Messages in this thread Patch in this message | | | Date | Thu, 27 Oct 2016 08:30:11 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH 2/4] x86/unwind: ensure stack grows down |
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* 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 | 36 ++++++++++++++++++++++++++++++++---- > 1 file changed, 32 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c > index 9be9a8f..0d8d2f2 100644 > --- a/arch/x86/kernel/unwind_frame.c > +++ b/arch/x86/kernel/unwind_frame.c > @@ -24,6 +24,15 @@ 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));
Unnecessary parentheses.
> + > + return sizeof(*regs); > +} > + > static bool is_last_task_frame(struct unwind_state *state) > { > unsigned long bp = (unsigned long)state->bp; > @@ -71,6 +80,7 @@ bool unwind_next_frame(struct unwind_state *state) > struct pt_regs *regs; > unsigned long *next_bp, *next_frame; > size_t next_len; > + enum stack_type prev_type = state->stack_info.type; > > if (unwind_done(state)) > return false; > @@ -134,6 +144,18 @@ bool unwind_next_frame(struct unwind_state *state) > goto bad_address; > } > > + /* make sure it only unwinds up and doesn't overlap the last frame */
Please capitalize comments - and if the comment refers to a control block please also add ':', i.e. something like:
/* Make sure it only unwinds up and doesn't overlap the last frame: */
This also applies to other places in this patch series.
> + if (state->stack_info.type == prev_type) { > + if (state->regs && > + (void *)next_frame < (void *)state->regs + > + regs_size(state->regs))
No line breaks that make the code worse please.
> + goto bad_address; > + > + if (state->bp && > + (void *)next_frame < (void *)state->bp + FRAME_HEADER_SIZE)
Ditto.
> + goto bad_address; > + } > + > /* move to the next frame */ > if (regs) { > state->regs = regs; > @@ -146,10 +168,16 @@ bool unwind_next_frame(struct unwind_state *state) > return true; > > bad_address: > - printk_deferred_once(KERN_WARNING > - "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", > - state->bp, state->task->comm, > - state->task->pid, next_bp); > + if (state->regs) > + printk_deferred_once(KERN_WARNING > + "WARNING: kernel stack regs at %p in %s:%d has bad 'bp' value %p\n", > + state->regs, state->task->comm, > + state->task->pid, next_frame); > + else > + printk_deferred_once(KERN_WARNING > + "WARNING: kernel stack frame pointer at %p in %s:%d has bad value %p\n", > + state->bp, state->task->comm, > + state->task->pid, next_frame);
Multi-line statements should have curly braces.
Thanks,
Ingo
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