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ptrace: Move setting/clearing ptrace_message into ptrace_stop

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Today ptrace_message is easy to overlook as it not a core part of
ptrace_stop.  It has been overlooked so much that there are places
that set ptrace_message and don't clear it, and places that never set
it.  So if you get an unlucky sequence of events the ptracer may be
able to read a ptrace_message that does not apply to the current
ptrace stop.

Move setting of ptrace_message into ptrace_stop so that it always gets
set before the stop, and always gets cleared after the stop.  This
prevents non-sense from being reported to userspace and makes
ptrace_message more visible in the ptrace helper functions so that
kernel developers can see it.

Link: https://lkml.kernel.org/r/87bky67qfv.fsf_-_@email.froward.int.ebiederm.org
Acked-by: Oleg Nesterov <oleg@redhat.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Eric W. Biederman 2022-01-27 12:15:32 -06:00
parent 355f841a3f
commit 336d4b814b
3 changed files with 16 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

9
include/linux/ptrace.h
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@ -60,7 +60,7 @@ extern int ptrace_writedata(struct task_struct *tsk, char __user *src, unsigned
extern void ptrace_disable(struct task_struct *);
extern int ptrace_request(struct task_struct *child, long request,
unsigned long addr, unsigned long data);
extern void ptrace_notify(int exit_code);
extern void ptrace_notify(int exit_code, unsigned long message);
extern void __ptrace_link(struct task_struct *child,
struct task_struct *new_parent,
const struct cred *ptracer_cred);
@ -155,8 +155,7 @@ static inline bool ptrace_event_enabled(struct task_struct *task, int event)
static inline void ptrace_event(int event, unsigned long message)
{
if (unlikely(ptrace_event_enabled(current, event))) {
current->ptrace_message = message;
ptrace_notify((event << 8) | SIGTRAP);
ptrace_notify((event << 8) | SIGTRAP, message);
} else if (event == PTRACE_EVENT_EXEC) {
/* legacy EXEC report via SIGTRAP */
if ((current->ptrace & (PT_PTRACED|PT_SEIZED)) == PT_PTRACED)
@ -424,8 +423,7 @@ static inline int ptrace_report_syscall(unsigned long message)
if (!(ptrace & PT_PTRACED))
return 0;
current->ptrace_message = message;
ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0));
ptrace_notify(SIGTRAP | ((ptrace & PT_TRACESYSGOOD) ? 0x80 : 0), message);
/*
* this isn't the same as continuing with a signal, but it will do
@ -437,7 +435,6 @@ static inline int ptrace_report_syscall(unsigned long message)
current->exit_code = 0;
}
current->ptrace_message = 0;
return fatal_signal_pending(current);
}