Re: [PATCH] io_uring: fix memleak in io_init_wq_offload()

[Jens Axboe]

On 7/20/21 2:38 AM, Yang Yingliang wrote:
> I got memory leak report when doing fuzz test:
> 
> BUG: memory leak
> unreferenced object 0xffff888107310a80 (size 96):
> comm "syz-executor.6", pid 4610, jiffies 4295140240 (age 20.135s)
> hex dump (first 32 bytes):
> 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 00 00 00 00 ad 4e ad de ff ff ff ff 00 00 00 00 .....N..........
> backtrace:
> [<000000001974933b>] kmalloc include/linux/slab.h:591 [inline]
> [<000000001974933b>] kzalloc include/linux/slab.h:721 [inline]
> [<000000001974933b>] io_init_wq_offload fs/io_uring.c:7920 [inline]
> [<000000001974933b>] io_uring_alloc_task_context+0x466/0x640 fs/io_uring.c:7955
> [<0000000039d0800d>] __io_uring_add_tctx_node+0x256/0x360 fs/io_uring.c:9016
> [<000000008482e78c>] io_uring_add_tctx_node fs/io_uring.c:9052 [inline]
> [<000000008482e78c>] __do_sys_io_uring_enter fs/io_uring.c:9354 [inline]
> [<000000008482e78c>] __se_sys_io_uring_enter fs/io_uring.c:9301 [inline]
> [<000000008482e78c>] __x64_sys_io_uring_enter+0xabc/0xc20 fs/io_uring.c:9301
> [<00000000b875f18f>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
> [<00000000b875f18f>] do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
> [<000000006b0a8484>] entry_SYSCALL_64_after_hwframe+0x44/0xae
> 
> CPU0                          CPU1
> io_uring_enter                io_uring_enter
> io_uring_add_tctx_node        io_uring_add_tctx_node
> __io_uring_add_tctx_node      __io_uring_add_tctx_node
> io_uring_alloc_task_context   io_uring_alloc_task_context
> io_init_wq_offload            io_init_wq_offload
> hash = kzalloc                hash = kzalloc
> ctx->hash_map = hash          ctx->hash_map = hash <- one of the hash is leaked
> 
> When calling io_uring_enter() in parallel, the 'hash_map' will be leaked, 
> add uring_lock to protect 'hash_map'.

Good catch! Applied, thanks.

-- 
Jens Axboe