linux-kernel - Re: [PATCH v2] cgroup: Fix memory leak when parsing multiple source parameters

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Date:   Wed, 16 Dec 2020 10:11:36 -0500
From:   Tejun Heo <tj@...nel.org>
To:     Qinglang Miao <miaoqinglang@...wei.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] cgroup: Fix memory leak when parsing multiple source
 parameters

On Thu, Dec 10, 2020 at 09:29:43AM +0800, Qinglang Miao wrote:
> A memory leak is found in cgroup1_parse_param() when multiple source
> parameters overwrite fc->source in the fs_context struct without free.
> 
> unreferenced object 0xffff888100d930e0 (size 16):
>   comm "mount", pid 520, jiffies 4303326831 (age 152.783s)
>   hex dump (first 16 bytes):
>     74 65 73 74 6c 65 61 6b 00 00 00 00 00 00 00 00  testleak........
>   backtrace:
>     [<000000003e5023ec>] kmemdup_nul+0x2d/0xa0
>     [<00000000377dbdaa>] vfs_parse_fs_string+0xc0/0x150
>     [<00000000cb2b4882>] generic_parse_monolithic+0x15a/0x1d0
>     [<000000000f750198>] path_mount+0xee1/0x1820
>     [<0000000004756de2>] do_mount+0xea/0x100
>     [<0000000094cafb0a>] __x64_sys_mount+0x14b/0x1f0
> 
> Fix this bug by permitting a single source parameter and rejecting with
> an error all subsequent ones.
> 
> Fixes: 8d2451f4994f ("cgroup1: switch to option-by-option parsing")
> Reported-by: Hulk Robot <hulkci@...wei.com>
> Signed-off-by: Qinglang Miao <miaoqinglang@...wei.com>

Applied to cgroup/for-5.11.

Thanks.

-- 
tejun