linux-kernel - Re: [PATCH] net: farsync: Fix kmemleak when rmmods farsync

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Message-ID: <Y5HcKlwQuzhpzZs9@nanopsycho>
Date:   Thu, 8 Dec 2022 13:44:26 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Li Zetao <lizetao1@...wei.com>
Cc:     kevin.curtis@...site.co.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: farsync: Fix kmemleak when rmmods farsync

Thu, Dec 08, 2022 at 01:05:40PM CET, lizetao1@...wei.com wrote:
>There are two memory leaks reported by kmemleak:
>
>  unreferenced object 0xffff888114b20200 (size 128):
>    comm "modprobe", pid 4846, jiffies 4295146524 (age 401.345s)
>    hex dump (first 32 bytes):
>      e0 62 57 09 81 88 ff ff e0 62 57 09 81 88 ff ff  .bW......bW.....
>      01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<ffffffff815bcd82>] kmalloc_trace+0x22/0x60
>      [<ffffffff83d35c78>] __hw_addr_add_ex+0x198/0x6c0
>      [<ffffffff83d3989d>] dev_addr_init+0x13d/0x230
>      [<ffffffff83d1063d>] alloc_netdev_mqs+0x10d/0xe50
>      [<ffffffff82b4a06e>] alloc_hdlcdev+0x2e/0x80
>      [<ffffffffa016a741>] fst_add_one+0x601/0x10e0 [farsync]
>      ...
>
>  unreferenced object 0xffff88810b85b000 (size 1024):
>    comm "modprobe", pid 4846, jiffies 4295146523 (age 401.346s)
>    hex dump (first 32 bytes):
>      00 00 b0 02 00 c9 ff ff 00 70 0a 00 00 c9 ff ff  .........p......
>      00 00 00 f2 00 00 00 f3 0a 00 00 00 02 00 00 00  ................
>    backtrace:
>      [<ffffffff815bcd82>] kmalloc_trace+0x22/0x60
>      [<ffffffffa016a294>] fst_add_one+0x154/0x10e0 [farsync]
>      [<ffffffff82060e83>] local_pci_probe+0xd3/0x170
>      ...
>
>The root cause is traced to the netdev and fst_card_info are not freed
>when removes one fst in fst_remove_one(), which may trigger oom if
>repeated insmod and rmmod module.
>
>Fix it by adding free_netdev() and kfree() in fst_remove_one(), just as
>the operations on the error handling path in fst_add_one().
>
>Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
>Signed-off-by: Li Zetao <lizetao1@...wei.com>

Reviewed-by: Jiri Pirko <jiri@...dia.com>

On top, may be worth ordering the cleanup in fst_remove_one() to be
aligned with the order in fst_add_one() error path.