Am Sonntag, dem 18.05.2025 um 16:15 +0200 schrieb Bert Karwatzki:
> Am Sonntag, dem 18.05.2025 um 14:43 +0200 schrieb Bert Karwatzki:
> > Am Sonntag, dem 18.05.2025 um 14:12 +0200 schrieb Bert Karwatzki:
> > > > > >
> > >
> > > I even tried this version of your patch, to keep the offset of skc_refcnt at 128,
> > > but it doesn't work, either.
> > >
> > > commit fca84c5cde713be480544a64ed6680afc3319670
> > > Author: Bert Karwatzki <spasswolf@xxxxxx>
> > > Date: Sun May 18 13:32:36 2025 +0200
> > >
> > > include: net: sock: move skc_flags out of the union
> > >
> > > Signed-off-by: Bert Karwatzki <spasswolf@xxxxxx>
> > >
> > > diff --git a/include/net/sock.h b/include/net/sock.h
> > > index 3e15d7105ad2..e73929a4da6e 100644
> > > --- a/include/net/sock.h
> > > +++ b/include/net/sock.h
> > > @@ -195,7 +195,6 @@ struct sock_common {
> > > * for different kind of 'sockets'
> > > */
> > > union {
> > > - unsigned long skc_flags;
> > > struct sock *skc_listener; /* request_sock */
> > > struct inet_timewait_death_row *skc_tw_dr; /* inet_timewait_sock */
> > > };
> > > @@ -221,6 +220,9 @@ struct sock_common {
> > > };
> > >
> > > refcount_t skc_refcnt;
> > > +
> > > + /* place skc_flags here to keep offset(struct sock, sk_refcnt) == 128 */
> > > + unsigned long skc_flags;
> > > /* private: */
> > > int skc_dontcopy_end[0];
> > > union {
> > >
> >
> > In the patch above I accidently put skc_flags in the part of struct sock_common
> > which does not get copied, but putting it below skc_dontcopy_end[0] does not work,
> > either:
> >
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 3e15d7105ad2..6d69753a205a 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -195,7 +195,6 @@ struct sock_common {
> > * for different kind of 'sockets'
> > */
> > union {
> > - unsigned long skc_flags;
> > struct sock *skc_listener; /* request_sock */
> > struct inet_timewait_death_row *skc_tw_dr; /* inet_timewait_sock */
> > };
> > @@ -221,8 +220,12 @@ struct sock_common {
> > };
> >
> > refcount_t skc_refcnt;
> > +
> > /* private: */
> > int skc_dontcopy_end[0];
> > + /* place skc_flags here to keep offset(struct sock, sk_refcnt) == 128
> > + * Also place it below skc_dontcopy_end[0] */
> > + unsigned long skc_flags;
> > union {
> > u32 skc_rxhash;
> > u32 skc_window_clamp;
> >
> > This locks up as usual.
> >
> > Bert Karwatzki
>
> So I did some more monitoring and found that even though skc_flags is removed from the union
> it can take strange values, e.g.:
>
> Here the value is not even a pointer (perhaps unitialized memory?):
> [ T572] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff88fc2abf4cc0 skb->sk->sk_flags = 0xa00f7fe57b16f7e1
> These could be pointers, but as pointers would only be aligned to a 2-byte boundary ...
> [ T572] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff88fbd0bd3210 skb->sk->sk_flags = 0xffffc0f1c62dcc4e
> [ T572] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff88fbd0bd3210 skb->sk->sk_flags = 0xffffc0f1c62dcc4e
>
> Bert Karwatzki
I tried to set sk_flags to 0 in sk_prot_alloc() like this:
commit 269f21266477e74321e32e0b022dda8e98785589 (HEAD -> clang_panic)
Author: Bert Karwatzki <spasswolf@xxxxxx>
Date: Sun May 18 16:28:39 2025 +0200
net: core: sock: set initial sk_flags to 0 in sk_prot_alloc()
Signed-off-by: Bert Karwatzki <spasswolf@xxxxxx>
diff --git a/net/core/sock.c b/net/core/sock.c
index f6589ad5ba36..acaa39ad18be 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2216,6 +2216,7 @@ static struct sock *sk_prot_alloc(struct proto *prot, gfp_t priority,
goto out_free_sec;
}
+ sk->sk_flags = 0;
return sk;
out_free_sec:
But that didn't work:
[ 13.832282] [ T579] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff8962805faee0 skb->sk->sk_flags = 0x4472000044f00000
[...]
[ 124.165094] [ T579] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff896280760550 skb->sk->sk_flags = 0x726f2e65746f7571
[...]
[ 185.138202] [ T579] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff8960c78b7a90 skb->sk->sk_flags = 0x8000000000000025
[...]
[ 290.623998] [ T579] ieee80211_8023_xmit_clang_debug_helper: skb->sk = ffff8961936b7870 skb->sk->sk_flags = 0xffff8961936b78f0
Bert Karwatzki
