From mboxrd@z Thu Jan 1 00:00:00 1970 From: alexei.starovoitov@gmail.com (Alexei Starovoitov) Date: Thu, 19 Oct 2017 16:31:08 -0700 Subject: [PATCH 18/27] bpf: Restrict kernel image access functions when the kernel is locked down In-Reply-To: <482.1508453314@warthog.procyon.org.uk> References: <20171019221829.7m5nczg3ltqmhzom@ast-mbp> <150842463163.7923.11081723749106843698.stgit@warthog.procyon.org.uk> <150842476953.7923.18174368926573855810.stgit@warthog.procyon.org.uk> <482.1508453314@warthog.procyon.org.uk> Message-ID: <20171019233105.5ladqpdf2me36j7q@ast-mbp> To: linux-security-module@vger.kernel.org List-Id: linux-security-module.vger.kernel.org On Thu, Oct 19, 2017 at 11:48:34PM +0100, David Howells wrote: > Alexei Starovoitov wrote: > > > > @@ -65,6 +65,11 @@ BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) > > > { > > > int ret; > > > > > > + if (kernel_is_locked_down("BPF")) { > > > + memset(dst, 0, size); > > > + return -EPERM; > > > + } > > > > That doesn't help the lockdown purpose. > > If you don't trust the root the only way to prevent bpf read > > memory is to disable the whole thing. > > Have a single check in sys_bpf() to disallow everything if kernel_is_locked_down() > > and don't add overhead to critical path like bpf_probe_read(). > > TBH, I've no idea how bpf does anything, so I can't say whether this is > better, overkill or insufficient. ok. To make it clear: Nacked-by: Alexei Starovoitov For the current patch. Unnecessary checks for no good reason in performance critical functions are not acceptable. -- To unsubscribe from this list: send the line "unsubscribe linux-security-module" in the body of a message to majordomo at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html