linux-kernel - Re: [PATCH v2] locking/lockdep: Fix buffer overrun problem in stack

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Message-ID: <11cdb8cb-579c-0655-0f42-625680b8249f@acm.org>
Date:   Fri, 20 Dec 2019 07:23:30 -0800
From:   Bart Van Assche <bvanassche@....org>
To:     Waiman Long <longman@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Will Deacon <will.deacon@....com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] locking/lockdep: Fix buffer overrun problem in
 stack_trace[]

On 2019-12-20 05:51, Waiman Long wrote:
> If the lockdep code is really running out of the stack_trace entries,
> it is likely that buffer overrun can happen and the data immediately
> after stack_trace[] will be corrupted.
> 
> If there is less than LOCK_TRACE_SIZE_IN_LONGS entries left before
> the call to save_trace(), the max_entries computation will leave it
> with a very large positive number because of its unsigned nature. The
> subsequent call to stack_trace_save() will then corrupt the data after
> stack_trace[]. Fix that by changing max_entries to a signed integer
> and check for negative value before calling stack_trace_save().

Reviewed-by: Bart Van Assche <bvanassche@....org>