[PATCH] io-wq: Fix memory leak in worker creation

[PATCH] io-wq: Fix memory leak in worker creation

[Rafael Mendonca]

If the CPU mask allocation for a node fails, then the memory allocated for
the 'io_wqe' struct of the current node doesn't get freed on the error
handling path, since it has not yet been added to the 'wqes' array.

This was spotted when fuzzing v6.1-rc1 with Syzkaller:
BUG: memory leak
unreferenced object 0xffff8880093d5000 (size 1024):
  comm "syz-executor.2", pid 7701, jiffies 4295048595 (age 13.900s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<00000000cb463369>] __kmem_cache_alloc_node+0x18e/0x720
    [<00000000147a3f9c>] kmalloc_node_trace+0x2a/0x130
    [<000000004e107011>] io_wq_create+0x7b9/0xdc0
    [<00000000c38b2018>] io_uring_alloc_task_context+0x31e/0x59d
    [<00000000867399da>] __io_uring_add_tctx_node.cold+0x19/0x1ba
    [<000000007e0e7a79>] io_uring_setup.cold+0x1b80/0x1dce
    [<00000000b545e9f6>] __x64_sys_io_uring_setup+0x5d/0x80
    [<000000008a8a7508>] do_syscall_64+0x5d/0x90
    [<000000004ac08bec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Fixes: 0e03496d1967 ("io-wq: use private CPU mask")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
---
 io_uring/io-wq.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c
index c6536d4b2da0..6f1d0e5df23a 100644
--- a/io_uring/io-wq.c
+++ b/io_uring/io-wq.c
@@ -1164,10 +1164,10 @@ struct io_wq *io_wq_create(unsigned bounded, struct io_wq_data *data)
 		wqe = kzalloc_node(sizeof(struct io_wqe), GFP_KERNEL, alloc_node);
 		if (!wqe)
 			goto err;
+		wq->wqes[node] = wqe;
 		if (!alloc_cpumask_var(&wqe->cpu_mask, GFP_KERNEL))
 			goto err;
 		cpumask_copy(wqe->cpu_mask, cpumask_of_node(node));
-		wq->wqes[node] = wqe;
 		wqe->node = alloc_node;
 		wqe->acct[IO_WQ_ACCT_BOUND].max_workers = bounded;
 		wqe->acct[IO_WQ_ACCT_UNBOUND].max_workers =
-- 
2.34.1

Re: [PATCH] io-wq: Fix memory leak in worker creation

[Jens Axboe]

On Wed, 19 Oct 2022 22:47:09 -0300, Rafael Mendonca wrote:
> If the CPU mask allocation for a node fails, then the memory allocated for
> the 'io_wqe' struct of the current node doesn't get freed on the error
> handling path, since it has not yet been added to the 'wqes' array.
> 
> This was spotted when fuzzing v6.1-rc1 with Syzkaller:
> BUG: memory leak
> unreferenced object 0xffff8880093d5000 (size 1024):
>   comm "syz-executor.2", pid 7701, jiffies 4295048595 (age 13.900s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<00000000cb463369>] __kmem_cache_alloc_node+0x18e/0x720
>     [<00000000147a3f9c>] kmalloc_node_trace+0x2a/0x130
>     [<000000004e107011>] io_wq_create+0x7b9/0xdc0
>     [<00000000c38b2018>] io_uring_alloc_task_context+0x31e/0x59d
>     [<00000000867399da>] __io_uring_add_tctx_node.cold+0x19/0x1ba
>     [<000000007e0e7a79>] io_uring_setup.cold+0x1b80/0x1dce
>     [<00000000b545e9f6>] __x64_sys_io_uring_setup+0x5d/0x80
>     [<000000008a8a7508>] do_syscall_64+0x5d/0x90
>     [<000000004ac08bec>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
> 
> [...]

Applied, thanks!

[1/1] io-wq: Fix memory leak in worker creation
      commit: 839a0c962971a5a95515c1637aede8a4fbc6547f

Best regards,
-- 
Jens Axboe