[PATCH 5.17 145/219] scsi: target: tcmu: Fix possible page UAF

Greg Kroah-Hartman
2022-04-18T12:32:30Z

From: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>

[ Upstream commit a6968f7a367f128d120447360734344d5a3d5336 ]

tcmu_try_get_data_page() looks up pages under cmdr_lock, but it does not
take refcount properly and just returns page pointer. When
tcmu_try_get_data_page() returns, the returned page may have been freed by
tcmu_blocks_release().

We need to get_page() under cmdr_lock to avoid concurrent
tcmu_blocks_release().

Link: https://lore.kernel.org/r/20220311132206.24515-1-xiaoguang.wang@linux.alibaba.com
Reviewed-by: Bodo Stroesser <bostroesser@gmail.com>
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/target/target_core_user.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
index 7b2a89a67cdb..06a5c4086551 100644
--- a/drivers/target/target_core_user.c
+++ b/drivers/target/target_core_user.c
@@ -1820,6 +1820,7 @@ static struct page *tcmu_try_get_data_page(struct tcmu_dev *udev, uint32_t dpi)
mutex_lock(&udev->cmdr_lock);
page = xa_load(&udev->data_pages, dpi);
if (likely(page)) {
+ get_page(page);
mutex_unlock(&udev->cmdr_lock);
return page;
}
@@ -1876,6 +1877,7 @@ static vm_fault_t tcmu_vma_fault(struct vm_fault *vmf)
/* For the vmalloc()ed cmd area pages */
addr = (void *)(unsigned long)info->mem[mi].addr + offset;
page = vmalloc_to_page(addr);
+ get_page(page);
} else {
uint32_t dpi;

@@ -1886,7 +1888,6 @@ static vm_fault_t tcmu_vma_fault(struct vm_fault *vmf)
return VM_FAULT_SIGBUS;
}

- get_page(page);
vmf->page = page;
return 0;
}
--
2.35.1