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Subject: Re: [PATCH] io_uring: fix memleak in __io_sqe_files_update()
To:     Yang Yingliang <yangyingliang@huawei.com>,
        io-uring@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20200709101141.3261977-1-yangyingliang@huawei.com>
From:   Jens Axboe <axboe@kernel.dk>
Message-ID: <1edf6ed7-690e-ef7d-df35-b5d7f5bc6cb4@kernel.dk>
Date:   Wed, 8 Jul 2020 20:16:54 -0600
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On 7/9/20 4:11 AM, Yang Yingliang wrote:
> I got a memleak report when doing some fuzz test:
> 
> BUG: memory leak
> unreferenced object 0xffff888113e02300 (size 488):
> comm "syz-executor401", pid 356, jiffies 4294809529 (age 11.954s)
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> a0 a4 ce 19 81 88 ff ff 60 ce 09 0d 81 88 ff ff ........`.......
> backtrace:
> [<00000000129a84ec>] kmem_cache_zalloc include/linux/slab.h:659 [inline]
> [<00000000129a84ec>] __alloc_file+0x25/0x310 fs/file_table.c:101
> [<000000003050ad84>] alloc_empty_file+0x4f/0x120 fs/file_table.c:151
> [<000000004d0a41a3>] alloc_file+0x5e/0x550 fs/file_table.c:193
> [<000000002cb242f0>] alloc_file_pseudo+0x16a/0x240 fs/file_table.c:233
> [<00000000046a4baa>] anon_inode_getfile fs/anon_inodes.c:91 [inline]
> [<00000000046a4baa>] anon_inode_getfile+0xac/0x1c0 fs/anon_inodes.c:74
> [<0000000035beb745>] __do_sys_perf_event_open+0xd4a/0x2680 kernel/events/core.c:11720
> [<0000000049009dc7>] do_syscall_64+0x56/0xa0 arch/x86/entry/common.c:359
> [<00000000353731ca>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> BUG: memory leak
> unreferenced object 0xffff8881152dd5e0 (size 16):
> comm "syz-executor401", pid 356, jiffies 4294809529 (age 11.954s)
> hex dump (first 16 bytes):
> 01 00 00 00 01 00 00 00 00 00 00 00 00 00 00 00 ................
> backtrace:
> [<0000000074caa794>] kmem_cache_zalloc include/linux/slab.h:659 [inline]
> [<0000000074caa794>] lsm_file_alloc security/security.c:567 [inline]
> [<0000000074caa794>] security_file_alloc+0x32/0x160 security/security.c:1440
> [<00000000c6745ea3>] __alloc_file+0xba/0x310 fs/file_table.c:106
> [<000000003050ad84>] alloc_empty_file+0x4f/0x120 fs/file_table.c:151
> [<000000004d0a41a3>] alloc_file+0x5e/0x550 fs/file_table.c:193
> [<000000002cb242f0>] alloc_file_pseudo+0x16a/0x240 fs/file_table.c:233
> [<00000000046a4baa>] anon_inode_getfile fs/anon_inodes.c:91 [inline]
> [<00000000046a4baa>] anon_inode_getfile+0xac/0x1c0 fs/anon_inodes.c:74
> [<0000000035beb745>] __do_sys_perf_event_open+0xd4a/0x2680 kernel/events/core.c:11720
> [<0000000049009dc7>] do_syscall_64+0x56/0xa0 arch/x86/entry/common.c:359
> [<00000000353731ca>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> If io_sqe_file_register() failed, we need put the file that get by fget()
> to avoid the memleak.
> 
> Fixes: c3a31e605620 ("io_uring: add support for IORING_REGISTER_FILES_UPDATE")
> Reported-by: Hulk Robot <hulkci@huawei.com>
> Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
> ---
>  fs/io_uring.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index e507737f044e..5c2487d954b2 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -6814,8 +6814,10 @@ static int __io_sqe_files_update(struct io_ring_ctx *ctx,
>  			}
>  			table->files[index] = file;
>  			err = io_sqe_file_register(ctx, file, i);
> -			if (err)
> +			if (err) {
> +				fput(file);
>  				break;
> +			}
>  		}
>  		nr_args--;
>  		done++;

Thanks, this looks good. I've committed it and marked it for stable
as well.

-- 
Jens Axboe