netdev - [BUG] net: smc: possible deadlock in smc_lgr_free() and smc_link_down

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 1 Feb 2022 15:51:30 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     kgraul@...ux.ibm.com, davem@...emloft.net, kuba@...nel.org
Cc:     linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: [BUG] net: smc: possible deadlock in smc_lgr_free() and
 smc_link_down_work()

Hello,

My static analysis tool reports a possible deadlock in the smc module in 
Linux 5.16:

smc_lgr_free()
   mutex_lock(&lgr->llc_conf_mutex); --> Line 1289 (Lock A)
   smcr_link_clear()
     smc_wr_free_link()
       wait_event(lnk->wr_tx_wait, ...); --> Line 648 (Wait X)

smc_link_down_work()
   mutex_lock(&lgr->llc_conf_mutex); --> Line 1683 (Lock A)
   smcr_link_down()
     smcr_link_clear()
       smc_wr_free_link()
         smc_wr_wakeup_tx_wait()
           wake_up_all(&lnk->wr_tx_wait); --> Line 78 (Wake X)

When smc_lgr_free() is executed, "Wait X" is performed by holding "Lock 
A". If smc_link_down_work() is executed at this time, "Wake X" cannot be 
performed to wake up "Wait X" in smc_lgr_free(), because "Lock A" has 
been already hold by smc_lgr_free(), causing a possible deadlock.

I am not quite sure whether this possible problem is real and how to fix 
it if it is real.
Any feedback would be appreciated, thanks :)

Best wishes,
Jia-Ju Bai