From cb4fd4d06ee8bd71b7176f58ecad70b69e3702d8 Mon Sep 17 00:00:00 2001 From: Peter Hutterer Date: Tue, 5 Jul 2022 12:06:20 +1000 Subject: [PATCH] xkb: proof GetCountedString against request length attacks GetCountedString did a check for the whole string to be within the request buffer but not for the initial 2 bytes that contain the length field. A swapped client could send a malformed request to trigger a swaps() on those bytes, writing into random memory. Signed-off-by: Peter Hutterer (cherry picked from commit 11beef0b7f1ed290348e45618e5fa0d2bffcb72e) --- xkb/xkb.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/xkb/xkb.c b/xkb/xkb.c index 3084a535b..0f5739b58 100644 --- a/xkb/xkb.c +++ b/xkb/xkb.c @@ -5138,6 +5138,11 @@ _GetCountedString(char **wire_inout, ClientPtr client, char **str) CARD16 len; wire = *wire_inout; + + if (client->req_len < + bytes_to_int32(wire + 2 - (char *) client->requestBuffer)) + return BadValue; + len = *(CARD16 *) wire; if (client->swapped) { swaps(&len);