From: Benjamin LaHaise <bcrl@xxxxxxxxx>
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 issue was uncovered as part of CVE-2014-0206.
[jmoyer@xxxxxxxxxx: backported to 3.10]
Signed-off-by: Benjamin LaHaise <bcrl@xxxxxxxxx>
Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Cc: Mateusz Guzik <mguzik@xxxxxxxxxx>
Cc: Petr Matousek <pmatouse@xxxxxxxxxx>
---
aio.c | 4 +---
1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index ebd06fd..8d2c997 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -310,7 +310,6 @@ static void free_ioctx(struct kioctx *ctx)
avail = (head <= ctx->tail ? ctx->tail : ctx->nr_events) - head;
- atomic_sub(avail, &ctx->reqs_active);
head += avail;
head %= ctx->nr_events;
}
@@ -678,6 +677,7 @@ void aio_complete(struct kiocb *iocb, long res, long res2)
put_rq:
/* everything turned out well, dispose of the aiocb. */
aio_put_req(iocb);
+ atomic_dec(&ctx->reqs_active);
/*
* We have to order our ring_info tail store above and test
@@ -755,8 +755,6 @@ 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, ctx->tail);
-
- atomic_sub(ret, &ctx->reqs_active);
out:
mutex_unlock(&ctx->ring_lock);
--
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