loadsegment(es, task->thread.es);
                break;
 
                /*