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authorDaniel Borkmann <daniel@iogearbox.net>2017-01-13 23:38:15 +0100
committerDavid S. Miller <davem@davemloft.net>2017-01-16 14:03:31 -0500
commitf1f7714ea51c56b7163fb1a5acf39c6a204dd758 (patch)
tree9e1d9aeda7fe5b358c6d7ed71ccfcdcd576f313a /kernel
parent57d5f64d83ab5b5a5118b1597386dd76eaf4340d (diff)
downloadlinux-f1f7714ea51c56b7163fb1a5acf39c6a204dd758.tar.bz2
bpf: rework prog_digest into prog_tag
Commit 7bd509e311f4 ("bpf: add prog_digest and expose it via fdinfo/netlink") was recently discussed, partially due to admittedly suboptimal name of "prog_digest" in combination with sha1 hash usage, thus inevitably and rightfully concerns about its security in terms of collision resistance were raised with regards to use-cases. The intended use cases are for debugging resp. introspection only for providing a stable "tag" over the instruction sequence that both kernel and user space can calculate independently. It's not usable at all for making a security relevant decision. So collisions where two different instruction sequences generate the same tag can happen, but ideally at a rather low rate. The "tag" will be dumped in hex and is short enough to introspect in tracepoints or kallsyms output along with other data such as stack trace, etc. Thus, this patch performs a rename into prog_tag and truncates the tag to a short output (64 bits) to make it obvious it's not collision-free. Should in future a hash or facility be needed with a security relevant focus, then we can think about requirements, constraints, etc that would fit to that situation. For now, rework the exposed parts for the current use cases as long as nothing has been released yet. Tested on x86_64 and s390x. Fixes: 7bd509e311f4 ("bpf: add prog_digest and expose it via fdinfo/netlink") Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/bpf/core.c14
-rw-r--r--kernel/bpf/syscall.c8
-rw-r--r--kernel/bpf/verifier.c2
3 files changed, 13 insertions, 11 deletions
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 1eb4f1303756..503d4211988a 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -146,10 +146,11 @@ void __bpf_prog_free(struct bpf_prog *fp)
vfree(fp);
}
-int bpf_prog_calc_digest(struct bpf_prog *fp)
+int bpf_prog_calc_tag(struct bpf_prog *fp)
{
const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64);
- u32 raw_size = bpf_prog_digest_scratch_size(fp);
+ u32 raw_size = bpf_prog_tag_scratch_size(fp);
+ u32 digest[SHA_DIGEST_WORDS];
u32 ws[SHA_WORKSPACE_WORDS];
u32 i, bsize, psize, blocks;
struct bpf_insn *dst;
@@ -162,7 +163,7 @@ int bpf_prog_calc_digest(struct bpf_prog *fp)
if (!raw)
return -ENOMEM;
- sha_init(fp->digest);
+ sha_init(digest);
memset(ws, 0, sizeof(ws));
/* We need to take out the map fd for the digest calculation
@@ -204,13 +205,14 @@ int bpf_prog_calc_digest(struct bpf_prog *fp)
*bits = cpu_to_be64((psize - 1) << 3);
while (blocks--) {
- sha_transform(fp->digest, todo, ws);
+ sha_transform(digest, todo, ws);
todo += SHA_MESSAGE_BYTES;
}
- result = (__force __be32 *)fp->digest;
+ result = (__force __be32 *)digest;
for (i = 0; i < SHA_DIGEST_WORDS; i++)
- result[i] = cpu_to_be32(fp->digest[i]);
+ result[i] = cpu_to_be32(digest[i]);
+ memcpy(fp->tag, result, sizeof(fp->tag));
vfree(raw);
return 0;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e89acea22ecf..1d6b29e4e2c3 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -688,17 +688,17 @@ static int bpf_prog_release(struct inode *inode, struct file *filp)
static void bpf_prog_show_fdinfo(struct seq_file *m, struct file *filp)
{
const struct bpf_prog *prog = filp->private_data;
- char prog_digest[sizeof(prog->digest) * 2 + 1] = { };
+ char prog_tag[sizeof(prog->tag) * 2 + 1] = { };
- bin2hex(prog_digest, prog->digest, sizeof(prog->digest));
+ bin2hex(prog_tag, prog->tag, sizeof(prog->tag));
seq_printf(m,
"prog_type:\t%u\n"
"prog_jited:\t%u\n"
- "prog_digest:\t%s\n"
+ "prog_tag:\t%s\n"
"memlock:\t%llu\n",
prog->type,
prog->jited,
- prog_digest,
+ prog_tag,
prog->pages * 1ULL << PAGE_SHIFT);
}
#endif
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 83ed2f8f6f22..cdc43b899f28 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2936,7 +2936,7 @@ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env)
int insn_cnt = env->prog->len;
int i, j, err;
- err = bpf_prog_calc_digest(env->prog);
+ err = bpf_prog_calc_tag(env->prog);
if (err)
return err;