Re: [PATCH] objtool: Fix stack overflow in validate_branch()

[Josh Poimboeuf]

On Tue, Dec 02, 2025 at 05:20:22PM +0100, Ingo Molnar wrote:
> 
> * Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:
> 
> > On an allmodconfig kernel compiled with Clang, objtool is segfaulting in
> > drivers/scsi/qla2xxx/qla2xxx.o due to a stack overflow in
> > validate_branch().
> > 
> > Due in part to KASAN being enabled, the qla2xxx code has a large number
> > of conditional jumps, causing objtool to go quite deep in its recursion.
> > 
> > By far the biggest offender of stack usage is the recently added
> > 'prev_state' stack variable in validate_insn(), coming in at 328 bytes.
> 
> That's weird - how can a user-space tool run into stack 
> limits, are they set particularly conservatively?

On my Fedora system, "ulimit -s" is 8MB.  You'd think that would be
enough :-)

In this case, objtool had over 20,000 stack frames caused by recursively
following over 7,000(!) conditional jumps in a single function.

> In any case, applied to tip:objtool/urgent, thanks!

Looks good now, thanks for fixing that up!

-- 
Josh