| Message ID | 20220429214837.386518-6-ebiederm@xmission.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere, archived |
| Headers | show |
| Series | ptrace: cleaning up ptrace_stop | expand |
On 04/29, Eric W. Biederman wrote: > > Call send_sig_info in PTRACE_KILL instead of ptrace_resume. Calling > ptrace_resume is not safe to call if the task has not been stopped > with ptrace_freeze_traced. Oh, I was never, never able to understand why do we have PTRACE_KILL and what should it actually do. I suggested many times to simply remove it but OK, we probably can't do this. > --- a/kernel/ptrace.c > +++ b/kernel/ptrace.c > @@ -1238,7 +1238,7 @@ int ptrace_request(struct task_struct *child, long request, > case PTRACE_KILL: > if (child->exit_state) /* already dead */ > return 0; > - return ptrace_resume(child, request, SIGKILL); > + return send_sig_info(SIGKILL, SEND_SIG_NOINFO, child); Note that currently ptrace(PTRACE_KILL) can never fail (yes, yes, it is unsafe), but send_sig_info() can. If we do not remove PTRACE_KILL, then I'd suggest case PTRACE_KILL: if (!child->exit_state) send_sig_info(SIGKILL); return 0; to make this change a bit more compatible. Also, please remove the note about PTRACE_KILL in set_task_blockstep(). Oleg.
Oleg Nesterov <oleg@redhat.com> writes: > On 04/29, Eric W. Biederman wrote: >> >> Call send_sig_info in PTRACE_KILL instead of ptrace_resume. Calling >> ptrace_resume is not safe to call if the task has not been stopped >> with ptrace_freeze_traced. > > Oh, I was never, never able to understand why do we have PTRACE_KILL > and what should it actually do. > > I suggested many times to simply remove it but OK, we probably can't > do this. I thought I remembered you suggesting fixing it in some other way. I took at quick look in codesearch.debian.net and PTRACE_KILL is definitely in use. I find uses in gcc-10, firefox-esr_91.8, llvm_toolchain, qtwebengine. At which point I stopped looking. >> --- a/kernel/ptrace.c >> +++ b/kernel/ptrace.c >> @@ -1238,7 +1238,7 @@ int ptrace_request(struct task_struct *child, long request, >> case PTRACE_KILL: >> if (child->exit_state) /* already dead */ >> return 0; >> - return ptrace_resume(child, request, SIGKILL); >> + return send_sig_info(SIGKILL, SEND_SIG_NOINFO, child); > > Note that currently ptrace(PTRACE_KILL) can never fail (yes, yes, it > is unsafe), but send_sig_info() can. If we do not remove PTRACE_KILL, > then I'd suggest > > case PTRACE_KILL: > if (!child->exit_state) > send_sig_info(SIGKILL); > return 0; > > to make this change a bit more compatible. Quite. The only failure I can find from send_sig_info is if lock_task_sighand fails and PTRACE_KILL is deliberately ignoring errors when the target task has exited. case PTRACE_KILL: send_sig_info(SIGKILL); return 0; I think that should suffice. > Also, please remove the note about PTRACE_KILL in > set_task_blockstep(). Good catch, thank you. Eric
diff --git a/kernel/ptrace.c b/kernel/ptrace.c index ccc4b465775b..43da5764b6f3 100644 --- a/kernel/ptrace.c +++ b/kernel/ptrace.c @@ -1238,7 +1238,7 @@ int ptrace_request(struct task_struct *child, long request, case PTRACE_KILL: if (child->exit_state) /* already dead */ return 0; - return ptrace_resume(child, request, SIGKILL); + return send_sig_info(SIGKILL, SEND_SIG_NOINFO, child); #ifdef CONFIG_HAVE_ARCH_TRACEHOOK case PTRACE_GETREGSET:
Call send_sig_info in PTRACE_KILL instead of ptrace_resume. Calling ptrace_resume is not safe to call if the task has not been stopped with ptrace_freeze_traced. Cc: stable@vger.kernel.org Reported-by: Al Viro <viro@zeniv.linux.org.uk> Suggested-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com> --- kernel/ptrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)