Re: [PATCH v3] teamd: stop iterating callbacks when a loop restart is requested
Mon, Oct 10, 2022 at 06:37:31PM CEST, lkundrak(a)v3.sk wrote:
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=<synthetic pointer>,
ctx=<optimized out>) at
/usr/src/debug/libteam-1.31-14.el9.x86_64/teamd/teamd.c:1557
#3 main (argc=<optimized out>, argv=<optimized out>) 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 <lkundrak(a)v3.sk>
Applied, thanks.