This is broken since ever but sadly nobody noticed. Recent versions of GDB set DR_CONTROL unconditionally and UML dies due to a heap corruption. It turns out that the PTRACE_POKEUSER was copy&pasted from i386 and assumes that addresses are 4 bytes long. Fix that by using 8 as address size in the calculation. Cc: <stable@xxxxxxxxxxxxxxx> Reported-by: jie cao <cj3054@xxxxxxxxx> Signed-off-by: Richard Weinberger <richard@xxxxxx> --- arch/x86/um/ptrace_64.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/um/ptrace_64.c b/arch/x86/um/ptrace_64.c index a5c9910d234f..09a085bde0d4 100644 --- a/arch/x86/um/ptrace_64.c +++ b/arch/x86/um/ptrace_64.c @@ -125,7 +125,7 @@ int poke_user(struct task_struct *child, long addr, long data) else if ((addr >= offsetof(struct user, u_debugreg[0])) && (addr <= offsetof(struct user, u_debugreg[7]))) { addr -= offsetof(struct user, u_debugreg[0]); - addr = addr >> 2; + addr = addr >> 3; if ((addr == 4) || (addr == 5)) return -EIO; child->thread.arch.debugregs[addr] = data; -- 2.10.2