From: Neil Horman nhorman@tuxdriver.com
[ Upstream commit 20a785aa52c82246055a089e55df9dac47d67da1 ]
This BUG halt was reported a while back, but the patch somehow got missed:
PID: 2879 TASK: c16adaa0 CPU: 1 COMMAND: "sctpn" #0 [f418dd28] crash_kexec at c04a7d8c #1 [f418dd7c] oops_end at c0863e02 #2 [f418dd90] do_invalid_op at c040aaca #3 [f418de28] error_code (via invalid_op) at c08631a5 EAX: f34baac0 EBX: 00000090 ECX: f418deb0 EDX: f5542950 EBP: 00000000 DS: 007b ESI: f34ba800 ES: 007b EDI: f418dea0 GS: 00e0 CS: 0060 EIP: c046fa5e ERR: ffffffff EFLAGS: 00010286 #4 [f418de5c] add_timer at c046fa5e #5 [f418de68] sctp_do_sm at f8db8c77 [sctp] #6 [f418df30] sctp_primitive_SHUTDOWN at f8dcc1b5 [sctp] #7 [f418df48] inet_shutdown at c080baf9 #8 [f418df5c] sys_shutdown at c079eedf #9 [f418df70] sys_socketcall at c079fe88 EAX: ffffffda EBX: 0000000d ECX: bfceea90 EDX: 0937af98 DS: 007b ESI: 0000000c ES: 007b EDI: b7150ae4 SS: 007b ESP: bfceea7c EBP: bfceeaa8 GS: 0033 CS: 0073 EIP: b775c424 ERR: 00000066 EFLAGS: 00000282
It appears that the side effect that starts the shutdown timer was processed multiple times, which can happen as multiple paths can trigger it. This of course leads to the BUG halt in add_timer getting called.
Fix seems pretty straightforward, just check before the timer is added if its already been started. If it has mod the timer instead to min(current expiration, new expiration)
Its been tested but not confirmed to fix the problem, as the issue has only occured in production environments where test kernels are enjoined from being installed. It appears to be a sane fix to me though. Also, recentely, Jere found a reproducer posted on list to confirm that this resolves the issues
Signed-off-by: Neil Horman nhorman@tuxdriver.com CC: Vlad Yasevich vyasevich@gmail.com CC: "David S. Miller" davem@davemloft.net CC: jere.leppanen@nokia.com CC: marcelo.leitner@gmail.com CC: netdev@vger.kernel.org Acked-by: Marcelo Ricardo Leitner marcelo.leitner@gmail.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sctp/sm_sideeffect.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/net/sctp/sm_sideeffect.c b/net/sctp/sm_sideeffect.c index 2bc29463e1dc..9f36fe911d08 100644 --- a/net/sctp/sm_sideeffect.c +++ b/net/sctp/sm_sideeffect.c @@ -1523,9 +1523,17 @@ static int sctp_cmd_interpreter(enum sctp_event_type event_type, timeout = asoc->timeouts[cmd->obj.to]; BUG_ON(!timeout);
- timer->expires = jiffies + timeout; - sctp_association_hold(asoc); - add_timer(timer); + /* + * SCTP has a hard time with timer starts. Because we process + * timer starts as side effects, it can be hard to tell if we + * have already started a timer or not, which leads to BUG + * halts when we call add_timer. So here, instead of just starting + * a timer, if the timer is already started, and just mod + * the timer with the shorter of the two expiration times + */ + if (!timer_pending(timer)) + sctp_association_hold(asoc); + timer_reduce(timer, jiffies + timeout); break;
case SCTP_CMD_TIMER_RESTART: