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bpf: verbose jump offset overflow check 

Larger programs may trigger 16-bit jump offset overflow check
during instruction patching. Make this error verbose otherwise
users cannot decipher error code without printks in the verifier.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Alexei Starovoitov 2019-04-01 21:27:44 -07:00 committed by Daniel Borkmann
parent 71dde681a8
commit 4f73379ec5
2 changed files with 12 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

11
kernel/bpf/core.c
View File

@ -438,6 +438,7 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
u32 insn_adj_cnt, insn_rest, insn_delta = len - 1;
const u32 cnt_max = S16_MAX;
struct bpf_prog *prog_adj;
int err;
/* Since our patchlet doesn't expand the image, we're done. */
if (insn_delta == 0) {
@ -453,8 +454,8 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
* we afterwards may not fail anymore.
*/
if (insn_adj_cnt > cnt_max &&
bpf_adj_branches(prog, off, off + 1, off + len, true))
return NULL;
(err = bpf_adj_branches(prog, off, off + 1, off + len, true)))
return ERR_PTR(err);
/* Several new instructions need to be inserted. Make room
* for them. Likely, there's no need for a new allocation as
@ -463,7 +464,7 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt),
GFP_USER);
if (!prog_adj)
return NULL;
return ERR_PTR(-ENOMEM);
prog_adj->len = insn_adj_cnt;
@ -1096,13 +1097,13 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog)
continue;
tmp = bpf_patch_insn_single(clone, i, insn_buff, rewritten);
if (!tmp) {
if (IS_ERR(tmp)) {
/* Patching may have repointed aux->prog during
* realloc from the original one, so we need to
* fix it up here on error.
*/
bpf_jit_prog_release_other(prog, clone);
return ERR_PTR(-ENOMEM);
return tmp;
}
clone = tmp;

7
kernel/bpf/verifier.c
View File

@ -6932,8 +6932,13 @@ static struct bpf_prog *bpf_patch_insn_data(struct bpf_verifier_env *env, u32 of
struct bpf_prog *new_prog;
new_prog = bpf_patch_insn_single(env->prog, off, patch, len);
if (!new_prog)
if (IS_ERR(new_prog)) {
if (PTR_ERR(new_prog) == -ERANGE)
verbose(env,
"insn %d cannot be patched due to 16-bit range\n",
env->insn_aux_data[off].orig_idx);
return NULL;
}
if (adjust_insn_aux_data(env, new_prog->len, off, len))
return NULL;
adjust_subprog_starts(env, off, len);