xfnw/plan9fox
1
0
Fork 0
Code Issues Pull requests Projects Releases Wiki Activity

upas/smtpd: don't call syslog() from the note handler, this can deadlock

Browse source 
when the alarm hits while the process is currently in syslog(), holding
the sl lock, then calling syslog again will deadlock:

/proc/1729193/text:386 plan 9 executable
/sys/lib/acid/port
/sys/lib/acid/386
acid: lstk()
sleep()+0x7 /sys/src/libc/9syscall/sleep.s:5
lock(lk=0x394d8)+0xb7 /sys/src/libc/port/lock.c:25
	i=0x3e8
syslog(logname=0x41c64,cons=0x0,fmt=0x41c6a)+0x2d /sys/src/libc/9sys/syslog.c:60
	err=0x79732f27
	d=0x0
	ctim=0x0
	buf=0x0
	p=0x0
	arg=0x0
	n=0x0
catchalarm(msg=0xdfffc854)+0x7a /sys/src/cmd/upas/smtp/smtpd.c:71
notifier+0x30 /sys/src/libc/port/atnotify.c:15
This commit is contained in:
cinap_lenrek 2017-10-23 06:08:18 +02:00
parent e3d8fe9d4a
commit 83fe7aaa5c
1 changed files with 1 additions and 12 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
sys/src/cmd/upas/smtp/smtpd.c
View file

@ -55,23 +55,12 @@ static int
catchalarm(void*, char *msg)
{
int ign;
static int chattycathy;
ign = strstr(msg, "closed pipe") != nil;
if(ign)
return 0;
if(chattycathy++ < 5){
if(senders.first && rcvers.first)
syslog(0, "smtpd", "note: %s->%s: %s",
s_to_c(senders.first->p),
s_to_c(rcvers.first->p), msg);
else
syslog(0, "smtpd", "note: %s", msg);
}
if(pp){
if(pp)
syskill(pp->pid);
// pp = 0;
}
return strstr(msg, "alarm") != nil;
}