>On 4/18/22 18:49, Chuck Lever wrote: >> The sk_psock facility populates the sk_user_data field with the >> address of an extra bit of metadata. User space sockets never >> populate the sk_user_data field, so this has worked out fine. >> >> However, kernel consumers such as the RPC client and server do >> populate the sk_user_data field. The sk_psock() function cannot tell >> that the content of sk_user_data does not point to psock metadata, >> so it will happily return a pointer to something else, cast to a >> struct sk_psock. >> >> Thus kernel consumers and psock currently cannot co-exist. >> >> We could educate sk_psock() to return NULL if sk_user_data does >> not point to a struct sk_psock. However, a more general solution >> that enables full co-existence psock and other uses of sk_user_data >> might be more interesting. >> >> Move the struct sk_psock address to its own pointer field so that >> the contents of the sk_user_data field is preserved. >> >> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx> >> --- >> include/linux/skmsg.h | 2 +- >> include/net/sock.h | 4 +++- >> net/core/skmsg.c | 6 +++--- >> 3 files changed, 7 insertions(+), 5 deletions(-) >> >Reviewed-by: Hannes Reinecke <hare@xxxxxxx> > >Cheers, > >Hannes In Patchwork website, this patch fails the checks on netdev/cc_maintainers. So maybe you need CC folks pointed out by scripts/get_maintainer.pl script, which is suggested by Jakub Kicinski <kuba@xxxxxxxxxx>. What's more, Syskaller reports refcount bug in sk_psock_get (2). In this bug, the problem is that smc and psock, both use sk_user_data field to save their private data. So they will treat field in their own way. > in smc_switch_to_fallback(), and set smc->clcsock->sk_user_data > to origin smc in smc_fback_replace_callbacks(). > > Later, sk_psock_get() will treat the smc->clcsock->sk_user_data > as sk_psock type, which triggers the refcnt warning. I have tested this patch and the reproducer did not trigger any issue. For more details, you can check the email [PATCH] smc: fix refcount bug in sk_psock_get (2)
