The following commit has been merged into the irq/urgent branch of tip:

Commit-ID: b84a8aba806261d2f759ccedf4a2a6a80a5e55ba Gitweb: https://git.kernel.org/tip/b84a8aba806261d2f759ccedf4a2a6a80a5e55ba Author: dicken.ding dicken.ding@mediatek.com AuthorDate: Fri, 24 May 2024 17:17:39 +08:00 Committer: Thomas Gleixner tglx@linutronix.de CommitterDate: Fri, 24 May 2024 12:49:35 +02:00

genirq/irqdesc: Prevent use-after-free in irq_find_at_or_after()

irq_find_at_or_after() dereferences the interrupt descriptor which is returned by mt_find() while neither holding sparse_irq_lock nor RCU read lock, which means the descriptor can be freed between mt_find() and the dereference:

CPU0 CPU1 desc = mt_find() delayed_free_desc(desc) irq_desc_get_irq(desc)

The use-after-free is reported by KASAN:

Call trace: irq_get_next_irq+0x58/0x84 show_stat+0x638/0x824 seq_read_iter+0x158/0x4ec proc_reg_read_iter+0x94/0x12c vfs_read+0x1e0/0x2c8

Freed by task 4471: slab_free_freelist_hook+0x174/0x1e0 __kmem_cache_free+0xa4/0x1dc kfree+0x64/0x128 irq_kobj_release+0x28/0x3c kobject_put+0xcc/0x1e0 delayed_free_desc+0x14/0x2c rcu_do_batch+0x214/0x720

Guard the access with a RCU read lock section.

Fixes: 721255b9826b ("genirq: Use a maple tree for interrupt descriptor management") Signed-off-by: dicken.ding dicken.ding@mediatek.com Signed-off-by: Thomas Gleixner tglx@linutronix.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240524091739.31611-1-dicken.ding@mediatek.com --- kernel/irq/irqdesc.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c index 88ac365..07e99c9 100644 --- a/kernel/irq/irqdesc.c +++ b/kernel/irq/irqdesc.c @@ -160,7 +160,10 @@ static int irq_find_free_area(unsigned int from, unsigned int cnt) static unsigned int irq_find_at_or_after(unsigned int offset) { unsigned long index = offset; - struct irq_desc *desc = mt_find(&sparse_irqs, &index, nr_irqs); + struct irq_desc *desc; + + guard(rcu)(); + desc = mt_find(&sparse_irqs, &index, nr_irqs);

return desc ? irq_desc_get_irq(desc) : nr_irqs; }