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net/mlx5: fix uaccess beyond "count" in debugfs read/write handlers

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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 check that *pos is zero (which prevents the
sys_splice() trick). Therefore, this is not a security fix, but rather a
small cleanup.

For the read handlers, fix it by using simple_read_from_buffer() instead of
custom logic.
For the write handler, add a check.

changed in v2:
 - also fix dbg_write()

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: Saeed Mahameed <saeedm@mellanox.com>
This commit is contained in:
Jann Horn 2018-07-06 22:18:09 +02:00 committed by Saeed Mahameed
parent b183ee27f5
commit 31e33a5b41
2 changed files with 9 additions and 41 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

28
drivers/net/ethernet/mellanox/mlx5/core/cmd.c
View File

@ -1032,7 +1032,10 @@ static ssize_t dbg_write(struct file *filp, const char __user *buf,
if (!dbg->in_msg || !dbg->out_msg)
return -ENOMEM;
if (copy_from_user(lbuf, buf, sizeof(lbuf)))
if (count < sizeof(lbuf) - 1)
return -EINVAL;
if (copy_from_user(lbuf, buf, sizeof(lbuf) - 1))
return -EFAULT;
lbuf[sizeof(lbuf) - 1] = 0;
@ -1236,21 +1239,12 @@ static ssize_t data_read(struct file *filp, char __user *buf, size_t count,
{
struct mlx5_core_dev *dev = filp->private_data;
struct mlx5_cmd_debug *dbg = &dev->cmd.dbg;
int copy;
if (*pos)
return 0;
if (!dbg->out_msg)
return -ENOMEM;
copy = min_t(int, count, dbg->outlen);
if (copy_to_user(buf, dbg->out_msg, copy))
return -EFAULT;
*pos += copy;
return copy;
return simple_read_from_buffer(buf, count, pos, dbg->out_msg,
dbg->outlen);
}
static const struct file_operations dfops = {
@ -1268,19 +1262,11 @@ static ssize_t outlen_read(struct file *filp, char __user *buf, size_t count,
char outlen[8];
int err;
if (*pos)
return 0;
err = snprintf(outlen, sizeof(outlen), "%d", dbg->outlen);
if (err < 0)
return err;
if (copy_to_user(buf, &outlen, err))
return -EFAULT;
*pos += err;
return err;
return simple_read_from_buffer(buf, count, pos, outlen, err);
}
static ssize_t outlen_write(struct file *filp, const char __user *buf,

22
drivers/net/ethernet/mellanox/mlx5/core/debugfs.c
View File

@ -150,22 +150,13 @@ static ssize_t average_read(struct file *filp, char __user *buf, size_t count,
int ret;
char tbuf[22];
if (*pos)
return 0;
stats = filp->private_data;
spin_lock_irq(&stats->lock);
if (stats->n)
field = div64_u64(stats->sum, stats->n);
spin_unlock_irq(&stats->lock);
ret = snprintf(tbuf, sizeof(tbuf), "%llu\n", field);
if (ret > 0) {
if (copy_to_user(buf, tbuf, ret))
return -EFAULT;
}
*pos += ret;
return ret;
return simple_read_from_buffer(buf, count, pos, tbuf, ret);
}
static ssize_t average_write(struct file *filp, const char __user *buf,
@ -442,9 +433,6 @@ static ssize_t dbg_read(struct file *filp, char __user *buf, size_t count,
u64 field;
int ret;
if (*pos)
return 0;
desc = filp->private_data;
d = (void *)(desc - desc->i) - sizeof(*d);
switch (d->type) {
@ -470,13 +458,7 @@ static ssize_t dbg_read(struct file *filp, char __user *buf, size_t count,
else
ret = snprintf(tbuf, sizeof(tbuf), "0x%llx\n", field);
if (ret > 0) {
if (copy_to_user(buf, tbuf, ret))
return -EFAULT;
}
*pos += ret;
return ret;
return simple_read_from_buffer(buf, count, pos, tbuf, ret);
}
static const struct file_operations fops = {