kernel/linux.git/include/linux/filter.h, branch v4.18.11

xdp: XDP_REDIRECT should check IFF_UP and MTU

2018-07-07T22:25:35+00:00

Otherwise we end up with attempting to send packets from down devices or to send oversized packets, which may cause unexpected driver/device behaviour. Generic XDP has already done this check, so reuse the logic in native XDP. Fixes: 814abfabef3c ("xdp: add bpf_redirect helper function") Signed-off-by: Toshiaki Makita Signed-off-by: Alexei Starovoitov

bpf: undo prog rejection on read-only lock failure

2018-06-29T17:47:35+00:00

Partially undo commit 9facc336876f ("bpf: reject any prog that failed read-only lock") since it caused a regression, that is, syzkaller was able to manage to cause a panic via fault injection deep in set_memory_ro() path by letting an allocation fail: In x86's __change_page_attr_set_clr() it was able to change the attributes of the primary mapping but not in the alias mapping via cpa_process_alias(), so the second, inner call to the __change_page_attr() via __change_page_attr_set_clr() had to split a larger page and failed in the alloc_pages() with the artifically triggered allocation error which is then propagated down to the call site. Thus, for set_memory_ro() this means that it returned with an error, but from debugging a probe_kernel_write() revealed EFAULT on that memory since the primary mapping succeeded to get changed. Therefore the subsequent hdr->locked = 0 reset triggered the panic as it was performed on read-only memory, so call-site assumptions were infact wrong to assume that it would either succeed /or/ not succeed at all since there's no such rollback in set_memory_*() calls from partial change of mappings, in other words, we're left in a state that is "half done". A later undo via set_memory_rw() is succeeding though due to matching permissions on that part (aka due to the try_preserve_large_page() succeeding). While reproducing locally with explicitly triggering this error, the initial splitting only happens on rare occasions and in real world it would additionally need oom conditions, but that said, it could partially fail. Therefore, it is definitely wrong to bail out on set_memory_ro() error and reject the program with the set_memory_*() semantics we have today. Shouldn't have gone the extra mile since no other user in tree today infact checks for any set_memory_*() errors, e.g. neither module_enable_ro() / module_disable_ro() for module RO/NX handling which is mostly default these days nor kprobes core with alloc_insn_page() / free_insn_page() as examples that could be invoked long after bootup and original 314beb9bcabf ("x86: bpf_jit_comp: secure bpf jit against spraying attacks") did neither when it got first introduced to BPF so "improving" with bailing out was clearly not right when set_memory_*() cannot handle it today. Kees suggested that if set_memory_*() can fail, we should annotate it with __must_check, and all callers need to deal with it gracefully given those set_memory_*() markings aren't "advisory", but they're expected to actually do what they say. This might be an option worth to move forward in future but would at the same time require that set_memory_*() calls from supporting archs are guaranteed to be "atomic" in that they provide rollback if part of the range fails, once that happened, the transition from RW -> RO could be made more robust that way, while subsequent RO -> RW transition /must/ continue guaranteeing to always succeed the undo part. Reported-by: syzbot+a4eb8c7766952a1ca872@syzkaller.appspotmail.com Reported-by: syzbot+d866d1925855328eac3b@syzkaller.appspotmail.com Fixes: 9facc336876f ("bpf: reject any prog that failed read-only lock") Cc: Laura Abbott Cc: Kees Cook Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Signed-off-by: Alexei Starovoitov

bpf: enforce correct alignment for instructions

2018-06-21T03:46:06+00:00

After commit 9facc336876f ("bpf: reject any prog that failed read-only lock") offsetof(struct bpf_binary_header, image) became 3 instead of 4, breaking powerpc BPF badly, since instructions need to be word aligned. Fixes: 9facc336876f ("bpf: reject any prog that failed read-only lock") Signed-off-by: Eric Dumazet Cc: Daniel Borkmann Cc: Martin KaFai Lau Cc: Alexei Starovoitov Signed-off-by: David S. Miller

xdp: Fix handling of devmap in generic XDP

2018-06-15T21:47:15+00:00

Commit 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") changed the return value type of __devmap_lookup_elem() from struct net_device * to struct bpf_dtab_netdev * but forgot to modify generic XDP code accordingly. Thus generic XDP incorrectly used struct bpf_dtab_netdev where struct net_device is expected, then skb->dev was set to invalid value. v2: - Fix compiler warning without CONFIG_BPF_SYSCALL. Fixes: 67f29e07e131 ("bpf: devmap introduce dev_map_enqueue") Signed-off-by: Toshiaki Makita Acked-by: Yonghong Song Acked-by: Jesper Dangaard Brouer Signed-off-by: Daniel Borkmann

bpf: reject any prog that failed read-only lock

2018-06-15T18:14:25+00:00

We currently lock any JITed image as read-only via bpf_jit_binary_lock_ro() as well as the BPF image as read-only through bpf_prog_lock_ro(). In the case any of these would fail we throw a WARN_ON_ONCE() in order to yell loudly to the log. Perhaps, to some extend, this may be comparable to an allocation where __GFP_NOWARN is explicitly not set. Added via 65869a47f348 ("bpf: improve read-only handling"), this behavior is slightly different compared to any of the other in-kernel set_memory_ro() users who do not check the return code of set_memory_ro() and friends /at all/ (e.g. in the case of module_enable_ro() / module_disable_ro()). Given in BPF this is mandatory hardening step, we want to know whether there are any issues that would leave both BPF data writable. So it happens that syzkaller enabled fault injection and it triggered memory allocation failure deep inside x86's change_page_attr_set_clr() which was triggered from set_memory_ro(). Now, there are two options: i) leaving everything as is, and ii) reworking the image locking code in order to have a final checkpoint out of the central bpf_prog_select_runtime() which probes whether any of the calls during prog setup weren't successful, and then bailing out with an error. Option ii) is a better approach since this additional paranoia avoids altogether leaving any potential W+X pages from BPF side in the system. Therefore, lets be strict about it, and reject programs in such unlikely occasion. While testing I noticed also that one bpf_prog_lock_ro() call was missing on the outer dummy prog in case of calls, e.g. in the destructor we call bpf_prog_free_deferred() on the main prog where we try to bpf_prog_unlock_free() the program, and since we go via bpf_prog_select_runtime() do that as well. Reported-by: syzbot+3b889862e65a98317058@syzkaller.appspotmail.com Reported-by: syzbot+9e762b52dd17e616a7a5@syzkaller.appspotmail.com Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov

bpf: fix panic in prog load calls cleanup

2018-06-15T18:14:25+00:00

While testing I found that when hitting error path in bpf_prog_load() where we jump to free_used_maps and prog contained BPF to BPF calls that were JITed earlier, then we never clean up the bpf_prog_kallsyms_add() done under jit_subprogs(). Add proper API to make BPF kallsyms deletion more clear and fix that. Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs") Signed-off-by: Daniel Borkmann Acked-by: Martin KaFai Lau Signed-off-by: Alexei Starovoitov

bpf: fix context access in tracing progs on 32 bit archs

2018-06-03T14:46:56+00:00

Wang reported that all the testcases for BPF_PROG_TYPE_PERF_EVENT program type in test_verifier report the following errors on x86_32: 172/p unpriv: spill/fill of different pointers ldx FAIL Unexpected error message! 0: (bf) r6 = r10 1: (07) r6 += -8 2: (15) if r1 == 0x0 goto pc+3 R1=ctx(id=0,off=0,imm=0) R6=fp-8,call_-1 R10=fp0,call_-1 3: (bf) r2 = r10 4: (07) r2 += -76 5: (7b) *(u64 *)(r6 +0) = r2 6: (55) if r1 != 0x0 goto pc+1 R1=ctx(id=0,off=0,imm=0) R2=fp-76,call_-1 R6=fp-8,call_-1 R10=fp0,call_-1 fp-8=fp 7: (7b) *(u64 *)(r6 +0) = r1 8: (79) r1 = *(u64 *)(r6 +0) 9: (79) r1 = *(u64 *)(r1 +68) invalid bpf_context access off=68 size=8 378/p check bpf_perf_event_data->sample_period byte load permitted FAIL Failed to load prog 'Permission denied'! 0: (b7) r0 = 0 1: (71) r0 = *(u8 *)(r1 +68) invalid bpf_context access off=68 size=1 379/p check bpf_perf_event_data->sample_period half load permitted FAIL Failed to load prog 'Permission denied'! 0: (b7) r0 = 0 1: (69) r0 = *(u16 *)(r1 +68) invalid bpf_context access off=68 size=2 380/p check bpf_perf_event_data->sample_period word load permitted FAIL Failed to load prog 'Permission denied'! 0: (b7) r0 = 0 1: (61) r0 = *(u32 *)(r1 +68) invalid bpf_context access off=68 size=4 381/p check bpf_perf_event_data->sample_period dword load permitted FAIL Failed to load prog 'Permission denied'! 0: (b7) r0 = 0 1: (79) r0 = *(u64 *)(r1 +68) invalid bpf_context access off=68 size=8 Reason is that struct pt_regs on x86_32 doesn't fully align to 8 byte boundary due to its size of 68 bytes. Therefore, bpf_ctx_narrow_access_ok() will then bail out saying that off & (size_default - 1) which is 68 & 7 doesn't cleanly align in the case of sample_period access from struct bpf_perf_event_data, hence verifier wrongly thinks we might be doing an unaligned access here though underlying arch can handle it just fine. Therefore adjust this down to machine size and check and rewrite the offset for narrow access on that basis. We also need to fix corresponding pe_prog_is_valid_access(), since we hit the check for off % size != 0 (e.g. 68 % 8 -> 4) in the first and last test. With that in place, progs for tracing work on x86_32. Reported-by: Wang YanQing Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Tested-by: Wang YanQing Signed-off-by: Alexei Starovoitov

bpf: avoid retpoline for lookup/update/delete calls on maps

2018-06-03T14:45:37+00:00

While some of the BPF map lookup helpers provide a ->map_gen_lookup() callback for inlining the map lookup altogether it is not available for every map, so the remaining ones have to call bpf_map_lookup_elem() helper which does a dispatch to map->ops->map_lookup_elem(). In times of retpolines, this will control and trap speculative execution rather than letting it do its work for the indirect call and will therefore cause a slowdown. Likewise, bpf_map_update_elem() and bpf_map_delete_elem() do not have an inlined version and need to call into their map->ops->map_update_elem() resp. map->ops->map_delete_elem() handlers. Before: # bpftool prog dump xlated id 1 0: (bf) r2 = r10 1: (07) r2 += -8 2: (7a) *(u64 *)(r2 +0) = 0 3: (18) r1 = map[id:1] 5: (85) call __htab_map_lookup_elem#232656 6: (15) if r0 == 0x0 goto pc+4 7: (71) r1 = *(u8 *)(r0 +35) 8: (55) if r1 != 0x0 goto pc+1 9: (72) *(u8 *)(r0 +35) = 1 10: (07) r0 += 56 11: (15) if r0 == 0x0 goto pc+4 12: (bf) r2 = r0 13: (18) r1 = map[id:1] 15: (85) call bpf_map_delete_elem#215008 <-- indirect call via 16: (95) exit helper After: # bpftool prog dump xlated id 1 0: (bf) r2 = r10 1: (07) r2 += -8 2: (7a) *(u64 *)(r2 +0) = 0 3: (18) r1 = map[id:1] 5: (85) call __htab_map_lookup_elem#233328 6: (15) if r0 == 0x0 goto pc+4 7: (71) r1 = *(u8 *)(r0 +35) 8: (55) if r1 != 0x0 goto pc+1 9: (72) *(u8 *)(r0 +35) = 1 10: (07) r0 += 56 11: (15) if r0 == 0x0 goto pc+4 12: (bf) r2 = r0 13: (18) r1 = map[id:1] 15: (85) call htab_lru_map_delete_elem#238240 <-- direct call 16: (95) exit In all three lookup/update/delete cases however we can use the actual address of the map callback directly if we find that there's only a single path with a map pointer leading to the helper call, meaning when the map pointer has not been poisoned from verifier side. Example code can be seen above for the delete case. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Acked-by: Song Liu Signed-off-by: Alexei Starovoitov

bpf: test case for map pointer poison with calls/branches

2018-06-03T14:42:06+00:00

Add several test cases where the same or different map pointers originate from different paths in the program and execute a map lookup or tail call at a common location. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov Acked-by: Song Liu Signed-off-by: Alexei Starovoitov

bpf: Hooks for sys_sendmsg

2018-05-28T15:41:02+00:00

In addition to already existing BPF hooks for sys_bind and sys_connect, the patch provides new hooks for sys_sendmsg. It leverages existing BPF program type `BPF_PROG_TYPE_CGROUP_SOCK_ADDR` that provides access to socket itlself (properties like family, type, protocol) and user-passed `struct sockaddr *` so that BPF program can override destination IP and port for system calls such as sendto(2) or sendmsg(2) and/or assign source IP to the socket. The hooks are implemented as two new attach types: `BPF_CGROUP_UDP4_SENDMSG` and `BPF_CGROUP_UDP6_SENDMSG` for UDPv4 and UDPv6 correspondingly. UDPv4 and UDPv6 separate attach types for same reason as sys_bind and sys_connect hooks, i.e. to prevent reading from / writing to e.g. user_ip6 fields when user passes sockaddr_in since it'd be out-of-bound. The difference with already existing hooks is sys_sendmsg are implemented only for unconnected UDP. For TCP it doesn't make sense to change user-provided `struct sockaddr *` at sendto(2)/sendmsg(2) time since socket either was already connected and has source/destination set or wasn't connected and call to sendto(2)/sendmsg(2) would lead to ENOTCONN anyway. Connected UDP is already handled by sys_connect hooks that can override source/destination at connect time and use fast-path later, i.e. these hooks don't affect UDP fast-path. Rewriting source IP is implemented differently than that in sys_connect hooks. When sys_sendmsg is used with unconnected UDP it doesn't work to just bind socket to desired local IP address since source IP can be set on per-packet basis by using ancillary data (cmsg(3)). So no matter if socket is bound or not, source IP has to be rewritten on every call to sys_sendmsg. To do so two new fields are added to UAPI `struct bpf_sock_addr`; * `msg_src_ip4` to set source IPv4 for UDPv4; * `msg_src_ip6` to set source IPv6 for UDPv6. Signed-off-by: Andrey Ignatov Acked-by: Alexei Starovoitov Acked-by: Martin KaFai Lau Signed-off-by: Daniel Borkmann