linux-kernel - [PATCH][next] udf: Fix undefined behavior bug in struct udf_fileident

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Message-ID: <ZRrsYkKIQe8K6F/t@work>
Date:   Mon, 2 Oct 2023 18:14:26 +0200
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Jan Kara <jack@...e.com>
Cc:     linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        linux-hardening@...r.kernel.org
Subject: [PATCH][next] udf: Fix undefined behavior bug in struct
 udf_fileident_iter

`struct fileIdentDesc` is a flexible structure, which means that it
contains a flexible-array member at the bottom. This could potentially
lead to an overwrite of the objects following `fi` in `struct
udf_fileident_iter` at run-time.

Fix this by placing the declaration of object `fi` at the end of
`struct udf_fileident_iter`.

-Wflex-array-member-not-at-end is coming in GCC-14, and we are getting
ready to enable it globally.

Fixes: d16076d9b684 ("udf: New directory iteration code")
Cc: stable@...r.kernel.org
Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 fs/udf/udfdecl.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index 88692512a466..736f591abc89 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -93,11 +93,11 @@ struct udf_fileident_iter {
 	sector_t loffset;		/* Block offset of 'pos' within above
 					 * extent */
 	struct extent_position epos;	/* Position after the above extent */
-	struct fileIdentDesc fi;	/* Copied directory entry */
 	uint8_t *name;			/* Pointer to entry name */
 	uint8_t *namebuf;		/* Storage for entry name in case
 					 * the name is split between two blocks
 					 */
+	struct fileIdentDesc fi;	/* Copied directory entry */
 };
 
 struct udf_vds_record {
-- 
2.34.1