commit 212253367dc7b49ed3fc194ce71b0992eacaecf2
author Paulo Alcantara <pc@cjr.nz> Sat Nov 28 16:54:02 2020 -0300
committer Steve French <stfrench@microsoft.com> Mon Nov 30 15:23:45 2020 -0600
tree f70fc65d0b8eda01cf1c7d37b2bf212840cd4096
parent 6988a619f5b79e4efadea6e19dcfe75fbcd350b5

cifs: fix potential use-after-free in cifs_echo_request()

This patch fixes a potential use-after-free bug in
cifs_echo_request().

For instance,

  thread 1
  --------
  cifs_demultiplex_thread()
    clean_demultiplex_info()
      kfree(server)

  thread 2 (workqueue)
  --------
  apic_timer_interrupt()
    smp_apic_timer_interrupt()
      irq_exit()
        __do_softirq()
          run_timer_softirq()
            call_timer_fn()
	      cifs_echo_request() <- use-after-free in server ptr

Signed-off-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
CC: Stable <stable@vger.kernel.org>
Reviewed-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>