From 8e05f1b4f27d07a0f93e7c6fd28525a5d082b85c Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Mon, 15 Jul 2019 10:08:48 -0700 Subject: [PATCH] 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 Cc: Borislav Petkov Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Linus Torvalds Signed-off-by: Ingo Molnar --- arch/x86/kernel/ptrace.c | 19 +++++++------------ 1 file changed, 7 insertions(+), 12 deletions(-) diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 066e5b01a7e0..3b3b16932589 100644 --- 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; /* -- 2.45.2