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| author | Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2023-09-13 01:32:04 +0200 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-09-16 18:34:21 +0200 |
| commit | b62bf8a5e9110922f58f6ea8fe747e1759f49e61 (patch) | |
| tree | b5992be840bc234adc2157ec1f62fa4e14b8bd62 /kernel | |
| parent | bpf: Add support for custom exception callbacks (diff) | |
| download | linux-b62bf8a5e9110922f58f6ea8fe747e1759f49e61.tar.xz linux-b62bf8a5e9110922f58f6ea8fe747e1759f49e61.zip | |
bpf: Perform CFG walk for exception callback
Since exception callbacks are not referenced using bpf_pseudo_func and
bpf_pseudo_call instructions, check_cfg traversal will never explore
instructions of the exception callback. Even after adding the subprog,
the program will then fail with a 'unreachable insn' error.
We thus need to begin walking from the start of the exception callback
again in check_cfg after a complete CFG traversal finishes, so as to
explore the CFG rooted at the exception callback.
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://lore.kernel.org/r/20230912233214.1518551-8-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/bpf/verifier.c | 15 |
1 files changed, 13 insertions, 2 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index ec3f22312516..863e4e6c4616 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -15126,8 +15126,8 @@ static int check_cfg(struct bpf_verifier_env *env) { int insn_cnt = env->prog->len; int *insn_stack, *insn_state; - int ret = 0; - int i; + int ex_insn_beg, i, ret = 0; + bool ex_done = false; insn_state = env->cfg.insn_state = kvcalloc(insn_cnt, sizeof(int), GFP_KERNEL); if (!insn_state) @@ -15143,6 +15143,7 @@ static int check_cfg(struct bpf_verifier_env *env) insn_stack[0] = 0; /* 0 is the first instruction */ env->cfg.cur_stack = 1; +walk_cfg: while (env->cfg.cur_stack > 0) { int t = insn_stack[env->cfg.cur_stack - 1]; @@ -15169,6 +15170,16 @@ static int check_cfg(struct bpf_verifier_env *env) goto err_free; } + if (env->exception_callback_subprog && !ex_done) { + ex_insn_beg = env->subprog_info[env->exception_callback_subprog].start; + + insn_state[ex_insn_beg] = DISCOVERED; + insn_stack[0] = ex_insn_beg; + env->cfg.cur_stack = 1; + ex_done = true; + goto walk_cfg; + } + for (i = 0; i < insn_cnt; i++) { if (insn_state[i] != EXPLORED) { verbose(env, "unreachable insn %d\n", i); |