linux-hardening - [PATCH] Revert "bcachefs: Annotate struct bch_xattr with __counted

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Message-ID: <20250501184150.200319-1-mmpgouride@gmail.com>
Date: Fri,  2 May 2025 02:41:50 +0800
From: Alan Huang <mmpgouride@...il.com>
To: kent.overstreet@...ux.dev,
	kees@...nel.org,
	gustavoars@...nel.org,
	thorsten.blum@...lux.com
Cc: linux-bcachefs@...r.kernel.org,
	linux-hardening@...r.kernel.org,
	Alan Huang <mmpgouride@...il.com>
Subject: [PATCH] Revert "bcachefs: Annotate struct bch_xattr with __counted_by()"

This reverts commit 86e92eeeb23741a072fe7532db663250ff2e726a.

After the x_name, there is a value. According to the disscussion[1],
__counted_by assumes that the flexible array member contains exactly
the amount of elements that are specified. Now there are users came across
buffer overflow caused by the __counted_by here[2], so revert that.

[1] https://lore.kernel.org/lkml/Zv8VDKWN1GzLRT-_@archlinux/T/#m0ce9541c5070146320efd4f928cc1ff8de69e9b2
[2] https://privatebin.net/?a0d4e97d590d71e1#9bLmp2Kb5NU6X6cZEucchDcu88HzUQwHUah8okKPReEt

Signed-off-by: Alan Huang <mmpgouride@...il.com>
---
 fs/bcachefs/xattr_format.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/bcachefs/xattr_format.h b/fs/bcachefs/xattr_format.h
index c7916011ef34..e9f810539552 100644
--- a/fs/bcachefs/xattr_format.h
+++ b/fs/bcachefs/xattr_format.h
@@ -13,7 +13,7 @@ struct bch_xattr {
 	__u8			x_type;
 	__u8			x_name_len;
 	__le16			x_val_len;
-	__u8			x_name[] __counted_by(x_name_len);
+	__u8			x_name[];
 } __packed __aligned(8);
 
 #endif /* _BCACHEFS_XATTR_FORMAT_H */
-- 
2.48.1