On Fri, 2018-09-07 at 12:16 -0700, Eric Biggers wrote:
> From: Eric Biggers <ebiggers@xxxxxxxxxx>
>
> On 32-bit systems, the buffer allocated by kernel_read_file() is too
> small if the file size is > SIZE_MAX, due to truncation to size_t.
>
> Fortunately, since the 'count' argument to kernel_read() is also
> truncated to size_t, only the allocated space is filled; then, -EIO is
> returned since 'pos != i_size' after the read loop.
>
> But this is not obvious and seems incidental. We should be more
> explicit about this case. So, fail early if i_size > SIZE_MAX.
>
> Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
Thanks!
> ---
> fs/exec.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/exec.c b/fs/exec.c
> index 1ebf6e5a521d..fc281b738a98 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -908,14 +908,14 @@ int kernel_read_file(struct file *file, void **buf, loff_t *size,
> goto out;
>
> i_size = i_size_read(file_inode(file));
> - if (max_size > 0 && i_size > max_size) {
> - ret = -EFBIG;
> - goto out;
> - }
> if (i_size <= 0) {
> ret = -EINVAL;
> goto out;
> }
> + if (i_size > SIZE_MAX || (max_size > 0 && i_size > max_size)) {
> + ret = -EFBIG;
> + goto out;
> + }
>
> if (id != READING_FIRMWARE_PREALLOC_BUFFER)
> *buf = vmalloc(i_size);
