]> git.proxmox.com Git - mirror_ubuntu-disco-kernel.git/commitdiff
ptrace: PTRACE_DETACH should do flush_ptrace_hw_breakpoint(child)
authorOleg Nesterov <oleg@redhat.com>
Mon, 8 Jul 2013 23:01:05 +0000 (16:01 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Tue, 9 Jul 2013 17:33:26 +0000 (10:33 -0700)
Change ptrace_detach() to call flush_ptrace_hw_breakpoint(child).  This
frees the slots for non-ptrace PERF_TYPE_BREAKPOINT users, and this
ensures that the tracee won't be killed by SIGTRAP triggered by the
active breakpoints.

Test-case:

unsigned long encode_dr7(int drnum, int enable, unsigned int type, unsigned int len)
{
unsigned long dr7;

dr7 = ((len | type) & 0xf)
<< (DR_CONTROL_SHIFT + drnum * DR_CONTROL_SIZE);
if (enable)
dr7 |= (DR_GLOBAL_ENABLE << (drnum * DR_ENABLE_SIZE));

return dr7;
}

int write_dr(int pid, int dr, unsigned long val)
{
return ptrace(PTRACE_POKEUSER, pid,
offsetof (struct user, u_debugreg[dr]),
val);
}

void func(void)
{
}

int main(void)
{
int pid, stat;
unsigned long dr7;

pid = fork();
if (!pid) {
assert(ptrace(PTRACE_TRACEME, 0,0,0) == 0);
kill(getpid(), SIGHUP);

func();
return 0x13;
}

assert(pid == waitpid(-1, &stat, 0));
assert(WSTOPSIG(stat) == SIGHUP);

assert(write_dr(pid, 0, (long)func) == 0);
dr7 = encode_dr7(0, 1, DR_RW_EXECUTE, DR_LEN_1);
assert(write_dr(pid, 7, dr7) == 0);

assert(ptrace(PTRACE_DETACH, pid, 0,0) == 0);
assert(pid == waitpid(-1, &stat, 0));
assert(stat == 0x1300);

return 0;
}

Before this patch the child is killed after PTRACE_DETACH.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jan Kratochvil <jan.kratochvil@redhat.com>
Cc: Michael Neuling <mikey@neuling.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
kernel/ptrace.c

index a146ee327f6ac15029b64424f0abd07e8d316f67..4041f5747e73bf70f8d8dbb412f8e7b7067a8017 100644 (file)
@@ -469,6 +469,7 @@ static int ptrace_detach(struct task_struct *child, unsigned int data)
        /* Architecture-specific hardware disable .. */
        ptrace_disable(child);
        clear_tsk_thread_flag(child, TIF_SYSCALL_TRACE);
+       flush_ptrace_hw_breakpoint(child);
 
        write_lock_irq(&tasklist_lock);
        /*