diff options
| author | Josh Poimboeuf <jpoimboe@redhat.com> | 2016-08-18 10:59:06 -0500 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2016-10-16 17:36:15 +0200 |
| commit | 63f9190b09dd9980e50ea01c81eb5a06b798d9e2 (patch) | |
| tree | b6adf49dbc5b52cc6a475b2847c0768dedcadc92 /arch | |
| parent | eba90a4c76b91db06c307035c06b20dbcb5fa487 (diff) | |
x86/dumpstack: Fix x86_32 kernel_stack_pointer() previous stack access
commit 72b4f6a5e903b071f2a7c4eb1418cbe4eefdc344 upstream.
On x86_32, when an interrupt happens from kernel space, SS and SP aren't
pushed and the existing stack is used. So pt_regs is effectively two
words shorter, and the previous stack pointer is normally the memory
after the shortened pt_regs, aka '®s->sp'.
But in the rare case where the interrupt hits right after the stack
pointer has been changed to point to an empty stack, like for example
when call_on_stack() is used, the address immediately after the
shortened pt_regs is no longer on the stack. In that case, instead of
'®s->sp', the previous stack pointer should be retrieved from the
beginning of the current stack page.
kernel_stack_pointer() wants to do that, but it forgets to dereference
the pointer. So instead of returning a pointer to the previous stack,
it returns a pointer to the beginning of the current stack.
Note that it's probably outside of kernel_stack_pointer()'s scope to be
switching stacks at all. The x86_64 version of this function doesn't do
it, and it would be better for the caller to do it if necessary. But
that's a patch for another day. This just fixes the original intent.
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 0788aa6a23cb ("x86: Prepare removal of previous_esp from i386 thread_info structure")
Link: http://lkml.kernel.org/r/472453d6e9f6a2d4ab16aaed4935f43117111566.1471535549.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/ptrace.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c index 558f50edebca..479a409ddac8 100644 --- a/arch/x86/kernel/ptrace.c +++ b/arch/x86/kernel/ptrace.c @@ -188,8 +188,8 @@ unsigned long kernel_stack_pointer(struct pt_regs *regs) return sp; prev_esp = (u32 *)(context); - if (prev_esp) - return (unsigned long)prev_esp; + if (*prev_esp) + return (unsigned long)*prev_esp; return (unsigned long)regs; } |