Re: [PATCH] habanalabs: fix debugfs code

[Oded Gabbay]

On Sat, May 4, 2019 at 4:56 PM Jann Horn <jannh@xxxxxxxxxx> wrote:
>
> This fixes multiple things in the habanalabs debugfs code, in particular:
>
>  - mmu_write() was unnecessarily verbose, copying around between multiple
>    buffers
>  - mmu_write() could write a user-specified, unbounded amount of userspace
>    memory into a kernel buffer (out-of-bounds write)
>  - multiple debugfs read handlers ignored the user-supplied count,
>    potentially corrupting out-of-bounds userspace data
>  - hl_device_read() was unnecessarily verbose
>  - hl_device_write() could read uninitialized stack memory
>  - multiple debugfs read handlers copied terminating null characters to
>    userspace
>
> Signed-off-by: Jann Horn <jannh@xxxxxxxxxx>
> ---
> compile-tested only, so you might want to test this before applying the
> patch
>
>  drivers/misc/habanalabs/debugfs.c | 60 ++++++++++---------------------
>  1 file changed, 18 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/misc/habanalabs/debugfs.c b/drivers/misc/habanalabs/debugfs.c
> index 974a87789bd86..17ba26422b297 100644
> --- a/drivers/misc/habanalabs/debugfs.c
> +++ b/drivers/misc/habanalabs/debugfs.c
> @@ -459,41 +459,31 @@ static ssize_t mmu_write(struct file *file, const char __user *buf,
>         struct hl_debugfs_entry *entry = s->private;
>         struct hl_dbg_device_entry *dev_entry = entry->dev_entry;
>         struct hl_device *hdev = dev_entry->hdev;
> -       char kbuf[MMU_KBUF_SIZE], asid_kbuf[MMU_ASID_BUF_SIZE],
> -               addr_kbuf[MMU_ADDR_BUF_SIZE];
> +       char kbuf[MMU_KBUF_SIZE];
>         char *c;
>         ssize_t rc;
>
>         if (!hdev->mmu_enable)
>                 return count;
>
> -       memset(kbuf, 0, sizeof(kbuf));
> -       memset(asid_kbuf, 0, sizeof(asid_kbuf));
> -       memset(addr_kbuf, 0, sizeof(addr_kbuf));
> -
> +       if (count > sizeof(kbuf) - 1)
> +               goto err;
>         if (copy_from_user(kbuf, buf, count))
>                 goto err;
> -
> -       kbuf[MMU_KBUF_SIZE - 1] = 0;
> +       kbuf[count] = 0;
>
>         c = strchr(kbuf, ' ');
>         if (!c)
>                 goto err;
> +       *c = '\0';
>
> -       memcpy(asid_kbuf, kbuf, c - kbuf);
> -
> -       rc = kstrtouint(asid_kbuf, 10, &dev_entry->mmu_asid);
> +       rc = kstrtouint(kbuf, 10, &dev_entry->mmu_asid);
>         if (rc)
>                 goto err;
>
> -       c = strstr(kbuf, " 0x");
> -       if (!c)
> +       if (strncmp(c+1, "0x", 2))
>                 goto err;
> -
> -       c += 3;
> -       memcpy(addr_kbuf, c, (kbuf + count) - c);
> -
> -       rc = kstrtoull(addr_kbuf, 16, &dev_entry->mmu_addr);
> +       rc = kstrtoull(c+3, 16, &dev_entry->mmu_addr);
>         if (rc)
>                 goto err;
>
> @@ -525,10 +515,8 @@ static ssize_t hl_data_read32(struct file *f, char __user *buf,
>         }
>
>         sprintf(tmp_buf, "0x%08x\n", val);
> -       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
> -                       strlen(tmp_buf) + 1);
> -
> -       return rc;
> +       return simple_read_from_buffer(buf, count, ppos, tmp_buf,
> +                       strlen(tmp_buf));
>  }
>
>  static ssize_t hl_data_write32(struct file *f, const char __user *buf,
> @@ -559,7 +547,6 @@ static ssize_t hl_get_power_state(struct file *f, char __user *buf,
>         struct hl_dbg_device_entry *entry = file_inode(f)->i_private;
>         struct hl_device *hdev = entry->hdev;
>         char tmp_buf[200];
> -       ssize_t rc;
>         int i;
>
>         if (*ppos)
> @@ -574,10 +561,8 @@ static ssize_t hl_get_power_state(struct file *f, char __user *buf,
>
>         sprintf(tmp_buf,
>                 "current power state: %d\n1 - D0\n2 - D3hot\n3 - Unknown\n", i);
> -       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
> -                       strlen(tmp_buf) + 1);
> -
> -       return rc;
> +       return simple_read_from_buffer(buf, count, ppos, tmp_buf,
> +                       strlen(tmp_buf));
>  }
>
>  static ssize_t hl_set_power_state(struct file *f, const char __user *buf,
> @@ -630,8 +615,8 @@ static ssize_t hl_i2c_data_read(struct file *f, char __user *buf,
>         }
>
>         sprintf(tmp_buf, "0x%02x\n", val);
> -       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
> -                       strlen(tmp_buf) + 1);
> +       rc = simple_read_from_buffer(buf, count, ppos, tmp_buf,
> +                       strlen(tmp_buf));
>
>         return rc;
>  }
> @@ -720,18 +705,9 @@ static ssize_t hl_led2_write(struct file *f, const char __user *buf,
>  static ssize_t hl_device_read(struct file *f, char __user *buf,
>                                         size_t count, loff_t *ppos)
>  {
> -       char tmp_buf[200];
> -       ssize_t rc;
> -
> -       if (*ppos)
> -               return 0;
> -
> -       sprintf(tmp_buf,
> -               "Valid values: disable, enable, suspend, resume, cpu_timeout\n");
> -       rc = simple_read_from_buffer(buf, strlen(tmp_buf) + 1, ppos, tmp_buf,
> -                       strlen(tmp_buf) + 1);
> -
> -       return rc;
> +       static const char *help =
> +               "Valid values: disable, enable, suspend, resume, cpu_timeout\n";
> +       return simple_read_from_buffer(buf, count, ppos, help, strlen(help));
>  }
>
>  static ssize_t hl_device_write(struct file *f, const char __user *buf,
> @@ -739,7 +715,7 @@ static ssize_t hl_device_write(struct file *f, const char __user *buf,
>  {
>         struct hl_dbg_device_entry *entry = file_inode(f)->i_private;
>         struct hl_device *hdev = entry->hdev;
> -       char data[30];
> +       char data[30] = {0};
>
>         /* don't allow partial writes */
>         if (*ppos != 0)
> --
> 2.21.0.1020.gf2820cf01a-goog
>

Thanks!
Will be applied to my -next branch

This patch is:
Reviewed-by: Oded Gabbay <oded.gabbay@xxxxxxxxx>