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    SubjectRe: [PATCH] nfc: fix memory leak of se_io context in nfc_genl_se_io
    On Tue, Feb 28, 2023 at 11:14:03AM +0100, Krzysztof Kozlowski wrote:
    > On 27/02/2023 16:05, Fedor Pchelkin wrote:
    > >>> Fixes: 5ce3f32b5264 ("NFC: netlink: SE API implementation")
    > >>> Reported-by: syzbot+df64c0a2e8d68e78a4fa@syzkaller.appspotmail.com
    > >>> Signed-off-by: Fedor Pchelkin <pchelkin@ispras.ru>
    > >>> Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
    > >>
    > >> SoB order is a bit odd. Who is the author?
    > >>
    > >
    > > The author is me (Fedor). I thought the authorship is expressed with the
    > > first Signed-off-by line, isn't it?
    >
    > Yes and since you are sending it, then what is Alexey's Sob for? The
    > tags are in order...
    >

    Now I get what you mean. Alexey is my supervisor and the patches I make
    are passed through him (even though they are sent by me). If this is not
    a customary thing, then I'll take that into account for further
    submissions. I guess something like Acked-by is more appropriate?

    > >
    > >>> ---
    > >>> drivers/nfc/st-nci/se.c | 6 ++++++
    > >>> drivers/nfc/st21nfca/se.c | 6 ++++++
    > >>> net/nfc/netlink.c | 4 ++++
    > >>> 3 files changed, 16 insertions(+)
    > >>>
    > >>> diff --git a/drivers/nfc/st-nci/se.c b/drivers/nfc/st-nci/se.c
    > >>> index ec87dd21e054..b2f1ced8e6dd 100644
    > >>> --- a/drivers/nfc/st-nci/se.c
    > >>> +++ b/drivers/nfc/st-nci/se.c
    > >>> @@ -672,6 +672,12 @@ int st_nci_se_io(struct nci_dev *ndev, u32 se_idx,
    > >>> ST_NCI_EVT_TRANSMIT_DATA, apdu,
    > >>> apdu_length)
    > >> nci_hci_send_event() should also free it in its error paths.
    > >> nci_data_exchange_complete() as well? Who eventually frees it? These
    > >> might be separate patches.
    > >>
    > >>
    > >
    > > nci_hci_send_event(), as I can see, should not free the callback context.
    > > I should have probably better explained that in the commit info (will
    > > include this in the patch v2), but the main thing is: nfc_se_io() is
    > > called with se_io_cb callback function as an argument and that callback is
    > > the exact place where an allocated se_io_ctx context should be freed. And
    > > it is actually freed there unless some error path happens that leads the
    >
    > Exactly, so why nci_hci_send_event() error path should not free it?
    >

    nci_hci_send_event() should not free it on its error path because the
    bwi_timer is already charged before nci_hci_send_event() is called.

    The pattern in the .se_io functions of the corresponding drivers (st-nci,
    st21nfca) is following:

    info->se_info.cb = cb;
    info->se_info.cb_context = cb_context;
    mod_timer(&info->se_info.bwi_timer, jiffies +
    msecs_to_jiffies(info->se_info.wt_timeout)); // <-charged
    info->se_info.bwi_active = true;
    return nci_hci_send_event(...);

    As the timer is charged, it will eventually call se_io_cb() to free the
    context, even if the error path is taken inside nci_hci_send_event().

    Am I missing something?

    > > timer which triggers this se_io_cb callback not to be charged at all.
    > >
    >
    >
    > Best regards,
    > Krzysztof
    >

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