[PATCH 3.10 44/58] aio: restore locking of ioctx list on removal

Greg Kroah-Hartman
2013-12-06T21:53:51Z

From: Mateusz Guzik <mguzik@redhat.com>

Commit 36f5588905c10a8c4568a210d601fe8c3c27e0f0
"aio: refcounting cleanup" resulted in ioctx_lock not being held
during ctx removal, leaving the list susceptible to corruptions.

In mainline kernel the issue went away as a side effect of
db446a08c23d5475e6b08c87acca79ebb20f283c "aio: convert the ioctx list to
table lookup v3".

Fix the problem by restoring appropriate locking.

Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Reported-by: Eryu Guan <eguan@redhat.com>
Cc: Jeff Moyer <jmoyer@redhat.com>
Cc: Kent Overstreet <kmo@daterainc.com>
Acked-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/aio.c | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)

--- a/fs/aio.c
+++ b/fs/aio.c
@@ -423,10 +423,12 @@ static void kill_ioctx_rcu(struct rcu_he
* when the processes owning a context have all exited to encourage
* the rapid destruction of the kioctx.
*/
-static void kill_ioctx(struct kioctx *ctx)
+static void kill_ioctx(struct mm_struct *mm, struct kioctx *ctx)
{
if (!atomic_xchg(&ctx->dead, 1)) {
+ spin_lock(&mm->ioctx_lock);
hlist_del_rcu(&ctx->list);
+ spin_unlock(&mm->ioctx_lock);

/*
* It'd be more correct to do this in free_ioctx(), after all
@@ -494,7 +496,7 @@ void exit_aio(struct mm_struct *mm)
*/
ctx->mmap_size = 0;

- kill_ioctx(ctx);
+ kill_ioctx(mm, ctx);
}
}

@@ -852,7 +854,7 @@ SYSCALL_DEFINE2(io_setup, unsigned, nr_e
if (!IS_ERR(ioctx)) {
ret = put_user(ioctx->user_id, ctxp);
if (ret)
- kill_ioctx(ioctx);
+ kill_ioctx(current->mm, ioctx);
put_ioctx(ioctx);
}

@@ -870,7 +872,7 @@ SYSCALL_DEFINE1(io_destroy, aio_context_
{
struct kioctx *ioctx = lookup_ioctx(ctx);
if (likely(NULL != ioctx)) {
- kill_ioctx(ioctx);
+ kill_ioctx(current->mm, ioctx);
put_ioctx(ioctx);
return 0;
}