linux-kernel - Re: [PATCH v2] vdpa_sim: fix possible memory leak in vdpasim_net_init() and vdpasim_blk

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Message-ID: <20221110080147.bpfumiab2yt7nehf@sgarzare-redhat>
Date:   Thu, 10 Nov 2022 09:01:47 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     ruanjinjie <ruanjinjie@...wei.com>
Cc:     mst@...hat.com, jasowang@...hat.com, eperezma@...hat.com,
        gautam.dawar@...inx.com, elic@...dia.com,
        virtualization@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vdpa_sim: fix possible memory leak in
 vdpasim_net_init() and vdpasim_blk_init()

Hi,

On Thu, Nov 10, 2022 at 01:04:46PM +0800, ruanjinjie wrote:
>Inject fault while probing module, if device_register() fails in
>vdpasim_net_init() or vdpasim_blk_init(), but the refcount of kobject is
>not decreased to 0, the name allocated in dev_set_name() is leaked.
>Fix this by calling put_device(), so that name can be freed in
>callback function kobject_cleanup().
>
>(vdpa_sim_net)
>unreferenced object 0xffff88807eebc370 (size 16):
>  comm "modprobe", pid 3848, jiffies 4362982860 (age 18.153s)
>  hex dump (first 16 bytes):
>    76 64 70 61 73 69 6d 5f 6e 65 74 00 6b 6b 6b a5  vdpasim_net.kkk.
>  backtrace:
>    [<ffffffff8174f19e>] __kmalloc_node_track_caller+0x4e/0x150
>    [<ffffffff81731d53>] kstrdup+0x33/0x60
>    [<ffffffff83a5d421>] kobject_set_name_vargs+0x41/0x110
>    [<ffffffff82d87aab>] dev_set_name+0xab/0xe0
>    [<ffffffff82d91a23>] device_add+0xe3/0x1a80
>    [<ffffffffa0270013>] 0xffffffffa0270013
>    [<ffffffff81001c27>] do_one_initcall+0x87/0x2e0
>    [<ffffffff813739cb>] do_init_module+0x1ab/0x640
>    [<ffffffff81379d20>] load_module+0x5d00/0x77f0
>    [<ffffffff8137bc40>] __do_sys_finit_module+0x110/0x1b0
>    [<ffffffff83c4d505>] do_syscall_64+0x35/0x80
>    [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
>(vdpa_sim_blk)
>unreferenced object 0xffff8881070c1250 (size 16):
>  comm "modprobe", pid 6844, jiffies 4364069319 (age 17.572s)
>  hex dump (first 16 bytes):
>    76 64 70 61 73 69 6d 5f 62 6c 6b 00 6b 6b 6b a5  vdpasim_blk.kkk.
>  backtrace:
>    [<ffffffff8174f19e>] __kmalloc_node_track_caller+0x4e/0x150
>    [<ffffffff81731d53>] kstrdup+0x33/0x60
>    [<ffffffff83a5d421>] kobject_set_name_vargs+0x41/0x110
>    [<ffffffff82d87aab>] dev_set_name+0xab/0xe0
>    [<ffffffff82d91a23>] device_add+0xe3/0x1a80
>    [<ffffffffa0220013>] 0xffffffffa0220013
>    [<ffffffff81001c27>] do_one_initcall+0x87/0x2e0
>    [<ffffffff813739cb>] do_init_module+0x1ab/0x640
>    [<ffffffff81379d20>] load_module+0x5d00/0x77f0
>    [<ffffffff8137bc40>] __do_sys_finit_module+0x110/0x1b0
>    [<ffffffff83c4d505>] do_syscall_64+0x35/0x80
>    [<ffffffff83e0006a>] entry_SYSCALL_64_after_hwframe+0x46/0xb0
>
>Signed-off-by: ruanjinjie <ruanjinjie@...wei.com>
>---
>v2:
>- add fault inject message
>---
> drivers/vdpa/vdpa_sim/vdpa_sim_blk.c | 4 +++-
> drivers/vdpa/vdpa_sim/vdpa_sim_net.c | 4 +++-
> 2 files changed, 6 insertions(+), 2 deletions(-)

Thanks for the v2 of this patch!
It LGTM, just a couple of comments about the submit process.

Usually when you get A-b R-b's and the patch doesn't change, it's better 
to bring them in later versions.

Also, we had suggested reporting the Fixes tag, because usually when we 
fix a bug it's good to identify which patch introduced the problem, so 
it's easier to backport this fix into stable versions of the kernel.
https://www.kernel.org/doc/html/v4.17/process/submitting-patches.html#describe-your-changes

In this case we should use the following tags:

Fixes: 899c4d187f6a ("vdpa_sim_blk: add support for vdpa management tool")
Fixes: a3c06ae158dd ("vdpa_sim_net: Add support for user supported devices")

With them:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

Thanks,
Stefano