* Josh Poimboeuf <jpoim...@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 <jpoim...@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
