[v2,0/2] fs: clear a UBSAN shift-out-of-bounds warning

Message

Zhen Lei Nov. 21, 2022, 2:44 a.m. UTC

v1 -- > v2:
1. Replace INT_LIMIT(loff_t) with OFFSET_MAX in btrfs.
2. Replace INT_LIMIT() with type_max().

Zhen Lei (2):
  btrfs: replace INT_LIMIT(loff_t) with OFFSET_MAX
  fs: clear a UBSAN shift-out-of-bounds warning

 fs/btrfs/ordered-data.c | 6 +++---
 include/linux/fs.h      | 5 ++---
 2 files changed, 5 insertions(+), 6 deletions(-)

Comments

Al Viro Nov. 25, 2022, 6:43 a.m. UTC | #1

On Mon, Nov 21, 2022 at 10:44:16AM +0800, Zhen Lei wrote:
> v1 -- > v2:
> 1. Replace INT_LIMIT(loff_t) with OFFSET_MAX in btrfs.
> 2. Replace INT_LIMIT() with type_max().

Looks fine, except that I'd rather go for commit message
along the lines of "INT_LIMIT tries to do what type_max does,
except that type_max doesn't rely upon undefined behaviour;
might as well use type_max() instead"

If you want to credit UBSAN - sure, no problem, just don't
clutter the commit message with that.  As it is, it reads
as "make $TOOL STFU"...

Zhen Lei Nov. 25, 2022, 8:33 a.m. UTC | #2

On 2022/11/25 14:43, Al Viro wrote:
> On Mon, Nov 21, 2022 at 10:44:16AM +0800, Zhen Lei wrote:
>> v1 -- > v2:
>> 1. Replace INT_LIMIT(loff_t) with OFFSET_MAX in btrfs.
>> 2. Replace INT_LIMIT() with type_max().
> 
> Looks fine, except that I'd rather go for commit message
> along the lines of "INT_LIMIT tries to do what type_max does,
> except that type_max doesn't rely upon undefined behaviour;
> might as well use type_max() instead"

Very good. Do I send v3, or do you update it?

> 
> If you want to credit UBSAN - sure, no problem, just don't
> clutter the commit message with that.  As it is, it reads
> as "make $TOOL STFU"...

Okay, I'll pay attention next time. This USBAN problem is relatively
simple and can be located without relying on other information, so I
omitted the rest.

After changing to your suggested description, it seems that there is
no need to mention UBSAN, after all, it is just a false positive and
there is no real problem.

> 
> .
>