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Date:   Tue, 3 Oct 2023 11:26:43 +0200
From:   Jan Kara <jack@suse.cz>
To:     "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc:     Jan Kara <jack@suse.com>, linux-kernel@vger.kernel.org,
        linux-hardening@vger.kernel.org
Subject: Re: [PATCH][next] udf: Fix undefined behavior bug in struct
 udf_fileident_iter
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On Mon 02-10-23 18:14:26, Gustavo A. R. Silva wrote:
> `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@vger.kernel.org
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks for the patch! This is in fact harmless since we never use the
impUse field. But I agree it is confusing so I'll merge attached fix
instead.

								Honza
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

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	filename="0001-udf-Avoid-unneeded-variable-length-array-in-struct-f.patch"

From 7b530e7ad261dc6111874f2225c2f38f63d12ebf Mon Sep 17 00:00:00 2001
From: Jan Kara <jack@suse.cz>
Date: Tue, 3 Oct 2023 11:19:02 +0200
Subject: [PATCH] udf: Avoid unneeded variable length array in struct
 fileIdentDesc

impUse variable length array in struct fileIdentDesc is never used.
It serves only for documentation purposes of the on-disk format. Remove
it from the struct so that it doesn't confuse the compiler and
reviewers.

Reported-by: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/udf/ecma_167.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/udf/ecma_167.h b/fs/udf/ecma_167.h
index de17a97e8667..415b050b977d 100644
--- a/fs/udf/ecma_167.h
+++ b/fs/udf/ecma_167.h
@@ -471,7 +471,7 @@ struct fileIdentDesc {
 	uint8_t		lengthFileIdent;
 	struct long_ad	icb;
 	__le16		lengthOfImpUse;
-	uint8_t		impUse[];
+	/* uint8_t	impUse[]; */
 	/* uint8_t	fileIdent[]; */
 	/* uint8_t	padding[]; */
 } __packed;
-- 
2.35.3


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