On Fri, Aug 9, 2019 at 4:28 AM Jia He <justin...@arm.com> wrote:
>
> Commit 3e5903eb9cff ("vsprintf: Prevent crash when dereferencing invalid
> pointers") prevents most crash except for %pD.
> There is an additional pointer dereferencing before dentry_name.
>
> At least, vma->file can be NULL and be passed to printk %pD in
> print_bad_pte, which can cause crash.
>
> This patch fixes it with introducing a new file_dentry_name.
>
Reviewed-by: Andy Shevchenko <andy.shevche...@gmail.com>
Perhaps you need to add a Fixes tag
> Signed-off-by: Jia He <justin...@arm.com>
> ---
> lib/vsprintf.c | 13 ++++++++++---
> 1 file changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 63937044c57d..b4a119176fdb 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -869,6 +869,15 @@ char *dentry_name(char *buf, char *end, const struct
> dentry *d, struct printf_sp
> return widen_string(buf, n, end, spec);
> }
>
> +static noinline_for_stack
> +char *file_dentry_name(char *buf, char *end, const struct file *f,
> + struct printf_spec spec, const char *fmt)
> +{
> + if (check_pointer(&buf, end, f, spec))
> + return buf;
> +
> + return dentry_name(buf, end, f->f_path.dentry, spec, fmt);
> +}
> #ifdef CONFIG_BLOCK
> static noinline_for_stack
> char *bdev_name(char *buf, char *end, struct block_device *bdev,
> @@ -2166,9 +2175,7 @@ char *pointer(const char *fmt, char *buf, char *end,
> void *ptr,
> case 'C':
> return clock(buf, end, ptr, spec, fmt);
> case 'D':
> - return dentry_name(buf, end,
> - ((const struct file *)ptr)->f_path.dentry,
> - spec, fmt);
> + return file_dentry_name(buf, end, ptr, spec, fmt);
> #ifdef CONFIG_BLOCK
> case 'g':
> return bdev_name(buf, end, ptr, spec, fmt);
> --
> 2.17.1
>
--
With Best Regards,
Andy Shevchenko
