Messages in this thread |  | | Date | Thu, 9 Apr 2026 19:58:40 -0500 | | From | "Serge E. Hallyn" <> | | Subject | Re: [PATCH] security: remove BUG_ON in security_skb_classify_flow |
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On Wed, Apr 08, 2026 at 07:42:57PM +0800, Jiayuan Chen wrote: > A BPF program attached to the xfrm_decode_session hook can return a > non-zero value, which causes BUG_ON(rc) in security_skb_classify_flow() > to trigger a kernel panic.
It would seem worth it to have pointed at the previous discussion at
https://lore.kernel.org/all/CAEjxPJ5aA01in+Z1yLF1cwe-3uqL_E8SKGK4J294D5eRG5__5Q@mail.gmail.com/
Based on that, I guess this is probably ok, but still,
> Remove the BUG_ON and change the return type from void to int, so that > callers can optionally handle the error.
but you don't have the existing callers handling the error. It's conceivable they won't care, but it's also possible that they were counting on a BUG_ON in that case.
What *should* callers (icmp_reply, etc) do if an error code is returned? Should they ignore it? In that case, would it be better to change security_skb_classify_flow() to return void?
> Reported-by: Kaiyan Mei <M202472210@hust.edu.cn> > Reported-by: Yinhao Hu <dddddd@hust.edu.cn> > Reported-by: Dongliang Mu <dzm91@hust.edu.cn> > Closes: https://lore.kernel.org/bpf/4c4d04ba.6c12b.19c039b69e6.Coremail.kaiyanm@hust.edu.cn/ > Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev> > --- > include/linux/security.h | 7 ++++--- > security/security.c | 16 +++++++++++----- > 2 files changed, 15 insertions(+), 8 deletions(-) > > diff --git a/include/linux/security.h b/include/linux/security.h > index ee88dd2d2d1f..6d210dc4c649 100644 > --- a/include/linux/security.h > +++ b/include/linux/security.h > @@ -1975,7 +1975,7 @@ int security_xfrm_state_pol_flow_match(struct xfrm_state *x, > struct xfrm_policy *xp, > const struct flowi_common *flic); > int security_xfrm_decode_session(struct sk_buff *skb, u32 *secid); > -void security_skb_classify_flow(struct sk_buff *skb, struct flowi_common *flic); > +int security_skb_classify_flow(struct sk_buff *skb, struct flowi_common *flic); > > #else /* CONFIG_SECURITY_NETWORK_XFRM */ > > @@ -2038,9 +2038,10 @@ static inline int security_xfrm_decode_session(struct sk_buff *skb, u32 *secid) > return 0; > } > > -static inline void security_skb_classify_flow(struct sk_buff *skb, > - struct flowi_common *flic) > +static inline int security_skb_classify_flow(struct sk_buff *skb, > + struct flowi_common *flic) > { > + return 0; > } > > #endif /* CONFIG_SECURITY_NETWORK_XFRM */ > diff --git a/security/security.c b/security/security.c > index a26c1474e2e4..26a34eb363c2 100644 > --- a/security/security.c > +++ b/security/security.c > @@ -4990,12 +4990,18 @@ int security_xfrm_decode_session(struct sk_buff *skb, u32 *secid) > return call_int_hook(xfrm_decode_session, skb, secid, 1); > } > > -void security_skb_classify_flow(struct sk_buff *skb, struct flowi_common *flic) > +/** > + * security_skb_classify_flow() - Set the flow's secid from the security label > + * @skb: packet > + * @flic: flow common structure to set > + * > + * Decode the packet in @skb and set the flow's secid in @flic. > + * > + * Return: Return 0 if successful. > + */ > +int security_skb_classify_flow(struct sk_buff *skb, struct flowi_common *flic) > { > - int rc = call_int_hook(xfrm_decode_session, skb, &flic->flowic_secid, > - 0); > - > - BUG_ON(rc); > + return call_int_hook(xfrm_decode_session, skb, &flic->flowic_secid, 0); > } > EXPORT_SYMBOL(security_skb_classify_flow); > #endif /* CONFIG_SECURITY_NETWORK_XFRM */ > -- > 2.43.0
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