On Mon, Jul 08, 2019 at 01:04:59PM +0100, Daniel P. Berrangé wrote: > On Mon, Jul 08, 2019 at 01:12:06PM +0200, Michal Privoznik wrote: > > On 7/8/19 12:39 PM, Daniel P. Berrangé wrote: > > > Neither the sasl_client_init or sasl_server_init methods are even > > > remotely threadsafe. They do a bunch of one-time initialization and > > > merely use a simple integer counter to avoid repeated work, not even > > > using atomic increment/reads on the counter. This can easily race in a > > > threaded program. Protect the calls using a virOnce initializer function > > > which is guaranteed threadsafe at least from libvirt's POV. > > > > > > If the application using libvirt also uses another library that makes > > > use of SASL then the race still exists. It is impossible to fix that > > > fully except in SASL code itself. > > > > > > Signed-off-by: Daniel P. Berrangé <berrange@xxxxxxxxxx> > > > --- > > > src/rpc/virnetsaslcontext.c | 50 ++++++++++++++++++++++++------------- > > > 1 file changed, 33 insertions(+), 17 deletions(-) > > > > Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx> > > > > Thanks Sahid for the report! > > FYI i wrote a simple demo program that can reliably reproduce the problem > in isolation Also tested in my side, the patch well fixed the issue. Thanks Daniel and Michal. s. > Regards, > Daniel > -- > |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| > |: https://libvirt.org -o- https://fstop138.berrange.com :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| > #include <libvirt/libvirt.h> > #include <stdio.h> > #include <pthread.h> > #include <unistd.h> > > > pthread_cond_t condReady; > pthread_cond_t condRun; > pthread_mutex_t lock; > int running; > > void *runme(void *arg) > { > virConnectPtr conn; > > pthread_mutex_lock(&lock); > running++; > fprintf(stderr, "Notifying we are ready\n"); > pthread_cond_signal(&condReady); > pthread_cond_wait(&condRun, &lock); > pthread_mutex_unlock(&lock); > fprintf(stderr, "Opening libvirt\n"); > conn = virConnectOpenAuth("qemu:///system", virConnectAuthPtrDefault, 0); > fprintf(stderr, "Open %s\n", conn ? virConnectGetURI(conn) : "failed"); > if (conn) > virConnectClose(conn); > } > > int main(int argc, char **argv) > { > int i; > pthread_t th[20]; > > pthread_mutex_init(&lock, NULL); > pthread_cond_init(&condRun, NULL); > pthread_cond_init(&condReady, NULL); > > for (i = 0; i < 20; i++) { > pthread_create(&th[i], NULL, runme, NULL); > } > > fprintf(stderr, "Waiting for threads to initialize\n"); > pthread_mutex_lock(&lock); > while (running != 20) > pthread_cond_wait(&condReady, &lock); > fprintf(stderr, "Telling threads to proceed\n"); > pthread_cond_broadcast(&condRun); > pthread_mutex_unlock(&lock); > > for (i = 0; i < 20; i++) { > pthread_join(th[i], NULL); > } > return 0; > } -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
