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 C3CA13246E8 for ; Sat, 8 Aug 2026 17:14:35 +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=1786209277; cv=none; b=qYsy7yr43i1NDuORoyOUs23ylDMieeakK2N6DdOxVYXJm/i2qhzgzdpENTaIaf2y0GcqkXkI/AwQMUQXSWBvb+Vsc6y2KOUf5DqvvXyge6CZFoMQnQ9p35nAwTzfLiDYiBD582X1gbgTI7C4LYvZL/u+66fe28HgGb5dfjbF2eM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786209277; c=relaxed/simple; bh=i9yN890UOojuHnO0szmO7gkOd5//00uh49X/k/tl7+0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=TP+/6/s4jCmbp+u8pDexw+KskssDaop11t0F4lh5s1EySIQ3O2kYycgHZXzq2KMY1Et1T+7wMPOROKPFgH/1X9EtfDhpaoidcTY9iCfMNU61lklx5myXp6bf+3kb3IwaanFwxeuw0NsRZbaaIhjU8D4zDH4HrmJkcwsteB+4fys= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=EmacfWer; 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="EmacfWer" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D3CD81F00A3E; Sat, 8 Aug 2026 17:14:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786209275; bh=aE55SIi0AnufoB3SLtehpEdLL27ZwNgfJprrLMoSt0c=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=EmacfWero8FPTRHprj4dvYBW33mO9B6pkuC0Tk2MqR/Rlny1zTb316ZZNlEuPGf8E krGLGu1cybcETgdLkBI5BlP+8T8fLKjbS1Fd56HGau4csdZjLdSjjUORp15ZUYdOs+ KP2Hvhn4t8sJxSgyyv/+lmCoIutsXOLLnRC13IieD0JfemdP5pdzKVPkBg4XJdme/P 4js5HzogNGAW1vhVsZCCqtHWF8+Baruourwjh5hFR0SAfsF7GQflhXQZi8Y3sxGkfv BAJ8xv5MbkEEhj6cwUQMbzs7ReErsWT4jJaOwNXkvtuv9catZCgRb12TIbK6yqfxKH jEBOvX+uFUgFw== From: Sasha Levin To: stable@vger.kernel.org Cc: Wentao Guan , Namjae Jeon , Steve French , Sasha Levin Subject: [PATCH 6.1.y 3/3] ksmbd: restore DACL size on check_add_overflow() to avoid malformed ACL Date: Sat, 8 Aug 2026 13:14:24 -0400 Message-ID: <20260808171424.498621-3-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: Wentao Guan [ Upstream commit bbf0a8e931204ecdab494a88d43b0a24a04285c5 ] check_add_overflow() unconditionally writes the truncated sum into *d even on overflow, per its contract in include/linux/overflow.h. The four check_add_overflow() guards in set_posix_acl_entries_dacl() and set_ntacl_dacl() break out of the ACE-building loops on overflow, but the truncated *size is then consumed downstream at the end of set_ntacl_dacl(): pndacl->size = cpu_to_le16(le16_to_cpu(pndacl->size) + size); This produces an on-wire NT ACL whose pndacl->size under-reports the bytes actually written by the preceding fill_ace_for_sid()/memcpy() calls, yielding a malformed ACL that can trigger out-of-bounds reads when re-parsed by clients or ksmbd itself. Restore *size to its pre-addition value on each overflow branch (via `*size -= ace_sz` / `size -= nt_ace_size`) so that after the break, *size once again holds the cumulative size of the successfully-written ACEs. The committed ACL is then truncated-but-self-consistent rather than malformed. The ksmbd DACL builders are the only check_add_overflow() sites found where an overflow path breaks out of a loop and the destination value is consumed afterward. The other nearby break-style cases either return -EINVAL on overflow (transport_ipc.c) or break without consuming the overflowed destination value afterward (buildid.c). Fixes: 299f962c0b02 ("ksmbd: use check_add_overflow() to prevent u16 DACL size overflow") Assisted-by: atomcode:glm-5.2 Assisted-by: Codex:gpt-5.5 Cc: stable@vger.kernel.org Signed-off-by: Wentao Guan Acked-by: Namjae Jeon Signed-off-by: Steve French Signed-off-by: Sasha Levin --- fs/smb/server/smbacl.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/fs/smb/server/smbacl.c b/fs/smb/server/smbacl.c index 45c9b980418e8..2b2d8fbaa392e 100644 --- a/fs/smb/server/smbacl.c +++ b/fs/smb/server/smbacl.c @@ -644,6 +644,7 @@ static void set_posix_acl_entries_dacl(struct user_namespace *user_ns, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, flags, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -658,6 +659,7 @@ static void set_posix_acl_entries_dacl(struct user_namespace *user_ns, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x03, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -703,6 +705,7 @@ static void set_posix_acl_entries_dacl(struct user_namespace *user_ns, ace_sz = fill_ace_for_sid(ntace, sid, ACCESS_ALLOWED, 0x0b, pace->e_perm, 0777); if (check_add_overflow(*size, ace_sz, size)) { + *size -= ace_sz; kfree(sid); break; } @@ -745,8 +748,10 @@ static void set_ntacl_dacl(struct user_namespace *user_ns, goto next_ace; memcpy((char *)pndace + size, ntace, nt_ace_size); - if (check_add_overflow(size, nt_ace_size, &size)) + if (check_add_overflow(size, nt_ace_size, &size)) { + size -= nt_ace_size; break; + } num_aces++; next_ace: -- 2.53.0