summaryrefslogtreecommitdiffstats
path: root/kernel/bpf/cgroup.c
diff options
context:
space:
mode:
authorYonghong Song <yhs@fb.com>2017-12-18 10:13:44 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2017-12-19 01:43:29 +0100
commit06ef0ccb5a36e1feba9b413ff59a04ecc4407c1c (patch)
treec8fae1e963a0468ce1cf803b92bb95c54d2a9775 /kernel/bpf/cgroup.c
parentc060bc6115b6a204cb60e6b03fe64135731bc6c8 (diff)
downloadlinux-06ef0ccb5a36e1feba9b413ff59a04ecc4407c1c.tar.bz2
bpf/cgroup: fix a verification error for a CGROUP_DEVICE type prog
The tools/testing/selftests/bpf test program test_dev_cgroup fails with the following error when compiled with llvm 6.0. (I did not try with earlier versions.) libbpf: load bpf program failed: Permission denied libbpf: -- BEGIN DUMP LOG --- libbpf: 0: (61) r2 = *(u32 *)(r1 +4) 1: (b7) r0 = 0 2: (55) if r2 != 0x1 goto pc+8 R0=inv0 R1=ctx(id=0,off=0,imm=0) R2=inv1 R10=fp0 3: (69) r2 = *(u16 *)(r1 +0) invalid bpf_context access off=0 size=2 ... The culprit is the following statement in dev_cgroup.c: short type = ctx->access_type & 0xFFFF; This code is typical as the ctx->access_type is assigned as below in kernel/bpf/cgroup.c: struct bpf_cgroup_dev_ctx ctx = { .access_type = (access << 16) | dev_type, .major = major, .minor = minor, }; The compiler converts it to u16 access while the verifier cgroup_dev_is_valid_access rejects any non u32 access. This patch permits the field access_type to be accessible with type u16 and u8 as well. Signed-off-by: Yonghong Song <yhs@fb.com> Tested-by: Roman Gushchin <guro@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Diffstat (limited to 'kernel/bpf/cgroup.c')
-rw-r--r--kernel/bpf/cgroup.c15
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index b789ab78d28f..c1c0b60d3f2f 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -568,6 +568,8 @@ static bool cgroup_dev_is_valid_access(int off, int size,
enum bpf_access_type type,
struct bpf_insn_access_aux *info)
{
+ const int size_default = sizeof(__u32);
+
if (type == BPF_WRITE)
return false;
@@ -576,8 +578,17 @@ static bool cgroup_dev_is_valid_access(int off, int size,
/* The verifier guarantees that size > 0. */
if (off % size != 0)
return false;
- if (size != sizeof(__u32))
- return false;
+
+ switch (off) {
+ case bpf_ctx_range(struct bpf_cgroup_dev_ctx, access_type):
+ bpf_ctx_record_field_size(info, size_default);
+ if (!bpf_ctx_narrow_access_ok(off, size, size_default))
+ return false;
+ break;
+ default:
+ if (size != size_default)
+ return false;
+ }
return true;
}