From ffc6a52bd285a476b547312012078af69220574b Mon Sep 17 00:00:00 2001 From: Lubomir Rintel Date: Mon, 10 Oct 2022 18:37:31 +0200 Subject: [PATCH] teamd: stop iterating callbacks when a loop restart is requested A crash was observed: Added loop callback: dbus_watch, 0x560d279e4530 Added loop callback: dbus_watch, 0x560d279e4580 ... Removed loop callback: dbus_watch, 0x560d279e4580 Removed loop callback: dbus_watch, 0x560d279e4530 Aug 31 11:54:11 holaprdel kernel: traps: teamd[557] general protection fault ip:560d26469a55 sp:7ffd43ca9650 error:0 in teamd[560d26463000+16000] Traceback (from a different run than above): Core was generated by `/usr/bin/teamd -o -n -U -D -N -t team0 -gg'. Program terminated with signal SIGSEGV, Segmentation fault. #0 0x00005600ac090a55 in teamd_run_loop_do_callbacks (ctx=0x5600ad9bac70, fds=0x7fff40861250, lcb_list=0x5600ad9bad58) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:321 321 list_for_each_node_entry_safe(lcb, tmp, lcb_list, list) { (gdb) bt #0 0x00005600ac090a55 in teamd_run_loop_do_callbacks (ctx=0x5600ad9bac70, fds=0x7fff40861250, lcb_list=0x5600ad9bad58) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:321 #1 teamd_run_loop_run (ctx=0x5600ad9bac70) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:415 #2 0x00005600ac08d8cb in teamd_start (p_ret=, ctx=) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:1557 #3 main (argc=, argv=) at /usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:1876 (gdb) print *lcb Cannot access memory at address 0x9dd29944fb7e97fc (gdb) print *tmp Cannot access memory at address 0x9dd29944fb7e9804 (gdb) What has happened is that libdbus called the remove_watch callback twice in a single go, causing two callbacks being destroyed in one iteration of teamd_run_loop_do_callbacks()'s list_for_each_node_entry_safe(). This basically turns the _safe() variant of the macro unhelpful, as tmp points to stale data anyway. Let's use the unsafe variant then, and terminate the loop once teamd_loop_callback_del() asks for main loop's attention via teamd_run_loop_restart(). If there are other callbacks pending an action, they will get their turn in the next main loop iteration. Signed-off-by: Lubomir Rintel Signed-off-by: Jiri Pirko --- teamd/teamd.c | 26 ++++++++++++++++++++++++-- 1 file changed, 24 insertions(+), 2 deletions(-) diff --git a/teamd/teamd.c b/teamd/teamd.c index b310140..a89b702 100644 --- a/teamd/teamd.c +++ b/teamd/teamd.c @@ -309,16 +309,28 @@ static void teamd_run_loop_set_fds(struct list_item *lcb_list, } } +static int teamd_check_ctrl(struct teamd_context *ctx) +{ + int ctrl_fd = ctx->run_loop.ctrl_pipe_r; + struct timeval tv; + fd_set rfds; + + FD_ZERO(&rfds); + FD_SET(ctrl_fd, &rfds); + tv.tv_sec = tv.tv_usec = 0; + + return select(ctrl_fd + 1, &rfds, NULL, NULL, &tv); +} + static int teamd_run_loop_do_callbacks(struct list_item *lcb_list, fd_set *fds, struct teamd_context *ctx) { struct teamd_loop_callback *lcb; - struct teamd_loop_callback *tmp; int i; int events; int err; - list_for_each_node_entry_safe(lcb, tmp, lcb_list, list) { + list_for_each_node_entry(lcb, lcb_list, list) { for (i = 0; i < 3; i++) { if (!(lcb->fd_event & (1 << i))) continue; @@ -339,6 +351,16 @@ static int teamd_run_loop_do_callbacks(struct list_item *lcb_list, fd_set *fds, teamd_log_dbg(ctx, "Failed loop callback: %s, %p", lcb->name, lcb->priv); } + + /* + * If there's a control byte ready, it's possible that + * one or more entries have been removed from the + * callback list and restart has been requested. In any + * case, let the main loop deal with it first so that + * we know we're safe to proceed. + */ + if (teamd_check_ctrl(ctx)) + return 0; } } return 0; -- 2.31.1