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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: Clear (ClamAV 1.4.3/28119/Thu Sep 10 08:24:09 2026) On 9/10/26 5:41 PM, Alexei Starovoitov wrote: > On Thu Sep 10, 2026 at 7:21 AM PDT, Daniel Borkmann wrote: >> Mark fault-safe probe reading kfuncs as KF_PERFMON, similarly as we do for >> the old-style BPF helper equivalents. bpf_rdonly_cast() is included in this >> list as well as it returns PTR_TO_MEM | MEM_RDONLY | PTR_UNTRUSTED for an >> unchecked object and is using fault-safe BPF_PROBE_MEM. >> >> Note that only the void form of bpf_rdonly_cast() produced a register that >> was readable without CAP_PERFMON. For a struct type id the kfunc returns >> PTR_TO_BTF_ID | PTR_UNTRUSTED, whose dereference has always been gated in >> check_ptr_to_btf_access(). The flag is not conditional on the type id, so >> for the latter it only moves the rejection from the dereference to the call >> itself, which is the better place to report it anyway. >> >> The bpf_stream_vprintk() and bpf_stream_print_stack() kfuncs are marked >> as well. The former ends up in the same bpf_bprintf_prepare() as the >> bpf_snprintf() helper, where %pks, %pus and %pI4 read through a program- >> supplied address and %pB resolves one into a symbol. The latter walks the >> stack and prints each instruction pointer via %pS. >> >> Fixes: 4665415975b0 ("bpf: Add bits iterator") >> Fixes: 65ab5ac4df01 ("bpf: Add bpf_copy_from_user_str kfunc") >> Fixes: f0f8a5b58f78 ("bpf: Add bpf_copy_from_user_task_str() kfunc") >> Fixes: a498ee7576de ("bpf: Implement dynptr copy kfuncs") >> Fixes: f2362a57aeff ("bpf: allow void* cast using bpf_rdonly_cast()") >> Fixes: e91370550f1f ("bpf: Add kfuncs for read-only string operations") >> Fixes: 5ab154f1463a ("bpf: Introduce BPF standard streams") >> Fixes: 19559e844184 ("bpf: add bpf_strcasecmp kfunc") >> Fixes: b5b693f73589 ("bpf: add bpf_strcasestr,bpf_strncasestr kfuncs") >> Fixes: 1dc669646762 ("bpf: add bpf_strncasecmp kfunc") >> Fixes: 63328bb23f26 ("bpf: Add bpf_stream_print_stack stack dumping kfunc") > > Let's drop this Fixes list altogether, since it will only cause > headaches to stable folks. We don't need to backport this everywhere. > Not really an issue. > CAP_BPF alone can leak memory via HW speculation, > so this patch isn't strictly necessary, but I don't mind closing the hole > since AI keeps reporting it. > > Also pls add bpf_get_kmem_cache() as AI suggested. Ack, will address and also the one from your other email. Thanks, Daniel