RE: [PATCH v2] mlx5: fix init stage error handling to avoid double free of same QP and UAF

[Qing Huang]

> -----Original Message-----
> From: George Kennedy <george.kennedy@xxxxxxxxxx>
> Sent: Tuesday, October 24, 2023 11:02 AM
> To: leon@xxxxxxxxxx; jgg@xxxxxxxx; sd@xxxxxxxxxxxxxxx; linux-
> rdma@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Cc: George Kennedy <george.kennedy@xxxxxxxxxx>; Tom Hromatka
> <tom.hromatka@xxxxxxxxxx>; Harshit Mogalapalli
> <harshit.m.mogalapalli@xxxxxxxxxx>
> Subject: [PATCH v2] mlx5: fix init stage error handling to avoid double free of
> same QP and UAF
> 
> In the unlikely event that workqueue allocation fails and returns NULL in
> mlx5_mkey_cache_init(), delete the call to
> mlx5r_umr_resource_cleanup() (which frees the QP) in
> mlx5_ib_stage_post_ib_reg_umr_init().  This will avoid attempted double free of
> the same QP when __mlx5_ib_add() does its cleanup.
> 


Hi George,

There seems no cleanup function defined for this stage:

        STAGE_CREATE(MLX5_IB_STAGE_POST_IB_REG_UMR,
                     mlx5_ib_stage_post_ib_reg_umr_init,
                     NULL),

Do you know where __mlx5_ib_add() does the double free call after the allocation failure?

Regards,
Qing

> Syzkaller reported a UAF in ib_destroy_qp_user
> 
> workqueue: Failed to create a rescuer kthread for wq "mkey_cache": -EINTR
> infiniband mlx5_0: mlx5_mkey_cache_init:981:(pid 1642):
> failed to create work queue
> infiniband mlx5_0: mlx5_ib_stage_post_ib_reg_umr_init:4075:(pid 1642):
> mr cache init failed -12
> ==================================================================
> BUG: KASAN: slab-use-after-free in ib_destroy_qp_user
> (drivers/infiniband/core/verbs.c:2073)
> Read of size 8 at addr ffff88810da310a8 by task repro_upstream/1642
> 
> Call Trace:
> <TASK>
> kasan_report (mm/kasan/report.c:590)
> ib_destroy_qp_user (drivers/infiniband/core/verbs.c:2073)
> mlx5r_umr_resource_cleanup (drivers/infiniband/hw/mlx5/umr.c:198)
> __mlx5_ib_add (drivers/infiniband/hw/mlx5/main.c:4178)
> mlx5r_probe (drivers/infiniband/hw/mlx5/main.c:4402)
> ...
> </TASK>
> 
> Allocated by task 1642:
> __kmalloc (./include/linux/kasan.h:198 mm/slab_common.c:1026
> mm/slab_common.c:1039)
> create_qp (./include/linux/slab.h:603 ./include/linux/slab.h:720
> ./include/rdma/ib_verbs.h:2795 drivers/infiniband/core/verbs.c:1209)
> ib_create_qp_kernel (drivers/infiniband/core/verbs.c:1347)
> mlx5r_umr_resource_init (drivers/infiniband/hw/mlx5/umr.c:164)
> mlx5_ib_stage_post_ib_reg_umr_init (drivers/infiniband/hw/mlx5/main.c:4070)
> __mlx5_ib_add (drivers/infiniband/hw/mlx5/main.c:4168)
> mlx5r_probe (drivers/infiniband/hw/mlx5/main.c:4402)
> ...
> 
> Freed by task 1642:
> __kmem_cache_free (mm/slub.c:1826 mm/slub.c:3809 mm/slub.c:3822)
> ib_destroy_qp_user (drivers/infiniband/core/verbs.c:2112)
> mlx5r_umr_resource_cleanup (drivers/infiniband/hw/mlx5/umr.c:198)
> mlx5_ib_stage_post_ib_reg_umr_init (drivers/infiniband/hw/mlx5/main.c:4076
> drivers/infiniband/hw/mlx5/main.c:4065)
> __mlx5_ib_add (drivers/infiniband/hw/mlx5/main.c:4168)
> mlx5r_probe (drivers/infiniband/hw/mlx5/main.c:4402)
> ...
> 
> The buggy address belongs to the object at ffff88810da31000 which belongs to
> the cache kmalloc-2k of size 2048 The buggy address is located 168 bytes inside
> of freed 2048-byte region [ffff88810da31000, ffff88810da31800)
> 
> The buggy address belongs to the physical page:
> page:000000003b5e469d refcount:1 mapcount:0 mapping:0000000000000000
> index:0x0 pfn:0x10da30
> head:000000003b5e469d order:3 entire_mapcount:0 nr_pages_mapped:0
> pincount:0
> flags: 0x17ffffc0000840(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> page_type: 0xffffffff()
> raw: 0017ffffc0000840 ffff888100042f00 ffffea0004180800
> dead000000000002
> raw: 0000000000000000 0000000000080008 00000001ffffffff
> 0000000000000000 page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
> ffff88810da30f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ffff88810da31000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff88810da31080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> 			      ^
> ffff88810da31100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff88810da31180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> Disabling lock debugging due to kernel taint
> 
> Fixes: 04876c12c19e ("RDMA/mlx5: Move init and cleanup of UMR to umr.c")
> Reported-by: syzkaller <syzkaller@xxxxxxxxxxxxxxxx>
> Suggested-by: Leon Romanovsky <leon@xxxxxxxxxx>
> Signed-off-by: George Kennedy <george.kennedy@xxxxxxxxxx>
> ---
> v2: went with fix suggested by: Leon Romanovsky <leon@xxxxxxxxxx>
> 
>  drivers/infiniband/hw/mlx5/main.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/drivers/infiniband/hw/mlx5/main.c
> b/drivers/infiniband/hw/mlx5/main.c
> index 555629b7..5d963ab 100644
> --- a/drivers/infiniband/hw/mlx5/main.c
> +++ b/drivers/infiniband/hw/mlx5/main.c
> @@ -4071,10 +4071,8 @@ static int
> mlx5_ib_stage_post_ib_reg_umr_init(struct mlx5_ib_dev *dev)
>  		return ret;
> 
>  	ret = mlx5_mkey_cache_init(dev);
> -	if (ret) {
> +	if (ret)
>  		mlx5_ib_warn(dev, "mr cache init failed %d\n", ret);
> -		mlx5r_umr_resource_cleanup(dev);
> -	}
>  	return ret;
>  }
> 
> --
> 1.8.3.1