net/smc: Avoid overwriting the copies of clcsock callback functions

mainline inclusion
from mainline-v5.17-rc5
commit 1de9770d
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I76JHC
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/net/smc?id=1de9770d121ee9294794cca0e0be8fbfa0134ee8



--------------------------------

The callback functions of clcsock will be saved and replaced during
the fallback. But if the fallback happens more than once, then the
copies of these callback functions will be overwritten incorrectly,
resulting in a loop call issue:

clcsk->sk_error_report
 |- smc_fback_error_report() <------------------------------|
     |- smc_fback_forward_wakeup()                          | (loop)
         |- clcsock_callback()  (incorrectly overwritten)   |
             |- smc->clcsk_error_report() ------------------|

So this patch fixes the issue by saving these function pointers only
once in the fallback and avoiding overwriting.

Reported-by:  <syzbot+4de3c0e8a263e1e499bc@syzkaller.appspotmail.com>
Fixes: 341adeec ("net/smc: Forward wakeup to smc socket waitqueue after fallback")
Link: https://lore.kernel.org/r/0000000000006d045e05d78776f6@google.com


Signed-off-by: Wen Gu <guwen@linux.alibaba.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Litao Jiao <jiaolitao@sangfor.com.cn>