diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2022-04-29 09:23:55 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-06-09 10:22:29 +0200 |
| commit | 83d0ed00cca80d29750572d5e6125f74911ba42c (patch) | |
| tree | c092ecad8947327968a17fa005a8dacfee5f05b3 /arch | |
| parent | 7400a7e0a7ae1f1cd22250f0bfa1453f59a1d117 (diff) | |
ptrace: Reimplement PTRACE_KILL by always sending SIGKILL
commit 6a2d90ba027adba528509ffa27097cffd3879257 upstream.
The current implementation of PTRACE_KILL is buggy and has been for
many years as it assumes it's target has stopped in ptrace_stop. At a
quick skim it looks like this assumption has existed since ptrace
support was added in linux v1.0.
While PTRACE_KILL has been deprecated we can not remove it as
a quick search with google code search reveals many existing
programs calling it.
When the ptracee is not stopped at ptrace_stop some fields would be
set that are ignored except in ptrace_stop. Making the userspace
visible behavior of PTRACE_KILL a noop in those case.
As the usual rules are not obeyed it is not clear what the
consequences are of calling PTRACE_KILL on a running process.
Presumably userspace does not do this as it achieves nothing.
Replace the implementation of PTRACE_KILL with a simple
send_sig_info(SIGKILL) followed by a return 0. This changes the
observable user space behavior only in that PTRACE_KILL on a process
not stopped in ptrace_stop will also kill it. As that has always
been the intent of the code this seems like a reasonable change.
Cc: stable@vger.kernel.org
Reported-by: Al Viro <viro@zeniv.linux.org.uk>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Tested-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Oleg Nesterov <oleg@redhat.com>
Link: https://lkml.kernel.org/r/20220505182645.497868-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/step.c | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/arch/x86/kernel/step.c b/arch/x86/kernel/step.c index 0f3c307b37b3..8e2b2552b5ee 100644 --- a/arch/x86/kernel/step.c +++ b/arch/x86/kernel/step.c @@ -180,8 +180,7 @@ void set_task_blockstep(struct task_struct *task, bool on) * * NOTE: this means that set/clear TIF_BLOCKSTEP is only safe if * task is current or it can't be running, otherwise we can race - * with __switch_to_xtra(). We rely on ptrace_freeze_traced() but - * PTRACE_KILL is not safe. + * with __switch_to_xtra(). We rely on ptrace_freeze_traced(). */ local_irq_disable(); debugctl = get_debugctlmsr(); |