From: Vitaly Kuznetsov Date: Fri, 19 Mar 2021 11:18:23 +0000 (+0100) Subject: genirq/matrix: Prevent allocation counter corruption X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=c93a5e20c3c2dabef8ea360a3d3f18c6f68233ab;p=linux.git genirq/matrix: Prevent allocation counter corruption When irq_matrix_free() is called for an unallocated vector the managed_allocated and total_allocated counters get out of sync with the real state of the matrix. Later, when the last interrupt is freed, these counters will underflow resulting in UINTMAX because the counters are unsigned. While this is certainly a problem of the calling code, this can be catched in the allocator by checking the allocation bit for the to be freed vector which simplifies debugging. An example of the problem described above: https://lore.kernel.org/lkml/20210318192819.636943062@linutronix.de/ Add the missing sanity check and emit a warning when it triggers. Suggested-by: Thomas Gleixner Signed-off-by: Vitaly Kuznetsov Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210319111823.1105248-1-vkuznets@redhat.com --- diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c index 6f8b1d171cdc8..578596e41cb60 100644 --- a/kernel/irq/matrix.c +++ b/kernel/irq/matrix.c @@ -422,7 +422,9 @@ void irq_matrix_free(struct irq_matrix *m, unsigned int cpu, if (WARN_ON_ONCE(bit < m->alloc_start || bit >= m->alloc_end)) return; - clear_bit(bit, cm->alloc_map); + if (WARN_ON_ONCE(!test_and_clear_bit(bit, cm->alloc_map))) + return; + cm->allocated--; if(managed) cm->managed_allocated--;