diff options
| author | Anand Avati <avati@redhat.com> | 2013-03-04 13:22:25 -0800 |
|---|---|---|
| committer | Anand Avati <avati@redhat.com> | 2013-03-07 07:03:26 -0800 |
| commit | 90d77fbdd2c5066279f2c7ddeee0980811ba4923 (patch) | |
| tree | ba6d935dcaae21ae5e07260f011c068f5465a56b /api | |
| parent | ee5df68f08e44451e14c42adc9bc4d38721b5d6c (diff) | |
gfapi: dict_unref() xattr_req in fop finish instead of dict_destroy()
The current way of calling dict_destroy() at the end of an API fop assumes
that xattr_req is not stored/ref'd by any translators in the stack. However
when translators like DHT store xattr_req in dht_local_t with a dict_ref()
and perform dict_unref() in the unwind path, things get subject to a race.
The race is between the woken up thread (by syncop_wake) i.e, the gfapi
invoking thread and the thread where the FOP was unwound. As the C stack
of STACK_UNWIND unwinds back, dht_local_unref() gets invoked within the
DHT_STACK_UNWIND macro. This thread attempts dict_unref, which would
be "safe" if it wins the race against the gfapi invoking thread. However
if the gfapi invoking thread wins the race, it will perform dict_destroy()
first and therefore make dict_unref() within dht_local_unref perform
a double free.
This is the embarrassing on-screen bug which showed up in a roomful of people
during the gluster dev summit demo of qemu/libgfapi integration.
Change-Id: I284c93de87cdc128d5801f42c84aa87f753090d4
BUG: 839950
Signed-off-by: Anand Avati <avati@redhat.com>
Reviewed-on: http://review.gluster.org/4644
Reviewed-by: Jeff Darcy <jdarcy@redhat.com>
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Diffstat (limited to 'api')
| -rw-r--r-- | api/src/glfs-fops.c | 8 | ||||
| -rw-r--r-- | api/src/glfs-resolve.c | 2 |
2 files changed, 5 insertions, 5 deletions
diff --git a/api/src/glfs-fops.c b/api/src/glfs-fops.c index be26dc121de..84d364857fa 100644 --- a/api/src/glfs-fops.c +++ b/api/src/glfs-fops.c @@ -268,7 +268,7 @@ out: loc_wipe (&loc); if (xattr_req) - dict_destroy (xattr_req); + dict_unref (xattr_req); if (ret && glfd) { glfs_fd_destroy (glfd); @@ -953,7 +953,7 @@ out: loc_wipe (&loc); if (xattr_req) - dict_destroy (xattr_req); + dict_unref (xattr_req); return ret; } @@ -1059,7 +1059,7 @@ out: loc_wipe (&loc); if (xattr_req) - dict_destroy (xattr_req); + dict_unref (xattr_req); return ret; } @@ -1130,7 +1130,7 @@ out: loc_wipe (&loc); if (xattr_req) - dict_destroy (xattr_req); + dict_unref (xattr_req); return ret; } diff --git a/api/src/glfs-resolve.c b/api/src/glfs-resolve.c index f7754d2019b..a9b93818637 100644 --- a/api/src/glfs-resolve.c +++ b/api/src/glfs-resolve.c @@ -201,7 +201,7 @@ glfs_resolve_component (struct glfs *fs, xlator_t *subvol, inode_t *parent, *iatt = ciatt; out: if (xattr_req) - dict_destroy (xattr_req); + dict_unref (xattr_req); loc_wipe (&loc); |