On Wed, Jan 24, 2018 at 11:10:50AM +0100, Daniel Borkmann wrote: > On 01/24/2018 11:07 AM, David Woodhouse wrote: > > On Tue, 2018-01-09 at 22:39 +0100, Daniel Borkmann wrote: > >> On 01/09/2018 07:04 PM, Alexei Starovoitov wrote: > >>> > >>> The BPF interpreter has been used as part of the spectre 2 attack CVE-2017-5715. > >>> > >>> A quote from goolge project zero blog: > >>> "At this point, it would normally be necessary to locate gadgets in > >>> the host kernel code that can be used to actually leak data by reading > >>> from an attacker-controlled location, shifting and masking the result > >>> appropriately and then using the result of that as offset to an > >>> attacker-controlled address for a load. But piecing gadgets together > >>> and figuring out which ones work in a speculation context seems annoying. > >>> So instead, we decided to use the eBPF interpreter, which is built into > >>> the host kernel - while there is no legitimate way to invoke it from inside > >>> a VM, the presence of the code in the host kernel's text section is sufficient > >>> to make it usable for the attack, just like with ordinary ROP gadgets." > >>> > >>> To make attacker job harder introduce BPF_JIT_ALWAYS_ON config > >>> option that removes interpreter from the kernel in favor of JIT-only mode. > >>> So far eBPF JIT is supported by: > >>> x64, arm64, arm32, sparc64, s390, powerpc64, mips64 > >>> > >>> The start of JITed program is randomized and code page is marked as read-only. > >>> In addition "constant blinding" can be turned on with net.core.bpf_jit_harden > >>> > >>> v2->v3: > >>> - move __bpf_prog_ret0 under ifdef (Daniel) > >>> > >>> v1->v2: > >>> - fix init order, test_bpf and cBPF (Daniel's feedback) > >>> - fix offloaded bpf (Jakub's feedback) > >>> - add 'return 0' dummy in case something can invoke prog->bpf_func > >>> - retarget bpf tree. For bpf-next the patch would need one extra hunk. > >>> It will be sent when the trees are merged back to net-next > >>> > >>> Considered doing: > >>> int bpf_jit_enable __read_mostly = BPF_EBPF_JIT_DEFAULT; > >>> but it seems better to land the patch as-is and in bpf-next remove > >>> bpf_jit_enable global variable from all JITs, consolidate in one place > >>> and remove this jit_init() function. > >>> > >>> Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx> > >> > >> Applied to bpf tree, thanks Alexei! > > > > For stable too? > > Yes, this will go into stable as well; batch of backports will come Thurs/Fri. Any word on these? Worse case, a simple list of git commit ids to backport is all I need. thanks, greg k-h