aio: fix aio request leak when events are reaped by userspace

commit f8567a3845ac05bb28f3c1b478ef752762bd39ef upstream.

The aio cleanups and optimizations by kmo that were merged into the 3.10
tree added a regression for userspace event reaping.  Specifically, the
reference counts are not decremented if the event is reaped in userspace,
leading to the application being unable to submit further aio requests.
This patch applies to 3.12+.  A separate backport is required for 3.10/3.11.
This issue was uncovered as part of CVE-2014-0206.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Cc: Kent Overstreet <kmo@daterainc.com>
Cc: Mateusz Guzik <mguzik@redhat.com>
Cc: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/fs/aio.c b/fs/aio.c
index 04cd7686555d3fe9c3c8ee642211630837a4ba0e..e9566f2ba4dfbbc3d11f871e14358447a2e6f9cd 100644 (file)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1007,6 +1007,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
 
        /* everything turned out well, dispose of the aiocb. */
        kiocb_free(iocb);
+       put_reqs_available(ctx, 1);
 
        /*
         * We have to order our ring_info tail store above and test
@@ -1086,8 +1087,6 @@ static long aio_read_events_ring(struct kioctx *ctx,
        flush_dcache_page(ctx->ring_pages[0]);
 
        pr_debug("%li  h%u t%u\n", ret, head, tail);
-
-       put_reqs_available(ctx, ret);
 out:
        mutex_unlock(&ctx->ring_lock);