From 60e6627f12a78203a093ca05b7bca15627747d81 Mon Sep 17 00:00:00 2001 From: Jann Horn Date: Fri, 6 Jul 2018 22:48:03 +0200 Subject: IB/mlx5: fix uaccess beyond "count" in debugfs read/write handlers In general, accessing userspace memory beyond the length of the supplied buffer in VFS read/write handlers can lead to both kernel memory corruption (via kernel_read()/kernel_write(), which can e.g. be triggered via sys_splice()) and privilege escalation inside userspace. In this case, the affected files are in debugfs (and should therefore only be accessible to root), and the read handlers check that *pos is zero (meaning that at least sys_splice() can't trigger kernel memory corruption). Because of the root requirement, this is not a security fix, but rather a cleanup. For the read handlers, fix it by using simple_read_from_buffer() instead of custom logic. Add min() calls to the write handlers. Fixes: 4a2da0b8c078 ("IB/mlx5: Add debug control parameters for congestion control") Fixes: e126ba97dba9 ("mlx5: Add driver for Mellanox Connect-IB adapters") Signed-off-by: Jann Horn Reviewed-by: Leon Romanovsky Signed-off-by: Jason Gunthorpe --- drivers/infiniband/hw/mlx5/cong.c | 9 +-------- 1 file changed, 1 insertion(+), 8 deletions(-) (limited to 'drivers/infiniband/hw/mlx5/cong.c') diff --git a/drivers/infiniband/hw/mlx5/cong.c b/drivers/infiniband/hw/mlx5/cong.c index 985fa2637390..7e4e358a4fd8 100644 --- a/drivers/infiniband/hw/mlx5/cong.c +++ b/drivers/infiniband/hw/mlx5/cong.c @@ -359,9 +359,6 @@ static ssize_t get_param(struct file *filp, char __user *buf, size_t count, int ret; char lbuf[11]; - if (*pos) - return 0; - ret = mlx5_ib_get_cc_params(param->dev, param->port_num, offset, &var); if (ret) return ret; @@ -370,11 +367,7 @@ static ssize_t get_param(struct file *filp, char __user *buf, size_t count, if (ret < 0) return ret; - if (copy_to_user(buf, lbuf, ret)) - return -EFAULT; - - *pos += ret; - return ret; + return simple_read_from_buffer(buf, count, pos, lbuf, ret); } static const struct file_operations dbg_cc_fops = { -- cgit v1.2.3