[PATCH] dm integrity: Use struct_group() to zero struct journal_sector

[PATCH] dm integrity: Use struct_group() to zero struct journal_sector

[Kees Cook]

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Add struct_group() to mark region of struct journal_sector that should be
initialized to zero.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 drivers/md/dm-integrity.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
index 6319deccbe09..163c94ca4e5c 100644
--- a/drivers/md/dm-integrity.c
+++ b/drivers/md/dm-integrity.c
@@ -121,8 +121,10 @@ struct journal_entry {
 #define JOURNAL_MAC_SIZE		(JOURNAL_MAC_PER_SECTOR * JOURNAL_BLOCK_SECTORS)
 
 struct journal_sector {
-	__u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
-	__u8 mac[JOURNAL_MAC_PER_SECTOR];
+	struct_group(sectors,
+		__u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
+		__u8 mac[JOURNAL_MAC_PER_SECTOR];
+	);
 	commit_id_t commit_id;
 };
 
@@ -2870,7 +2872,8 @@ static void init_journal(struct dm_integrity_c *ic, unsigned start_section,
 		wraparound_section(ic, &i);
 		for (j = 0; j < ic->journal_section_sectors; j++) {
 			struct journal_sector *js = access_journal(ic, i, j);
-			memset(&js->entries, 0, JOURNAL_SECTOR_DATA);
+			BUILD_BUG_ON(sizeof(js->sectors) != JOURNAL_SECTOR_DATA);
+			memset(&js->sectors, 0, sizeof(js->sectors));
 			js->commit_id = dm_integrity_commit_id(ic, i, j, commit_seq);
 		}
 		for (j = 0; j < ic->journal_section_entries; j++) {
-- 
2.30.2

Re: [dm-devel] [PATCH] dm integrity: Use struct_group() to zero struct journal_sector

[Gustavo A. R. Silva]

On Thu, Nov 18, 2021 at 12:36:40PM -0800, Kees Cook wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
> 
> Add struct_group() to mark region of struct journal_sector that should be
> initialized to zero.
> 
> Signed-off-by: Kees Cook <keescook@chromium.org>

Reviewed-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks
--
Gustavo

> ---
>  drivers/md/dm-integrity.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/md/dm-integrity.c b/drivers/md/dm-integrity.c
> index 6319deccbe09..163c94ca4e5c 100644
> --- a/drivers/md/dm-integrity.c
> +++ b/drivers/md/dm-integrity.c
> @@ -121,8 +121,10 @@ struct journal_entry {
>  #define JOURNAL_MAC_SIZE		(JOURNAL_MAC_PER_SECTOR * JOURNAL_BLOCK_SECTORS)
>  
>  struct journal_sector {
> -	__u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
> -	__u8 mac[JOURNAL_MAC_PER_SECTOR];
> +	struct_group(sectors,
> +		__u8 entries[JOURNAL_SECTOR_DATA - JOURNAL_MAC_PER_SECTOR];
> +		__u8 mac[JOURNAL_MAC_PER_SECTOR];
> +	);
>  	commit_id_t commit_id;
>  };
>  
> @@ -2870,7 +2872,8 @@ static void init_journal(struct dm_integrity_c *ic, unsigned start_section,
>  		wraparound_section(ic, &i);
>  		for (j = 0; j < ic->journal_section_sectors; j++) {
>  			struct journal_sector *js = access_journal(ic, i, j);
> -			memset(&js->entries, 0, JOURNAL_SECTOR_DATA);
> +			BUILD_BUG_ON(sizeof(js->sectors) != JOURNAL_SECTOR_DATA);
> +			memset(&js->sectors, 0, sizeof(js->sectors));
>  			js->commit_id = dm_integrity_commit_id(ic, i, j, commit_seq);
>  		}
>  		for (j = 0; j < ic->journal_section_entries; j++) {
> -- 
> 2.30.2
> 
> --
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