From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E841F32C92D; Fri, 17 Oct 2025 15:12:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760713931; cv=none; b=kfxE18k2qx49kq9DU6YaH0p8cBcv+wZ+M4FR7UocS1ee7TsLET6BTRrN4tX9IU7yPxboW41wC0cJTzMFTiiBdIKeoENpkh995QJTb5xfuSecYZ4Yl3ExI0hyF4tUAMOSa8o0v8UL7YDHD/pOWv9W9uRMWL0/dz8vdDXi/yiUNuA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760713931; c=relaxed/simple; bh=w/P1onfkEOE2Dwq+Cgvs+KJEN+E2hjElHmxKhXPPNRY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=MTqhnzu8R0qY8/LOABZtcxqskRpoeqK/r+V0+/fIzIRlJKKoz710BKmGM0zCkqPt2e4r9LSGkPJmZgmxayQGv1wiXJPMhEcCMg4CQiu7V/EHSynnZ0B7I5BY1brbcq5IZsB6X2/M0bJFSzDM8h6jWTZGRuVwAyBPeFmebLgY67s= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=BX5bTtM7; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="BX5bTtM7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BD80C4CEFE; Fri, 17 Oct 2025 15:12:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1760713930; bh=w/P1onfkEOE2Dwq+Cgvs+KJEN+E2hjElHmxKhXPPNRY=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BX5bTtM7Yba/cqiMggNhwGOxlaC0os2He7MS3UJI+WIP8qazkG5b4+M0gVmQfM5qY DRATSy+/04mk45nPsYTHpGA0wO1rTo9+HuCtCxlE6LUeuwKIoVwr5WvOio+ieum1ss JyY5MSeaLXr1e7heF7f9NLdPHvCZ9vtQD4v3idws= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+0be4f339a8218d2a5bb1@syzkaller.appspotmail.com, stable@kernel.org, Albin Babu Varghese , Ahmet Eray Karadag , Theodore Tso Subject: [PATCH 6.6 152/201] ext4: guard against EA inode refcount underflow in xattr update Date: Fri, 17 Oct 2025 16:53:33 +0200 Message-ID: <20251017145140.316176074@linuxfoundation.org> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251017145134.710337454@linuxfoundation.org> References: <20251017145134.710337454@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Ahmet Eray Karadag commit 57295e835408d8d425bef58da5253465db3d6888 upstream. syzkaller found a path where ext4_xattr_inode_update_ref() reads an EA inode refcount that is already <= 0 and then applies ref_change (often -1). That lets the refcount underflow and we proceed with a bogus value, triggering errors like: EXT4-fs error: EA inode ref underflow: ref_count=-1 ref_change=-1 EXT4-fs warning: ea_inode dec ref err=-117 Make the invariant explicit: if the current refcount is non-positive, treat this as on-disk corruption, emit ext4_error_inode(), and fail the operation with -EFSCORRUPTED instead of updating the refcount. Delete the WARN_ONCE() as negative refcounts are now impossible; keep error reporting in ext4_error_inode(). This prevents the underflow and the follow-on orphan/cleanup churn. Reported-by: syzbot+0be4f339a8218d2a5bb1@syzkaller.appspotmail.com Fixes: https://syzbot.org/bug?extid=0be4f339a8218d2a5bb1 Cc: stable@kernel.org Co-developed-by: Albin Babu Varghese Signed-off-by: Albin Babu Varghese Signed-off-by: Ahmet Eray Karadag Message-ID: <20250920021342.45575-1-eraykrdg1@gmail.com> Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/xattr.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -1036,7 +1036,7 @@ static int ext4_xattr_inode_update_ref(h int ref_change) { struct ext4_iloc iloc; - s64 ref_count; + u64 ref_count; int ret; inode_lock_nested(ea_inode, I_MUTEX_XATTR); @@ -1046,13 +1046,17 @@ static int ext4_xattr_inode_update_ref(h goto out; ref_count = ext4_xattr_inode_get_ref(ea_inode); + if ((ref_count == 0 && ref_change < 0) || (ref_count == U64_MAX && ref_change > 0)) { + ext4_error_inode(ea_inode, __func__, __LINE__, 0, + "EA inode %lu ref wraparound: ref_count=%lld ref_change=%d", + ea_inode->i_ino, ref_count, ref_change); + ret = -EFSCORRUPTED; + goto out; + } ref_count += ref_change; ext4_xattr_inode_set_ref(ea_inode, ref_count); if (ref_change > 0) { - WARN_ONCE(ref_count <= 0, "EA inode %lu ref_count=%lld", - ea_inode->i_ino, ref_count); - if (ref_count == 1) { WARN_ONCE(ea_inode->i_nlink, "EA inode %lu i_nlink=%u", ea_inode->i_ino, ea_inode->i_nlink); @@ -1061,9 +1065,6 @@ static int ext4_xattr_inode_update_ref(h ext4_orphan_del(handle, ea_inode); } } else { - WARN_ONCE(ref_count < 0, "EA inode %lu ref_count=%lld", - ea_inode->i_ino, ref_count); - if (ref_count == 0) { WARN_ONCE(ea_inode->i_nlink != 1, "EA inode %lu i_nlink=%u",