netdev - Re: [PATCH V2] Fix a sleep-in-atomic bug in shash_setkey

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Message-ID: <20171003223308.GD19750@localhost.localdomain>
Date:   Tue, 3 Oct 2017 19:33:08 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Jia-Ju Bai <baijiaju1990@....com>
Cc:     davem@...emloft.net, herbert@...dor.apana.org.au,
        nhorman@...driver.com, vyasevich@...il.com, luto@...nel.org,
        kvalo@...eaurora.org, linux-crypto@...r.kernel.org,
        netdev@...r.kernel.org, linux-sctp@...r.kernel.org,
        linux-wireless@...r.kernel.org
Subject: Re: [PATCH V2] Fix a sleep-in-atomic bug in shash_setkey_unaligned

On Tue, Oct 03, 2017 at 10:25:22AM +0800, Jia-Ju Bai wrote:
> The SCTP program may sleep under a spinlock, and the function call path is:
> sctp_generate_t3_rtx_event (acquire the spinlock)
>   sctp_do_sm
>     sctp_side_effects
>       sctp_cmd_interpreter
>         sctp_make_init_ack
>           sctp_pack_cookie
>             crypto_shash_setkey
>               shash_setkey_unaligned
>                 kmalloc(GFP_KERNEL)

Are you sure this can happen?
The host is not supposed to store any information when replying to an
INIT packet (which generated the INIT_ACK listed above). That said,
it's weird to see the timer function triggering so.

Checking now, that code is dead actually:
$ git grep -A 2 SCTP_CMD_GEN_INIT_ACK
sm_sideeffect.c:                case SCTP_CMD_GEN_INIT_ACK:
sm_sideeffect.c-                        /* Generate an INIT ACK chunk.
*/
sm_sideeffect.c-                        new_obj =
sctp_make_init_ack(asoc, chunk, GFP_ATOMIC,

Nobody is triggering a call to sctp_cmd_interpreter with
SCTP_CMD_GEN_INIT_ACK command, which would generate the callstack
above.

  Marcelo