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authorDavid Miller <davem@davemloft.net>2018-11-30 21:08:14 -0800
committerAlexei Starovoitov <ast@kernel.org>2018-11-30 21:38:48 -0800
commite9ee9efc0d176512cdce9d27ff8549d7ffa2bfcd (patch)
tree94b32bfcaa32c3538810330370ed7cd4b07e15e4 /kernel/bpf
parent88945f460603ad8909b556c67a9229bb23188d41 (diff)
downloadlinux-e9ee9efc0d176512cdce9d27ff8549d7ffa2bfcd.tar.bz2
bpf: Add BPF_F_ANY_ALIGNMENT.
Often we want to write tests cases that check things like bad context offset accesses. And one way to do this is to use an odd offset on, for example, a 32-bit load. This unfortunately triggers the alignment checks first on platforms that do not set CONFIG_EFFICIENT_UNALIGNED_ACCESS. So the test case see the alignment failure rather than what it was testing for. It is often not completely possible to respect the original intention of the test, or even test the same exact thing, while solving the alignment issue. Another option could have been to check the alignment after the context and other validations are performed by the verifier, but that is a non-trivial change to the verifier. Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/syscall.c7
-rw-r--r--kernel/bpf/verifier.c2
2 files changed, 8 insertions, 1 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 85cbeec06e50..f9554d9a14e1 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1452,9 +1452,14 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
if (CHECK_ATTR(BPF_PROG_LOAD))
return -EINVAL;
- if (attr->prog_flags & ~BPF_F_STRICT_ALIGNMENT)
+ if (attr->prog_flags & ~(BPF_F_STRICT_ALIGNMENT | BPF_F_ANY_ALIGNMENT))
return -EINVAL;
+ if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
+ (attr->prog_flags & BPF_F_ANY_ALIGNMENT) &&
+ !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
/* copy eBPF program license from user space */
if (strncpy_from_user(license, u64_to_user_ptr(attr->license),
sizeof(license) - 1) < 0)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9584438fa2cc..71988337ac14 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -6505,6 +6505,8 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr,
env->strict_alignment = !!(attr->prog_flags & BPF_F_STRICT_ALIGNMENT);
if (!IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS))
env->strict_alignment = true;
+ if (attr->prog_flags & BPF_F_ANY_ALIGNMENT)
+ env->strict_alignment = false;
ret = replace_map_fd_with_map_ptr(env);
if (ret < 0)