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| author | Viktor Malik <vmalik@redhat.com> | 2023-03-10 10:40:59 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2023-03-16 04:38:21 +0300 |
| commit | 31bf1dbccfb0a9861d4846755096b3fff5687f8a (patch) | |
| tree | 55c0c006460218032d79147cfc1a6121d7ecdce2 /kernel/bpf/syscall.c | |
| parent | b8a2e3f93d412114a1539ea97b59b3e6ed6e1f9a (diff) | |
| download | linux-31bf1dbccfb0a9861d4846755096b3fff5687f8a.tar.xz | |
bpf: Fix attaching fentry/fexit/fmod_ret/lsm to modules
This resolves two problems with attachment of fentry/fexit/fmod_ret/lsm
to functions located in modules:
1. The verifier tries to find the address to attach to in kallsyms. This
is always done by searching the entire kallsyms, not respecting the
module in which the function is located. Such approach causes an
incorrect attachment address to be computed if the function to attach
to is shadowed by a function of the same name located earlier in
kallsyms.
2. If the address to attach to is located in a module, the module
reference is only acquired in register_fentry. If the module is
unloaded between the place where the address is found
(bpf_check_attach_target in the verifier) and register_fentry, it is
possible that another module is loaded to the same address which may
lead to potential errors.
Since the attachment must contain the BTF of the program to attach to,
we extract the module from it and search for the function address in the
correct module (resolving problem no. 1). Then, the module reference is
taken directly in bpf_check_attach_target and stored in the bpf program
(in bpf_prog_aux). The reference is only released when the program is
unloaded (resolving problem no. 2).
Signed-off-by: Viktor Malik <vmalik@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/3f6a9d8ae850532b5ef864ef16327b0f7a669063.1678432753.git.vmalik@redhat.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf/syscall.c')
| -rw-r--r-- | kernel/bpf/syscall.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 5b88301a2ae0..099e9068bcdd 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2067,6 +2067,7 @@ static void __bpf_prog_put_noref(struct bpf_prog *prog, bool deferred) { bpf_prog_kallsyms_del_all(prog); btf_put(prog->aux->btf); + module_put(prog->aux->mod); kvfree(prog->aux->jited_linfo); kvfree(prog->aux->linfo); kfree(prog->aux->kfunc_tab); @@ -3113,6 +3114,11 @@ static int bpf_tracing_prog_attach(struct bpf_prog *prog, if (err) goto out_unlock; + if (tgt_info.tgt_mod) { + module_put(prog->aux->mod); + prog->aux->mod = tgt_info.tgt_mod; + } + tr = bpf_trampoline_get(key, &tgt_info); if (!tr) { err = -ENOMEM; |