From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 C76D633B6F1 for ; Sat, 8 Aug 2026 17:14:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786209275; cv=none; b=ccbOHGVpU7zgNFWPYn7HUgQCo8uQBkQRbXHUhVw9WuGdUe8VEumj/dJjpzRMsayY/gw+OdPCXXqxybZRPiWL4FfVtdanRTTQE53Zrc/nNCXpJ0rYqwCAkJ3b7LZjQtVobn5b8hxXh9fvOYpGzI+gcvAY10dJ8SdmFKElfKtIj+4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786209275; c=relaxed/simple; bh=NVxEMPHGFoY4x/rwxyavYgnAb9phpv55LWC2IzTuEFg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fPSA+30qHGKis1prgM1DkpeGmUCT5byHfqzv4e4pwHoq4XHqp9NCyiyYcA0msKe5A+8CYGWYCt9BAAXS34wS6fGy73h4FS5hsRsoi0VeGEx+KBguuTfNDQz8d1yvSHr++jfB9nZNR5JoNaTvxEtpVNs74sTaXWOjdFaPjTzJT84= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=WNB7Jb7I; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="WNB7Jb7I" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E67AC1F00A3A; Sat, 8 Aug 2026 17:14:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786209274; bh=8xWelVZQPE53mNeeJ6dqqoT3p34Zw7aHxDI9oqftdUw=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=WNB7Jb7IPQowF+t/NHY01hVNSAHyU0ewmFEY1DmSVOd+k0DUuT3eY8ugjQng+XydX /BC7sKje4xPkVCCAprbfeaj7lz3A7sOl/ORX3CsbDqy9DXqGoSHrmrlijM5X05IMJn UpWuivumjqufPRYm7xCTzibA19NWtS9Ja4zwE3BK6YifWE390BkluPGrbYYg2KVfdR ELsBnLqKNKD6rZRzdA4IhK6cLwelJmMKsZMTmguJDqA2BIXOC8u5QKIGLPkabbtbI6 RkinuTTe9ZmMP2UfM9oKO4nYRYWApMlWk1MLZa/gUPT/zt6xwXPILGUSZd59pffR8N VtvLXNzKxlP0w== From: Sasha Levin To: stable@vger.kernel.org Cc: Haofeng Li , ChenXiaoSong , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 6.1.y 2/3] ksmbd: validate num_subauth when copying ACE in set_ntacl_dacl Date: Sat, 8 Aug 2026 13:14:23 -0400 Message-ID: <20260808171424.498621-2-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260808171424.498621-1-sashal@kernel.org> References: <2026072937-broadcast-renewal-0307@gregkh> <20260808171424.498621-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Haofeng Li [ Upstream commit 47f0b34f6bc98ed85bfdc293e8f3e432ec24958d ] set_ntacl_dacl() copies each ACE from the attacker-controlled stored security descriptor verbatim into the response DACL without checking sid.num_subauth. The ACE bytes (including an unchecked num_subauth) originate from an authenticated SMB2_SET_INFO(SecInfo=DACL) that is stored raw via ksmbd_vfs_set_sd_xattr(); parse_dacl() rejects a bad ACE with `break` rather than an error, so parse_sec_desc() still returns success and the malformed SD reaches the xattr intact. On a subsequent SMB2_QUERY_INFO(SecInfo=DACL) for an inode carrying a POSIX access ACL, build_sec_desc() -> set_ntacl_dacl() -> set_posix_acl_entries_dacl() walks the copied ACEs and reads ntace->sid.sub_auth[ntace->sid.num_subauth - 1] with num_subauth taken straight from the stored SD. Since sub_auth[] is fixed at SID_MAX_SUB_AUTHORITIES (15), a crafted num_subauth (e.g. 255) drives an out-of-bounds heap read of ~1 KB with an offset fully controlled by an authenticated client. The sibling functions already gate this field: parse_dacl() -- num_subauth == 0 || > SID_MAX_SUB_AUTHORITIES parse_sid() -- num_subauth > SID_MAX_SUB_AUTHORITIES smb_copy_sid() -- min_t(u8, num_subauth, SID_MAX_SUB_AUTHORITIES) set_ntacl_dacl() is the lone inconsistent path that omits the check. Add the same num_subauth validation in set_ntacl_dacl() before copying the ACE, matching the gate already enforced by parse_dacl(). Signed-off-by: Haofeng Li Reviewed-by: ChenXiaoSong Suggested-by: Namjae Jeon Acked-by: Namjae Jeon Signed-off-by: Steve French Stable-dep-of: bbf0a8e93120 ("ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL") Signed-off-by: Sasha Levin --- fs/smb/server/smbacl.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c index 3a250ddb1a2a9..45c9b980418e8 100644 --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -740,12 +740,18 @@ static void set_ntacl_dacl(struct user_namespace *user_ns, if (nt_ace_size > aces_size) break; + if (ntace->sid.num_subauth == 0 || + ntace->sid.num_subauth > SID_MAX_SUB_AUTHORITIES) + goto next_ace; + memcpy((char *)pndace + size, ntace, nt_ace_size); if (check_add_overflow(size, nt_ace_size, &size)) break; + num_aces++; + +next_ace: aces_size -= nt_ace_size; ntace = (struct smb_ace *)((char *)ntace + nt_ace_size); - num_aces++; } } -- 2.53.0