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authorDaniel Borkmann <daniel@iogearbox.net>2016-12-07 01:15:44 +0100
committerDavid S. Miller <davem@davemloft.net>2016-12-07 13:16:04 -0500
commitef0915cacd04c9e35be5f9d62a4e4b5b4b9bcfd1 (patch)
treeb3589bba5b7632cc8e763ce614bc5af35d58bc36 /kernel
parent90364feaf70f251533feff3f228f82df9a9f52b6 (diff)
downloadlinux-ef0915cacd04c9e35be5f9d62a4e4b5b4b9bcfd1.tar.bz2
bpf: fix loading of BPF_MAXINSNS sized programs
General assumption is that single program can hold up to BPF_MAXINSNS, that is, 4096 number of instructions. It is the case with cBPF and that limit was carried over to eBPF. When recently testing digest, I noticed that it's actually not possible to feed 4096 instructions via bpf(2). The check for > BPF_MAXINSNS was added back then to bpf_check() in cbd357008604 ("bpf: verifier (add ability to receive verification log)"). However, 09756af46893 ("bpf: expand BPF syscall with program load/unload") added yet another check that comes before that into bpf_prog_load(), but this time bails out already in case of >= BPF_MAXINSNS. Fix it up and perform the check early in bpf_prog_load(), so we can drop the second one in bpf_check(). It makes sense, because also a 0 insn program is useless and we don't want to waste any resources doing work up to bpf_check() point. The existing bpf(2) man page documents E2BIG as the official error for such cases, so just stick with it as well. Fixes: 09756af46893 ("bpf: expand BPF syscall with program load/unload") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/syscall.c4
-rw-r--r--kernel/bpf/verifier.c3
2 files changed, 2 insertions, 5 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index c0d2b423ce93..88f609f1c0c3 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -786,8 +786,8 @@ static int bpf_prog_load(union bpf_attr *attr)
/* eBPF programs must be GPL compatible to use GPL-ed functions */
is_gpl = license_is_gpl_compatible(license);
- if (attr->insn_cnt >= BPF_MAXINSNS)
- return -EINVAL;
+ if (attr->insn_cnt == 0 || attr->insn_cnt > BPF_MAXINSNS)
+ return -E2BIG;
if (type == BPF_PROG_TYPE_KPROBE &&
attr->kern_version != LINUX_VERSION_CODE)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cb37339ca0da..da9fb2a9b7eb 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3133,9 +3133,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr)
struct bpf_verifier_env *env;
int ret = -EINVAL;
- if ((*prog)->len <= 0 || (*prog)->len > BPF_MAXINSNS)
- return -E2BIG;
-
/* 'struct bpf_verifier_env' can be global, but since it's not small,
* allocate/free it every time bpf_check() is called
*/