| Message ID | 20180621002409.63136-1-edumazet@google.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
| Series | [net] bpf: enforce correct alignment for instructions | expand |
From: Eric Dumazet <edumazet@google.com> Date: Wed, 20 Jun 2018 17:24:09 -0700 > 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 <edumazet@google.com> I'll apply this directly, thanks Eric.
On 06/20/2018 08:46 PM, David Miller wrote: > From: Eric Dumazet <edumazet@google.com> > Date: Wed, 20 Jun 2018 17:24:09 -0700 > >> 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 <edumazet@google.com> > > I'll apply this directly, thanks Eric. > Thanks David :)
On 06/21/2018 06:08 AM, Eric Dumazet wrote: > On 06/20/2018 08:46 PM, David Miller wrote: >> From: Eric Dumazet <edumazet@google.com> >> Date: Wed, 20 Jun 2018 17:24:09 -0700 >> >>> 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 <edumazet@google.com> >> >> I'll apply this directly, thanks Eric. > > Thanks David :) Sigh, sorry for the breakage, looks like I got fooled by x86 gcc. struct bpf_binary_header { u16 pages; /* 0 2 */ u16 locked:1; /* 2:15 2 */ /* XXX 15 bits hole, try to pack */ u8 image[0]; /* 4 0 */ /* size: 4, cachelines: 1, members: 3 */ /* bit holes: 1, sum bit holes: 15 bits */ /* last cacheline: 4 bytes */ }; Thanks Eric!
From: Daniel Borkmann <daniel@iogearbox.net> Date: Thu, 21 Jun 2018 23:03:09 +0200 > On 06/21/2018 06:08 AM, Eric Dumazet wrote: >> On 06/20/2018 08:46 PM, David Miller wrote: >>> From: Eric Dumazet <edumazet@google.com> >>> Date: Wed, 20 Jun 2018 17:24:09 -0700 >>> >>>> 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 <edumazet@google.com> >>> >>> I'll apply this directly, thanks Eric. >> >> Thanks David :) > > Sigh, sorry for the breakage, looks like I got fooled by x86 gcc. > > struct bpf_binary_header { > u16 pages; /* 0 2 */ > u16 locked:1; /* 2:15 2 */ Note that you can also just make locked a plan u16 for now until you need more flag bits, the code generated will be more efficient especially on non-x86.
diff --git a/include/linux/filter.h b/include/linux/filter.h index b615df57b7d5b2ccb468c411c3a2aae103cd2aea..20f2659dd829256d7fef206087ab3262e1e291f5 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -472,7 +472,9 @@ struct sock_fprog_kern { struct bpf_binary_header { u16 pages; u16 locked:1; - u8 image[]; + + /* Some arches need word alignment for their instructions */ + u8 image[] __aligned(4); }; struct bpf_prog {
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 <edumazet@google.com> Cc: Daniel Borkmann <daniel@iogearbox.net> Cc: Martin KaFai Lau <kafai@fb.com> Cc: Alexei Starovoitov <ast@kernel.org> --- include/linux/filter.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)