Re: [PATCH for-next v2] RDMA/rxe: Fix mr->map double free

[Yanjun Zhu <yanjun.zhu@linux.dev>]

在 2022/10/30 11:04, Li Zhijian 写道:
> rxe_mr_cleanup() which tries to free mr->map again will be called
> when rxe_mr_init_user() fails.
> 
> [43895.939883] CPU: 0 PID: 4917 Comm: rdma_flush_serv Kdump: loaded Not tainted 6.1.0-rc1-roce-flush+ #25
> [43895.942341] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.org 04/01/2014
> [43895.945208] Call Trace:
> [43895.946130]  <TASK>
> [43895.946931]  dump_stack_lvl+0x45/0x5d
> [43895.948049]  panic+0x19e/0x349
> [43895.949010]  ? panic_print_sys_info.part.0+0x77/0x77
> [43895.950356]  ? asm_sysvec_apic_timer_interrupt+0x16/0x20
> [43895.952589]  ? preempt_count_sub+0x14/0xc0
> [43895.953809]  end_report.part.0+0x54/0x7c
> [43895.954993]  ? rxe_mr_cleanup+0x9d/0xf0 [rdma_rxe]
> [43895.956406]  kasan_report.cold+0xa/0xf
> [43895.957668]  ? rxe_mr_cleanup+0x9d/0xf0 [rdma_rxe]
> [43895.959090]  rxe_mr_cleanup+0x9d/0xf0 [rdma_rxe]
> [43895.960502]  __rxe_cleanup+0x10a/0x1e0 [rdma_rxe]
> [43895.961983]  rxe_reg_user_mr+0xb7/0xd0 [rdma_rxe]
> [43895.963456]  ib_uverbs_reg_mr+0x26a/0x480 [ib_uverbs]
> [43895.964921]  ? __lock_acquire+0x876/0x31e0
> [43895.966182]  ? ib_uverbs_ex_create_wq+0x630/0x630 [ib_uverbs]
> [43895.967739]  ? uverbs_fill_udata+0x1c6/0x330 [ib_uverbs]
> [43895.969204]  ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x1a2/0x250 [ib_uverbs]
> [43895.971126]  ? ib_uverbs_handler_UVERBS_METHOD_QUERY_CONTEXT+0x1a0/0x1a0 [ib_uverbs]
> [43895.973094]  ? ib_uverbs_handler_UVERBS_METHOD_QUERY_CONTEXT+0x1a0/0x1a0 [ib_uverbs]
> [43895.975096]  ? uverbs_fill_udata+0x25f/0x330 [ib_uverbs]
> [43895.976466]  ib_uverbs_cmd_verbs+0x1397/0x15a0 [ib_uverbs]
> [43895.977930]  ? ib_uverbs_handler_UVERBS_METHOD_QUERY_CONTEXT+0x1a0/0x1a0 [ib_uverbs]
> [43895.979937]  ? uverbs_fill_udata+0x330/0x330 [ib_uverbs]
> 
> This issue was fistrly exposed since
> commit: b18c7da63fcb ("RDMA/rxe: Fix memory leak in error path code")
> and then we fixed it in
> commit: 8ff5f5d9d8cf ("RDMA/rxe: Prevent double freeing rxe_map_set()")
> but this fix was reverted together at last by
> commit: 1e75550648da (Revert "RDMA/rxe: Create duplicate mapping tables for FMRs")
> 
> Fixes: 1e75550648da (Revert "RDMA/rxe: Create duplicate mapping tables for FMRs")
> Signed-off-by: Li Zhijian <lizhijian@fujitsu.com>
> ---
>   drivers/infiniband/sw/rxe/rxe_mr.c | 9 ++-------
>   1 file changed, 2 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/infiniband/sw/rxe/rxe_mr.c b/drivers/infiniband/sw/rxe/rxe_mr.c
> index d4f10c2d1aa7..7c99d1591580 100644
> --- a/drivers/infiniband/sw/rxe/rxe_mr.c
> +++ b/drivers/infiniband/sw/rxe/rxe_mr.c
> @@ -99,6 +99,7 @@ static int rxe_mr_alloc(struct rxe_mr *mr, int num_buf)
>   		kfree(mr->map[i]);
>   
>   	kfree(mr->map);
> +	mr->map = NULL;
>   err1:
>   	return -ENOMEM;
>   }
> @@ -122,7 +123,6 @@ int rxe_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
>   	int			num_buf;
>   	void			*vaddr;
>   	int err;
> -	int i;
>   
>   	umem = ib_umem_get(&rxe->ib_dev, start, length, access);
>   	if (IS_ERR(umem)) {
> @@ -163,9 +163,8 @@ int rxe_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
>   				pr_warn("%s: Unable to get virtual address\n",
>   						__func__);
>   				err = -ENOMEM;
> -				goto err_cleanup_map;
> +				goto err_release_umem;

This call trace results from page_address's returning NULL, then goto 
err_cleanup_map where mr->map[i] and mr->map are freed.

And finally rxe_reg_user_mr gets an error from rxe_mr_init_user, the 
function rxe_mr_cleanup is called to handle mr to free mr->map[i] and 
mr->map again.

So mr->map[i] and mr->map are double freed.

As such, this commit is reasonable.

But why page_address will return NULL?

Zhu Yanjun

>   			}
> -
>   			buf->addr = (uintptr_t)vaddr;
>   			buf->size = PAGE_SIZE;
>   			num_buf++;
> @@ -182,10 +181,6 @@ int rxe_mr_init_user(struct rxe_dev *rxe, u64 start, u64 length, u64 iova,
>   
>   	return 0;
>   
> -err_cleanup_map:
> -	for (i = 0; i < mr->num_map; i++)
> -		kfree(mr->map[i]);
> -	kfree(mr->map);
>   err_release_umem:
>   	ib_umem_release(umem);
>   err_out: