[for-4.19] livepatch: use appropriate type for buffer offset variables

Commit Message

Jan Beulich June 20, 2024, 7:15 a.m. UTC

As was made noticeable by the last of the commits referenced below,
using a fixed-size type for such purposes is not only against
./CODING_STYLE, but can lead to actual issues. Switch to using size_t
instead, thus also allowing calculations to be lighter-weight in 32-bit
builds.

No functional change for 64-bit builds.

Link: https://gitlab.com/xen-project/xen/-/jobs/7136417308
Fixes: b145b4a39c13 ("livepatch: Handle arbitrary size names with the list operation")
Fixes: 5083e0ff939d ("livepatch: Add metadata runtime retrieval mechanism")
Fixes: 43d5c5d5f70b ("xen: avoid UB in guest handle arithmetic")
Reported-by: Andrew Cooper <[e-mail]>
Signed-off-by: Jan Beulich <[e-mail]>

Comments

Ross Lagerwall June 20, 2024, 8:04 a.m. UTC | #1

On Thu, Jun 20, 2024 at 8:16 AM Jan Beulich <[e-mail]> wrote:
>
> As was made noticeable by the last of the commits referenced below,
> using a fixed-size type for such purposes is not only against
> ./CODING_STYLE, but can lead to actual issues. Switch to using size_t
> instead, thus also allowing calculations to be lighter-weight in 32-bit
> builds.
>
> No functional change for 64-bit builds.
>
> Link: https://gitlab.com/xen-project/xen/-/jobs/7136417308
> Fixes: b145b4a39c13 ("livepatch: Handle arbitrary size names with the list operation")
> Fixes: 5083e0ff939d ("livepatch: Add metadata runtime retrieval mechanism")
> Fixes: 43d5c5d5f70b ("xen: avoid UB in guest handle arithmetic")
> Reported-by: Andrew Cooper <[e-mail]>
> Signed-off-by: Jan Beulich <[e-mail]>
>

Reviewed-by: Ross Lagerwall <[e-mail]>

Thanks

Oleksii Kurochko June 20, 2024, 9:46 a.m. UTC | #2

On Thu, 2024-06-20 at 09:04 +0100, Ross Lagerwall wrote:
> On Thu, Jun 20, 2024 at 8:16 AM Jan Beulich <[e-mail]>
> wrote:
> > 
> > As was made noticeable by the last of the commits referenced below,
> > using a fixed-size type for such purposes is not only against
> > ./CODING_STYLE, but can lead to actual issues. Switch to using
> > size_t
> > instead, thus also allowing calculations to be lighter-weight in
> > 32-bit
> > builds.
> > 
> > No functional change for 64-bit builds.
> > 
> > Link: https://gitlab.com/xen-project/xen/-/jobs/7136417308
> > Fixes: b145b4a39c13 ("livepatch: Handle arbitrary size names with
> > the list operation")
> > Fixes: 5083e0ff939d ("livepatch: Add metadata runtime retrieval
> > mechanism")
> > Fixes: 43d5c5d5f70b ("xen: avoid UB in guest handle arithmetic")
> > Reported-by: Andrew Cooper <[e-mail]>
> > Signed-off-by: Jan Beulich <[e-mail]>
> > 
> 
> Reviewed-by: Ross Lagerwall <[e-mail]>
Release-Acked-by: Oleksii Kurochko <[e-mail]>

~ Oleksii

Patch

--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -1252,7 +1252,7 @@  static int livepatch_list(struct xen_sys
     list->metadata_total_size = 0;
     if ( list->nr )
     {
-        uint64_t name_offset = 0, metadata_offset = 0;
+        size_t name_offset = 0, metadata_offset = 0;
 
         list_for_each_entry( data, &payload_list, list )
         {