From 48e8da851d3ddfd7147353f1d06993c95c5f27d2 Mon Sep 17 00:00:00 2001 From: Dominique Martinet Date: Wed, 4 Jul 2018 14:37:41 +0900 Subject: [PATCH] wlr_seat destroy: fix use-after-free when destroying clients wl_resource_for_each_safe isn't safe to use here because it accesses the list's head memory one last time at the end of the loop. Work around this by breaking out early. ==19880==ERROR: AddressSanitizer: heap-use-after-free on address 0x60d0000e6368 at pc 0x7fab68619de2 bp 0x7ffd5c91cee0 sp 0x7ffd5c91ced0 READ of size 8 at 0x60d0000e6368 thread T0 #0 0x7fab68619de1 in wlr_seat_destroy ../types/seat/wlr_seat.c:179 #1 0x7fab68619fb9 in handle_display_destroy ../types/seat/wlr_seat.c:196 #2 0x7fab688e4f8f in wl_priv_signal_emit src/wayland-server.c:2024 #3 0x7fab688e56ca in wl_display_destroy src/wayland-server.c:1092 #4 0x40c11e in server_fini ../sway/server.c:138 #5 0x40b1a8 in main ../sway/main.c:438 #6 0x7fab67b5e18a in __libc_start_main ../csu/libc-start.c:308 #7 0x409359 in _start (/opt/wayland/bin/sway+0x409359) 0x60d0000e6368 is located 24 bytes inside of 144-byte region [0x60d0000e6350,0x60d0000e63e0) freed by thread T0 here: #0 0x7fab6a7d6880 in __interceptor_free (/lib64/libasan.so.5+0xee880) #1 0x7fab68619805 in seat_client_handle_resource_destroy ../types/seat/wlr_seat.c:97 #2 0x7fab688e5025 in destroy_resource src/wayland-server.c:688 previously allocated by thread T0 here: #0 0x7fab6a7d6e50 in calloc (/lib64/libasan.so.5+0xeee50) #1 0x7fab686198df in seat_handle_bind ../types/seat/wlr_seat.c:127 #2 0x7fab6530503d in ffi_call_unix64 (/lib64/libffi.so.6+0x603d) --- types/seat/wlr_seat.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/types/seat/wlr_seat.c b/types/seat/wlr_seat.c index c9eecef6..3c415483 100644 --- a/types/seat/wlr_seat.c +++ b/types/seat/wlr_seat.c @@ -175,10 +175,18 @@ void wlr_seat_destroy(struct wlr_seat *seat) { struct wlr_seat_client *client, *tmp; wl_list_for_each_safe(client, tmp, &seat->clients, link) { - struct wl_resource *resource, *next_resource; - wl_resource_for_each_safe(resource, next_resource, &client->wl_resources) { + struct wl_resource *resource, *next; + /* wl_resource_for_each_safe isn't safe to use here, because the last + * wl_resource_destroy will also destroy the head we cannot do the last + * 'next' update that usually is harmless here. + * Work around this by breaking one step ahead + */ + wl_resource_for_each_safe(resource, next, &client->wl_resources) { // will destroy other resources as well wl_resource_destroy(resource); + if (wl_resource_get_link(next) == &client->wl_resources) { + break; + } } }