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Sun, 18 May 2025 16:15:16 +0200 Message-ID: Subject: Re: lockup and kernel panic in linux-next-202505{09,12} when compiled with clang From: Bert Karwatzki To: Jason Xing Cc: Johannes Berg , "linux-kernel@vger.kernel.org" , "linux-next@vger.kernel.org" , "llvm@lists.linux.dev" , Thomas Gleixner , linux-wireless@vger.kernel.org, spasswolf@web.de Date: Sun, 18 May 2025 16:15:15 +0200 In-Reply-To: <8274d78a82cded2fc4459fad8c2db6a1b51d7891.camel@web.de> References: <20250513164807.51780-1-spasswolf@web.de> <87h61ojg3g.ffs@tglx> <7471a185adcc34a79c2ab8ce1e87ab922ae2232b.camel@web.de> <2d8c1929bf5ab5260dacf9aa390456b3b49ce465.camel@sipsolutions.net> <2cad838b39f00d93319509d2a6a77a4c42c7fa92.camel@web.de> <8684a2b4bf367e2e2a97e2b52356ffe5436a8270.camel@sipsolutions.net> <63cc1dbf07bde2c9d14e1f86ce2c2ce26a2a9936.camel@web.de> <388bbc4c805ce029bbd08010fd30405494f998a9.camel@web.de> <15f3633cbd08b30475d5b76c5cc9180fbf17a12f.camel@web.de> <4a893f88b6892502a5f7a61bcfc806a271a730a9.camel@web.de> <8274d78a82cded2fc4459fad8c2db6a1b51d7891.camel@web.de> Content-Type: text/plain; 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> > struct sock *skc_listener; /* request_sock */ > > struct inet_timewait_death_row *skc_tw_dr; /* inet_timewait_sock */ > > }; > > @@ -221,6 +220,9 @@ struct sock_common { > > }; > > =20 > > refcount_t skc_refcnt; > > + > > + /* place skc_flags here to keep offset(struct sock, sk_refcnt) =3D= =3D 128 */ > > + unsigned long skc_flags; > > /* private: */ > > int skc_dontcopy_end[0]; > > union { > >=20 >=20 > 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: >=20 > 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_timew= ait_sock */ > }; > @@ -221,8 +220,12 @@ struct sock_common { > }; > =20 > refcount_t skc_refcnt; > + > /* private: */ > int skc_dontcopy_end[0]; > + /* place skc_flags here to keep offset(struct sock, sk_refcnt) = =3D=3D 128=20 > + * Also place it below skc_dontcopy_end[0] */ > + unsigned long skc_flags; > union { > u32 skc_rxhash; > u32 skc_window_clamp; >=20 > This locks up as usual. >=20 > Bert Karwatzki So I did some more monitoring and found that even though skc_flags is remo= ved 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 =3D ffff88fc2abf4= cc0 skb->sk->sk_flags =3D 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 =3D ffff88fbd0bd3= 210 skb->sk->sk_flags =3D 0xffffc0f1c62dcc4e [ T572] ieee80211_8023_xmit_clang_debug_helper: skb->sk =3D ffff88fbd0bd3= 210 skb->sk->sk_flags =3D 0xffffc0f1c62dcc4e Bert Karwatzki