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lib: cpu_rmap: Avoid use after free on rmap->obj array entries
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[ Upstream commit 4e0473f ]

When calling irq_set_affinity_notifier() with NULL at the notify
argument, it will cause freeing of the glue pointer in the
corresponding array entry but will leave the pointer in the array. A
subsequent call to free_irq_cpu_rmap() will try to free this entry again
leading to possible use after free.

Fix that by setting NULL to the array entry and checking that we have
non-zero at the array entry when iterating over the array in
free_irq_cpu_rmap().

The current code does not suffer from this since there are no cases
where irq_set_affinity_notifier(irq, NULL) (note the NULL passed for the
notify arg) is called, followed by a call to free_irq_cpu_rmap() so we
don't hit and issue. Subsequent patches in this series excersize this
flow, hence the required fix.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Eli Cohen <elic@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
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elic307i authored and gregkh committed May 24, 2023
1 parent a7a4def commit c9115f4
Showing 1 changed file with 4 additions and 1 deletion.
5 changes: 4 additions & 1 deletion lib/cpu_rmap.c
Expand Up @@ -232,7 +232,8 @@ void free_irq_cpu_rmap(struct cpu_rmap *rmap)

for (index = 0; index < rmap->used; index++) {
glue = rmap->obj[index];
irq_set_affinity_notifier(glue->notify.irq, NULL);
if (glue)
irq_set_affinity_notifier(glue->notify.irq, NULL);
}

cpu_rmap_put(rmap);
Expand Down Expand Up @@ -268,6 +269,7 @@ static void irq_cpu_rmap_release(struct kref *ref)
container_of(ref, struct irq_glue, notify.kref);

cpu_rmap_put(glue->rmap);
glue->rmap->obj[glue->index] = NULL;
kfree(glue);
}

Expand Down Expand Up @@ -297,6 +299,7 @@ int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq)
rc = irq_set_affinity_notifier(irq, &glue->notify);
if (rc) {
cpu_rmap_put(glue->rmap);
rmap->obj[glue->index] = NULL;
kfree(glue);
}
return rc;
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