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| author |   Kumar Kartikeya Dwivedi <memxor@gmail.com> | 2021-10-09 09:39:00 +0530 |
|---|---|---|
| committer |   Andrii Nakryiko <andrii@kernel.org> | 2021-10-19 16:55:50 -0700 |
| commit | 588cd7ef5382eb89d09a64ee9ba85e4f9a5b0bcb (patch) | |
| tree | bb91099b7f7e6196525896fa9b4e06ee64466e66 /kernel/bpf | |
| parent | Merge branch 'fixes for bpftool's Makefile' (diff) | |
| download | linux-dev-588cd7ef5382eb89d09a64ee9ba85e4f9a5b0bcb.tar.xz linux-dev-588cd7ef5382eb89d09a64ee9ba85e4f9a5b0bcb.zip | |
bpf: Silence Coverity warning for find_kfunc_desc_btf
The helper function returns a pointer that in the failure case encodes
an error in the struct btf pointer. The current code lead to Coverity
warning about the use of the invalid pointer:
*** CID 1507963: Memory - illegal accesses (USE_AFTER_FREE)
/kernel/bpf/verifier.c: 1788 in find_kfunc_desc_btf()
1782 return ERR_PTR(-EINVAL);
1783 }
1784
1785 kfunc_btf = __find_kfunc_desc_btf(env, offset, btf_modp);
1786 if (IS_ERR_OR_NULL(kfunc_btf)) {
1787 verbose(env, "cannot find module BTF for func_id %u\n", func_id);
>>> CID 1507963: Memory - illegal accesses (USE_AFTER_FREE)
>>> Using freed pointer "kfunc_btf".
1788 return kfunc_btf ?: ERR_PTR(-ENOENT);
1789 }
1790 return kfunc_btf;
1791 }
1792 return btf_vmlinux ?: ERR_PTR(-ENOENT);
1793 }
Daniel suggested the use of ERR_CAST so that the intended use is clear
to Coverity, but on closer look it seems that we never return NULL from
the helper. Andrii noted that since __find_kfunc_desc_btf already logs
errors for all cases except btf_get_by_fd, it is much easier to add
logging for that and remove the IS_ERR check altogether, returning
directly from it.
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211009040900.803436-1-memxor@gmail.com
Diffstat (limited to 'kernel/bpf')
| -rw-r--r-- | kernel/bpf/verifier.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 20900a1bac12..21cdff35a2f9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1727,8 +1727,10 @@ static struct btf *__find_kfunc_desc_btf(struct bpf_verifier_env *env, return ERR_PTR(-EFAULT); btf = btf_get_by_fd(btf_fd); - if (IS_ERR(btf)) + if (IS_ERR(btf)) { + verbose(env, "invalid module BTF fd specified\n"); return btf; + } if (!btf_is_module(btf)) { verbose(env, "BTF fd for kfunc is not a module BTF\n"); @@ -1771,8 +1773,6 @@ static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env, u32 func_id, s16 offset, struct module **btf_modp) { - struct btf *kfunc_btf; - if (offset) { if (offset < 0) { /* In the future, this can be allowed to increase limit @@ -1782,12 +1782,7 @@ static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env, return ERR_PTR(-EINVAL); } - kfunc_btf = __find_kfunc_desc_btf(env, offset, btf_modp); - if (IS_ERR_OR_NULL(kfunc_btf)) { - verbose(env, "cannot find module BTF for func_id %u\n", func_id); - return kfunc_btf ?: ERR_PTR(-ENOENT); - } - return kfunc_btf; + return __find_kfunc_desc_btf(env, offset, btf_modp); } return btf_vmlinux ?: ERR_PTR(-ENOENT); } |