History

io_uring/nop: fix file reference leak with IOSQE_FIXED_FILE

NOP file-acquisition support choses between a fixed (registered) file and a normal fget()'d file based on its own IORING_NOP_FIXED_FILE flag in sqe->nop_flags. However, a request's REQ_F_FIXED_FILE is set independently from the generic IOSQE_FIXED_FILE sqe flag during request init, before the issue handler runs. If a NOP is submitted with IOSQE_FIXED_FILE set (so REQ_F_FIXED_FILE is set) but without IORING_NOP_FIXED_FILE, io_nop() takes the normal path and grabs a real reference via io_file_get_normal(). On completion, io_put_file() only drops the reference when REQ_F_FIXED_FILE is clear, so the fget()'d file is never released and leaks: BUG: memory leak unreferenced object 0xffff88800f42c240 (size 176): kmem_cache_alloc_noprof+0x358/0x440 alloc_empty_file+0x57/0x180 path_openat+0x44/0x1e50 do_file_open+0x121/0x200 do_sys_openat2+0xa7/0x150 __x64_sys_openat+0x82/0xf0 Decide between fixed and normal file acquisition from REQ_F_FIXED_FILE, the same way io_assign_file() does for every other opcode, and fold IORING_NOP_FIXED_FILE into REQ_F_FIXED_FILE at prep time.

Vasileios Almpanis committed 4 months ago

Commit 2564ca21 parent 8b308f91 file · +4 −4Browse files

Unified · Split

io_uring/nop.c+4−4
@@ -40,6 +40,8 @@ int io_nop_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe) · 39 unmodified lines
40 nop->fd = READ_ONCE(sqe->fd);40 nop->fd = READ_ONCE(sqe->fd);
41 else41 else
42 nop->fd = -1;42 nop->fd = -1;
43 if (nop->flags & IORING_NOP_FIXED_FILE)
44 req->flags |= REQ_F_FIXED_FILE;
43 if (nop->flags & IORING_NOP_FIXED_BUFFER)45 if (nop->flags & IORING_NOP_FIXED_BUFFER)
44 req->buf_index = READ_ONCE(sqe->buf_index);46 req->buf_index = READ_ONCE(sqe->buf_index);
45 if (nop->flags & IORING_NOP_CQE32) {47 if (nop->flags & IORING_NOP_CQE32) {
@@ -59,12 +61,10 @@ int io_nop(struct io_kiocb *req, unsigned int issue_flags) · 13 unmodified lines
59 int ret = nop->result;61 int ret = nop->result;
60 62
61 if (nop->flags & IORING_NOP_FILE) {63 if (nop->flags & IORING_NOP_FILE) {
62 if (nop->flags & IORING_NOP_FIXED_FILE) {64 if (req->flags & REQ_F_FIXED_FILE)
63 req->file = io_file_get_fixed(req, nop->fd, issue_flags);65 req->file = io_file_get_fixed(req, nop->fd, issue_flags);
64 req->flags |= REQ_F_FIXED_FILE;66 else
65 } else {
66 req->file = io_file_get_normal(req, nop->fd);67 req->file = io_file_get_normal(req, nop->fd);
67 }
68 if (!req->file) {68 if (!req->file) {
69 ret = -EBADF;69 ret = -EBADF;
70 goto done;70 goto done;