mbox series

[v3,0/2] fs: clear a UBSAN shift-out-of-bounds warning

Message ID 20221125091358.1963-1-thunder.leizhen@huawei.com (mailing list archive)
Headers show
Series fs: clear a UBSAN shift-out-of-bounds warning | expand

Message

Zhen Lei Nov. 25, 2022, 9:13 a.m. UTC 
v2 --> v3:
Updated the commit message of patch 2/2 based on Alexander Viro's suggestion.

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, 9 p.m. UTC | #1 
On Fri, Nov 25, 2022 at 05:13:56PM +0800, Zhen Lei wrote:
> v2 --> v3:
> Updated the commit message of patch 2/2 based on Alexander Viro's suggestion.

Not exactly what I meant...  I've tentatively applied it, with the
following commit message:

--------------------------------
get rid of INT_LIMIT, use type_max() instead

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 T is an N-bit signed integer type, the maximal value in T is
pow(2, N - 1) - 1, all right, but naive expression for that value
ends up with a couple of wraparounds and as usual for wraparounds
in signed types, that's an undefined behaviour.  type_max() takes
care to avoid those...

Caught-by: UBSAN
Suggested-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
--------------------------------

Does anybody have objections against the commit message above?
Zhen Lei Nov. 26, 2022, 1:59 a.m. UTC | #2 
On 2022/11/26 5:00, Al Viro wrote:
> On Fri, Nov 25, 2022 at 05:13:56PM +0800, Zhen Lei wrote:
>> v2 --> v3:
>> Updated the commit message of patch 2/2 based on Alexander Viro's suggestion.
> 
> Not exactly what I meant...  I've tentatively applied it, with the

Haha, I felt like something was missing yesterday, too. But as far as my English
level is concerned, I usually copy the words suggested by others directly.

> following commit message:

Thanks.

> 
> --------------------------------
> get rid of INT_LIMIT, use type_max() instead
> 
> 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 T is an N-bit signed integer type, the maximal value in T is
> pow(2, N - 1) - 1, all right, but naive expression for that value
> ends up with a couple of wraparounds and as usual for wraparounds
> in signed types, that's an undefined behaviour.  type_max() takes
> care to avoid those...
> 
> Caught-by: UBSAN
> Suggested-by: Eric Biggers <ebiggers@kernel.org>
> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
> Reviewed-by: Eric Biggers <ebiggers@google.com>
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> --------------------------------
> 
> Does anybody have objections against the commit message above?

Looks good to me.

> 
> .
>