diff options
| author | Tejun Heo <tj@kernel.org> | 2014-07-03 15:43:15 -0400 |
|---|---|---|
| committer | Willy Tarreau <w@1wt.eu> | 2014-11-23 10:55:37 +0100 |
| commit | a3b45048ba450a3f94e5f1a8c616a0925a0da07a (patch) | |
| tree | 551999b9fa6b274d960c168525c4920e49d2fe16 /include | |
| parent | 883f30e7d98d97d704df38cd2972a33be852f23a (diff) | |
ptrace,x86: force IRET path after a ptrace_stop()
[ Upstream commit b9cd18de4db3c9ffa7e17b0dc0ca99ed5aa4d43a ]
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>
[wt: fixes CVE-2014-4699]
Signed-off-by: Willy Tarreau <w@1wt.eu>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/ptrace.h | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/include/linux/ptrace.h b/include/linux/ptrace.h index 7456d7d87a19..486d27fa0308 100644 --- a/include/linux/ptrace.h +++ b/include/linux/ptrace.h @@ -292,6 +292,9 @@ static inline void user_enable_block_step(struct task_struct *task) * 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 |