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io_uring: Fix XArray usage in io_uring_add_task_file

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The xas_store() wasn't paired with an xas_nomem() loop, so if it couldn't
allocate memory using GFP_NOWAIT, it would leak the reference to the file
descriptor.  Also the node pointed to by the xas could be freed between
the call to xas_load() under the rcu_read_lock() and the acquisition of
the xa_lock.

It's easier to just use the normal xa_load/xa_store interface here.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
[axboe: fix missing assign after alloc, cur_uring -> tctx rename]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Matthew Wilcox (Oracle) 2020-10-09 13:49:52 +01:00 committed by Jens Axboe
parent ce765372bc
commit 236434c343
1 changed files with 9 additions and 12 deletions
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21
fs/io_uring.c
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@ -8586,27 +8586,24 @@ static void io_uring_cancel_task_requests(struct io_ring_ctx *ctx,
*/
static int io_uring_add_task_file(struct file *file)
{
if (unlikely(!current->io_uring)) {
struct io_uring_task *tctx = current->io_uring;
if (unlikely(!tctx)) {
int ret;
ret = io_uring_alloc_task_context(current);
if (unlikely(ret))
return ret;
tctx = current->io_uring;
}
if (current->io_uring->last != file) {
XA_STATE(xas, &current->io_uring->xa, (unsigned long) file);
void *old;
if (tctx->last != file) {
void *old = xa_load(&tctx->xa, (unsigned long)file);
rcu_read_lock();
old = xas_load(&xas);
if (old != file) {
if (!old) {
get_file(file);
xas_lock(&xas);
xas_store(&xas, file);
xas_unlock(&xas);
xa_store(&tctx->xa, (unsigned long)file, file, GFP_KERNEL);
}
rcu_read_unlock();
current->io_uring->last = file;
tctx->last = file;
}
return 0;