[PATCH 5.18 066/141] io_uring: fix races with file table unregister

Greg Kroah-Hartman
2022-06-20T13:01:27Z

From: Pavel Begunkov <asml.silence@gmail.com>

[ Upstream commit b0380bf6dad4601d92025841e2b7a135d566c6e3 ]

Fixed file table quiesce might unlock ->uring_lock, potentially letting
new requests to be submitted, don't allow those requests to use the
table as they will race with unregistration.

Reported-and-tested-by: van fantasy <g1042620637@gmail.com>
Fixes: 05f3fb3c53975 ("io_uring: avoid ring quiesce for fixed file set unregister and update")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io_uring.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 3582db014aad..0a9f9000fc80 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -8508,11 +8508,19 @@ static void __io_sqe_files_unregister(struct io_ring_ctx *ctx)

static int io_sqe_files_unregister(struct io_ring_ctx *ctx)
{
+ unsigned nr = ctx->nr_user_files;
int ret;

if (!ctx->file_data)
return -ENXIO;
+
+ /*
+ * Quiesce may unlock ->uring_lock, and while it's not held
+ * prevent new requests using the table.
+ */
+ ctx->nr_user_files = 0;
ret = io_rsrc_ref_quiesce(ctx->file_data, ctx);
+ ctx->nr_user_files = nr;
if (!ret)
__io_sqe_files_unregister(ctx);
return ret;
--
2.35.1