6.6-stable review patch. If anyone has any objections, please let me know.
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From: Will Deacon will@kernel.org
[ Upstream commit 75961ffb5cb3e5196f19cae7683f35cc88b50800 ]
Using restricted DMA pools (CONFIG_DMA_RESTRICTED_POOL=y) in conjunction with dynamic SWIOTLB (CONFIG_SWIOTLB_DYNAMIC=y) leads to the following crash when initialising the restricted pools at boot-time:
| Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 | Internal error: Oops: 0000000096000005 [#1] PREEMPT SMP | pc : rmem_swiotlb_device_init+0xfc/0x1ec | lr : rmem_swiotlb_device_init+0xf0/0x1ec | Call trace: | rmem_swiotlb_device_init+0xfc/0x1ec | of_reserved_mem_device_init_by_idx+0x18c/0x238 | of_dma_configure_id+0x31c/0x33c | platform_dma_configure+0x34/0x80
faddr2line reveals that the crash is in the list validation code:
include/linux/list.h:83 include/linux/rculist.h:79 include/linux/rculist.h:106 kernel/dma/swiotlb.c:306 kernel/dma/swiotlb.c:1695
because add_mem_pool() is trying to list_add_rcu() to a NULL 'mem->pools'.
Fix the crash by initialising the 'mem->pools' list_head in rmem_swiotlb_device_init() before calling add_mem_pool().
Reported-by: Nikita Ioffe ioffe@google.com Tested-by: Nikita Ioffe ioffe@google.com Fixes: 1aaa736815eb ("swiotlb: allocate a new memory pool when existing pools are full") Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Christoph Hellwig hch@lst.de Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/dma/swiotlb.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index 675ae318f74f8..a7d5fb473b324 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -1692,6 +1692,7 @@ static int rmem_swiotlb_device_init(struct reserved_mem *rmem, mem->for_alloc = true; #ifdef CONFIG_SWIOTLB_DYNAMIC spin_lock_init(&mem->lock); + INIT_LIST_HEAD_RCU(&mem->pools); #endif add_mem_pool(mem, pool);