Re: [PATCH rdma-rc v1] IB/core: Fix potential NULL pointer dereference in pkey cache

[Jason Gunthorpe <jgg@ziepe.ca>]

On Wed, May 06, 2020 at 08:32:13AM +0300, Leon Romanovsky wrote:
> From: Jack Morgenstein <jackm@dev.mellanox.co.il>
> 
> The IB core pkey cache is populated by procedure ib_cache_update().
> Initially, the pkey cache pointer is NULL. ib_cache_update allocates
> a buffer and populates it with the device's pkeys, via repeated calls
> to procedure ib_query_pkey().
> 
> If there is a failure in populating the pkey buffer via ib_query_pkey(),
> ib_cache_update does not replace the old pkey buffer cache with the
> updated one -- it leaves the old cache as is.
> 
> Since initially the pkey buffer cache is NULL, when calling
> ib_cache_update the first time, a failure in ib_query_pkey() will cause
> the pkey buffer cache pointer to remain NULL.
> 
> In this situation, any calls subsequent to ib_get_cached_pkey(),
> ib_find_cached_pkey(), or ib_find_cached_pkey_exact() will try to
> dereference the NULL pkey cache pointer, causing a kernel panic.
> 
> Fix this by checking the ib_cache_update() return value.
> 
> Fixes: 8faea9fd4a39 ("RDMA/cache: Move the cache per-port data into the main ib_port_data")
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Jack Morgenstein <jackm@dev.mellanox.co.il>
> Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
> ---
> Changelog:
> v1: I rewrote the patch to take care of ib_cache_update() return value.
> v0: https://lore.kernel.org/linux-rdma/20200426075811.129814-1-leon@kernel.org
> ---
>  drivers/infiniband/core/cache.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> --
> 2.26.2
> 
> diff --git a/drivers/infiniband/core/cache.c b/drivers/infiniband/core/cache.c
> index 717b798cddad..1cbebfa374a5 100644
> --- a/drivers/infiniband/core/cache.c
> +++ b/drivers/infiniband/core/cache.c
> @@ -1553,10 +1553,17 @@ int ib_cache_setup_one(struct ib_device *device)
>  	if (err)
>  		return err;
> 
> -	rdma_for_each_port (device, p)
> -		ib_cache_update(device, p, true);
> +	rdma_for_each_port (device, p) {
> +		err = ib_cache_update(device, p, true);
> +		if (err)
> +			goto out;
> +	}
> 
>  	return 0;
> +
> +out:
> +	ib_cache_release_one(device);
> +	return err;

ib_cache_release_once can be called only once, and it is always called
by ib_device_release(), it should not be called here

Jason