Messages in this thread | | | From | Andy Lutomirski <> | Date | Sun, 14 Aug 2016 00:56:40 -0700 | Subject | Re: [PATCH v3 48/51] x86/unwind: warn if stack grows up |
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On Fri, Aug 12, 2016 at 7:29 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > Add a sanity check to ensure the stack only grows down, and print a > warning if the check fails. > > Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> > --- > arch/x86/kernel/unwind_frame.c | 26 ++++++++++++++++++++++++-- > 1 file changed, 24 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c > index 5496462..f21b7ef 100644 > --- a/arch/x86/kernel/unwind_frame.c > +++ b/arch/x86/kernel/unwind_frame.c > @@ -32,6 +32,15 @@ unsigned long unwind_get_return_address(struct unwind_state *state) > } > EXPORT_SYMBOL_GPL(unwind_get_return_address); > > +static size_t regs_size(struct pt_regs *regs) > +{ > + /* x86_32 regs from kernel mode are two words shorter */ > + if (IS_ENABLED(CONFIG_X86_32) && !user_mode(regs)) > + return sizeof(*regs) - (2*sizeof(long)); > + > + return sizeof(*regs); > +} > + > static bool is_last_task_frame(struct unwind_state *state) > { > unsigned long bp = (unsigned long)state->bp; > @@ -85,6 +94,7 @@ bool unwind_next_frame(struct unwind_state *state) > struct pt_regs *regs; > unsigned long *next_bp, *next_sp; > size_t next_len; > + enum stack_type prev_type = state->stack_info.type; > > if (unwind_done(state)) > return false; > @@ -140,6 +150,18 @@ bool unwind_next_frame(struct unwind_state *state) > if (!update_stack_state(state, next_sp, next_len)) > goto bad_address; > > + /* make sure it only unwinds up and doesn't overlap the last frame */ > + if (state->stack_info.type == prev_type) { > + if (state->regs && > + (void *)next_sp < (void *)state->regs + > + regs_size(state->regs)) > + goto bad_address; > + > + if (state->bp && > + (void *)next_sp < (void *)state->bp + FRAME_HEADER_SIZE) > + goto bad_address; > + } > +
Maybe this is obvious in context, but does something prevent this error from firing if the stack switched? That is:
pushq $rbp movq $rsp, $rbp ... movq [irq stack], $rsp <- rsp and rbp have no particular relationship right now.
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