genirq/matrix: Prevent allocation counter corruption

BugLink: https://bugs.launchpad.net/bugs/1928857
[ Upstream commit c93a5e20c3c2dabef8ea360a3d3f18c6f68233ab ]

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 <tglx@linutronix.de>
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20210319111823.1105248-1-vkuznets@redhat.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

diff --git a/kernel/irq/matrix.c b/kernel/irq/matrix.c
index 651a4ad6d711f82d8192d07a6b7616ef9337651f..8e586858bcf41f41d05b38ec1b08ea74a351d638 100644 (file)
--- a/kernel/irq/matrix.c
+++ b/kernel/irq/matrix.c
@@ -423,7 +423,9 @@ 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--;