On Mon, Jul 20, 2020 at 09:18:55 +0200, Alexander Strasser wrote: > On 2020-07-19 19:47 -0400, Andriy Gelman wrote: > > > > This check seems dead code. Looking at xcb sources, cursor is just an > > > > offset in > > > > memory from ci so I don't think it can be null here.
> > But anyway, this part of the patch doesn't really have anything to do with > > ticket #7312, and should be in a separate patch. > > Yes, it's definitely something that was changed in this patch > at all. So it's better not to touch it in this patch. Okay, so I "fixed" dead code. You guys can remove the dead code yourselves then, if you like. ;-) New patch for the original issue attached, not touching the dead code. Thanks, Moritz
From e44b7f03354add2272a2739e04aafb38b7ce027f Mon Sep 17 00:00:00 2001 From: Moritz Barsnick <[email protected]> Date: Wed, 5 Aug 2020 14:06:53 +0200 Subject: [PATCH] avdevice/xcbgrab: check return values of xcb query functions Fixes #7312, segmentation fault on close of X11 server xcb_query_pointer_reply() and xcb_get_geometry_reply() can return NULL if e.g. the X server closes or the connection is lost. This needs to be checked in order to cleanly exit, because the returned pointers are dereferenced later. Signed-off-by: Moritz Barsnick <[email protected]> --- libavdevice/xcbgrab.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/libavdevice/xcbgrab.c b/libavdevice/xcbgrab.c index 6f6b2dbf15..8ef2a30d02 100644 --- a/libavdevice/xcbgrab.c +++ b/libavdevice/xcbgrab.c @@ -425,7 +425,16 @@ static int xcbgrab_read_packet(AVFormatContext *s, AVPacket *pkt) pc = xcb_query_pointer(c->conn, c->screen->root); gc = xcb_get_geometry(c->conn, c->screen->root); p = xcb_query_pointer_reply(c->conn, pc, NULL); + if (!p) { + av_log(s, AV_LOG_ERROR, "Failed to query xcb pointer\n"); + return AVERROR_EXTERNAL; + } geo = xcb_get_geometry_reply(c->conn, gc, NULL); + if (!geo) { + av_log(s, AV_LOG_ERROR, "Failed to get xcb geometry\n"); + free(p); + return AVERROR_EXTERNAL; + } } if (c->follow_mouse && p->same_screen) -- 2.26.2
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