Seth Jenkins <sethjenkins@xxxxxxxxxx> writes:
> 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.
>
> Fixes: e4a0d3e720e7 ("aio: Make it possible to remap aio ring")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Seth Jenkins <sethjenkins@xxxxxxxxxx>
> ---
> fs/aio.c | 20 +++++++++++---------
> 1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/fs/aio.c b/fs/aio.c
> index 5b2ff20ad322..74eae7de7323 100644
> --- a/fs/aio.c
> +++ b/fs/aio.c
> @@ -361,16 +361,18 @@ static int aio_ring_mremap(struct vm_area_struct *vma)
> spin_lock(&mm->ioctx_lock);
> rcu_read_lock();
> table = rcu_dereference(mm->ioctx_table);
> - for (i = 0; i < table->nr; i++) {
> - struct kioctx *ctx;
> -
> - ctx = rcu_dereference(table->table[i]);
> - if (ctx && ctx->aio_ring_file == file) {
> - if (!atomic_read(&ctx->dead)) {
> - ctx->user_id = ctx->mmap_base = vma->vm_start;
> - res = 0;
> + if (table) {
> + for (i = 0; i < table->nr; i++) {
> + struct kioctx *ctx;
> +
> + ctx = rcu_dereference(table->table[i]);
> + if (ctx && ctx->aio_ring_file == file) {
> + if (!atomic_read(&ctx->dead)) {
> + ctx->user_id = ctx->mmap_base = vma->vm_start;
This is now over 80 columns. I'd prefer it if you would just invert the
NULL pointer check and add a label:
if (!table)
goto out_unlock;
Other than that, it looks good to me.
Cheers,
Jeff
