From: Jann Horn jannh@google.com
[ Upstream commit 60e6627f12a78203a093ca05b7bca15627747d81 ]
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 jannh@google.com Reviewed-by: Leon Romanovsky leonro@mellanox.com Signed-off-by: Jason Gunthorpe jgg@mellanox.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com --- drivers/infiniband/hw/mlx5/cong.c | 9 +-------- drivers/infiniband/hw/mlx5/mr.c | 32 ++++++++----------------------- 2 files changed, 9 insertions(+), 32 deletions(-)
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 = { diff --git a/drivers/infiniband/hw/mlx5/mr.c b/drivers/infiniband/hw/mlx5/mr.c index 90a9c461cedc..308456d28afb 100644 --- a/drivers/infiniband/hw/mlx5/mr.c +++ b/drivers/infiniband/hw/mlx5/mr.c @@ -271,16 +271,16 @@ static ssize_t size_write(struct file *filp, const char __user *buf, { struct mlx5_cache_ent *ent = filp->private_data; struct mlx5_ib_dev *dev = ent->dev; - char lbuf[20]; + char lbuf[20] = {0}; u32 var; int err; int c;
- if (copy_from_user(lbuf, buf, sizeof(lbuf))) + count = min(count, sizeof(lbuf) - 1); + if (copy_from_user(lbuf, buf, count)) return -EFAULT;
c = order2idx(dev, ent->order); - lbuf[sizeof(lbuf) - 1] = 0;
if (sscanf(lbuf, "%u", &var) != 1) return -EINVAL; @@ -310,19 +310,11 @@ static ssize_t size_read(struct file *filp, char __user *buf, size_t count, char lbuf[20]; int err;
- if (*pos) - return 0; - err = snprintf(lbuf, sizeof(lbuf), "%d\n", ent->size); if (err < 0) return err;
- if (copy_to_user(buf, lbuf, err)) - return -EFAULT; - - *pos += err; - - return err; + return simple_read_from_buffer(buf, count, pos, lbuf, err); }
static const struct file_operations size_fops = { @@ -337,16 +329,16 @@ static ssize_t limit_write(struct file *filp, const char __user *buf, { struct mlx5_cache_ent *ent = filp->private_data; struct mlx5_ib_dev *dev = ent->dev; - char lbuf[20]; + char lbuf[20] = {0}; u32 var; int err; int c;
- if (copy_from_user(lbuf, buf, sizeof(lbuf))) + count = min(count, sizeof(lbuf) - 1); + if (copy_from_user(lbuf, buf, count)) return -EFAULT;
c = order2idx(dev, ent->order); - lbuf[sizeof(lbuf) - 1] = 0;
if (sscanf(lbuf, "%u", &var) != 1) return -EINVAL; @@ -372,19 +364,11 @@ static ssize_t limit_read(struct file *filp, char __user *buf, size_t count, char lbuf[20]; int err;
- if (*pos) - return 0; - err = snprintf(lbuf, sizeof(lbuf), "%d\n", ent->limit); if (err < 0) return err;
- if (copy_to_user(buf, lbuf, err)) - return -EFAULT; - - *pos += err; - - return err; + return simple_read_from_buffer(buf, count, pos, lbuf, err); }
static const struct file_operations limit_fops = {