Stop using storage after free

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Kevin Coffman <kwc@citi.umich.edu>
The previous patch seems to expose a use after free bug in dirscancb. At
least, I could reliably reproduce a segfault by doing a bunch of mounts
and then unmounting them all. The code uses the following list macro:

      TAILQ_FOREACH(ic, icq, ic_next) {

...to iterate over all of the ic entries and clean up any that no longer
have a corresponding directory in rpc_pipefs. This macro unrolls into:

      for(ic=icq->tqh_first; ic != NULL; ic=ic->ic_next.tqe_next) {

...but within this loop, we can free ic, and then the for loop can trip
over that when it tries to do the iteration. The attached patch works
around this by not using the TAILQ_FOREACH macro and saving off the
tqe_next pointer prior to the free.

Again, this was tested on a patched 1.0.6, but the 1.0.10 code is very
similar, and I think the problem exists there as well.
Signed-off-by: Neil Brown <neilb@suse.de>

diff --git a/utils/idmapd/idmapd.c b/utils/idmapd/idmapd.c
index cbb0b6afe03d029ffcbe47286f88c618ea3b4408..b30b69eb72fb04b7555c5086be2adb5f84f72501 100644 (file)
--- a/utils/idmapd/idmapd.c
+++ b/utils/idmapd/idmapd.c
@@ -444,7 +444,7 @@ dirscancb(int fd, short which, void *data)
 {
        int nent, i;
        struct dirent **ents;
-       struct idmap_client *ic;
+       struct idmap_client *ic, *nextic;
        char path[PATH_MAX];
        struct idmap_clientq *icq = data;
 
@@ -498,7 +498,9 @@ dirscancb(int fd, short which, void *data)
                }
        }
 
-       TAILQ_FOREACH(ic, icq, ic_next) {
+       ic = TAILQ_FIRST(icq);
+       while(ic != NULL) {
+               nextic=TAILQ_NEXT(ic, ic_next);
                if (!ic->ic_scanned) {
                        event_del(&ic->ic_event);
                        close(ic->ic_fd);
@@ -511,6 +513,7 @@ dirscancb(int fd, short which, void *data)
                        free(ic);
                } else
                        ic->ic_scanned = 0;
+               ic = nextic;
        }
 
 out: