On Thu, Nov 10, 2022 at 11:10:24AM +0800, Zhen Lei wrote:
> UBSAN: shift-out-of-bounds in fs/locks.c:2572:16
> left shift of 1 by 63 places cannot be represented in type 'long long int'
>
> Switch the calculation method to ((quarter - 1) * 2 + 1) can help us
> eliminate this false positive.
>
> On the other hand, the old implementation has problems with char and
> short types, although not currently involved.
> printf("%d: %x\n", sizeof(char), INT_LIMIT(char));
> printf("%d: %x\n", sizeof(short), INT_LIMIT(short));
> 1: ffffff7f
> 2: ffff7fff
>
> Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
> ---
> include/linux/fs.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index e654435f16512c1..88d42e2daed9f6c 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1131,7 +1131,7 @@ struct file_lock_context {
>
> /* The following constant reflects the upper bound of the file/locking space */
> #ifndef OFFSET_MAX
> -#define INT_LIMIT(x) (~((x)1 << (sizeof(x)*8 - 1)))
> +#define INT_LIMIT(x) ((((x)1 << (sizeof(x) * 8 - 2)) - 1) * 2 + 1)
> #define OFFSET_MAX INT_LIMIT(loff_t)
> #define OFFT_OFFSET_MAX INT_LIMIT(off_t)
> #endif
This problem has already been solved by type_max() in include/linux/overflow.h.
How about removing INT_LIMIT() and using type_max() instead?
- Eric
