From: Seth Jenkins <sethjenkins@xxxxxxxxxx>
commit 81e9d6f8647650a7bead74c5f926e29970e834d1 upstream.
Commit e4a0d3e720e7 ("aio: Make it possible to remap aio ring") introduced
a null-deref if mremap is called on an old aio mapping after fork as
mm->ioctx_table will be set to NULL.
[jmoyer@xxxxxxxxxx: fix 80 column issue]
Link: https://lkml.kernel.org/r/x49sffq4nvg.fsf@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: e4a0d3e720e7 ("aio: Make it possible to remap aio ring")
Signed-off-by: Seth Jenkins <sethjenkins@xxxxxxxxxx>
Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Benjamin LaHaise <bcrl@xxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/aio.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -336,6 +336,9 @@ static int aio_ring_mremap(struct vm_are
spin_lock(&mm->ioctx_lock);
rcu_read_lock();
table = rcu_dereference(mm->ioctx_table);
+ if (!table)
+ goto out_unlock;
+
for (i = 0; i < table->nr; i++) {
struct kioctx *ctx;
@@ -349,6 +352,7 @@ static int aio_ring_mremap(struct vm_are
}
}
+out_unlock:
rcu_read_unlock();
spin_unlock(&mm->ioctx_lock);
return res;
