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authorTejun Heo <tj@kernel.org>2014-07-03 15:43:15 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-07-03 17:27:23 -0700
commitb9cd18de4db3c9ffa7e17b0dc0ca99ed5aa4d43a (patch)
treee8bee2447217ee19371f86e7b24e6d12ecb58234 /include
parent5170a3b24a9141e2349a3420448743b7c68f2223 (diff)
ptrace,x86: force IRET path after a ptrace_stop()
The 'sysret' fastpath does not correctly restore even all regular registers, much less any segment registers or reflags values. That is very much part of why it's faster than 'iret'. Normally that isn't a problem, because the normal ptrace() interface catches the process using the signal handler infrastructure, which always returns with an iret. However, some paths can get caught using ptrace_event() instead of the signal path, and for those we need to make sure that we aren't going to return to user space using 'sysret'. Otherwise the modifications that may have been done to the register set by the tracer wouldn't necessarily take effect. Fix it by forcing IRET path by setting TIF_NOTIFY_RESUME from arch_ptrace_stop_needed() which is invoked from ptrace_stop(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Andy Lutomirski <luto@amacapital.net> Acked-by: Oleg Nesterov <oleg@redhat.com> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
-rw-r--r--include/linux/ptrace.h3
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h
index 077904c8b70d..cc79eff4a1ad 100644
--- a/include/linux/ptrace.h
+++ b/include/linux/ptrace.h
@@ -334,6 +334,9 @@ static inline void user_single_step_siginfo(struct task_struct *tsk,
* calling arch_ptrace_stop() when it would be superfluous. For example,
* if the thread has not been back to user mode since the last stop, the
* thread state might indicate that nothing needs to be done.
+ *
+ * This is guaranteed to be invoked once before a task stops for ptrace and
+ * may include arch-specific operations necessary prior to a ptrace stop.
*/
#define arch_ptrace_stop_needed(code, info) (0)
#endif

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