[PATCH 6.6 093/301] swiotlb: initialise restricted pool list_head when SWIOTLB_DYNAMIC=y

Greg Kroah-Hartman
2024-05-14T11:07:46Z

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);

--
2.43.0