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Fri, 9 Jun 2023 14:40:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=templeofstupid.com; s=dreamhost; t=1686346809; bh=u6VFkU8CeRSXxG9CpKygUWaCfdMHq1wUPGyeNaB+TlE=; h=Date:From:To:Cc:Subject:Content-Type; b=Iyv1QSXdQRbIWJQoNqScr1eFgnvlDibXQ2N/j+Rghgo11nkvnTKr+NuMf+YgJ8tYb AwT8Hv6fI5B9CmxFLyrB2X2or1ckwfM+ikaRFmxQNjmgV1/b0ah/DBZCvZ8356O+9l UegCkqq/hwdeSAjg+Rp6Sfdrrs7p8Eu6AJdRAdp0= Received: from johansen (uid 1000) (envelope-from kjlx@templeofstupid.com) id e00d9 by kmjvbox (DragonFly Mail Agent v0.12); Fri, 09 Jun 2023 14:40:07 -0700 Date: Fri, 9 Jun 2023 14:40:07 -0700 From: Krister Johansen To: bpf@vger.kernel.org Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Mykola Lysenko , Shuah Khan , linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH bpf v4 1/2] bpf: ensure main program has an extable Message-ID: <9253ce691956f19adc93be7dc4c3a7aabe3db3de.1686345886.git.kjlx@templeofstupid.com> References: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org When subprograms are in use, the main program is not jit'd after the subprograms because jit_subprogs sets a value for prog->bpf_func upon success. Subsequent calls to the JIT are bypassed when this value is non-NULL. This leads to a situation where the main program and its func[0] counterpart are both in the bpf kallsyms tree, but only func[0] has an extable. Extables are only created during JIT. Now there are two nearly identical program ksym entries in the tree, but only one has an extable. Depending upon how the entries are placed, there's a chance that a fault will call search_extable on the aux with the NULL entry. Since jit_subprogs already copies state from func[0] to the main program, include the extable pointer in this state duplication. Additionally, ensure that the copy of the main program in func[0] is not added to the bpf_prog_kallsyms table. Instead, let the main program get added later in bpf_prog_load(). This ensures there is only a single copy of the main program in the kallsyms table, and that its tag matches the tag observed by tooling like bpftool. Cc: stable@vger.kernel.org Fixes: 1c2a088a6626 ("bpf: x64: add JIT support for multi-function programs") Signed-off-by: Krister Johansen Acked-by: Yonghong Song --- kernel/bpf/verifier.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 5871aa78d01a..b62d1fc0f92b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -17214,9 +17214,10 @@ static int jit_subprogs(struct bpf_verifier_env *env) } /* finally lock prog and jit images for all functions and - * populate kallsysm + * populate kallsysm. Begin at the first subprogram, since + * bpf_prog_load will add the kallsyms for the main program. */ - for (i = 0; i < env->subprog_cnt; i++) { + for (i = 1; i < env->subprog_cnt; i++) { bpf_prog_lock_ro(func[i]); bpf_prog_kallsyms_add(func[i]); } @@ -17242,6 +17243,7 @@ static int jit_subprogs(struct bpf_verifier_env *env) prog->jited = 1; prog->bpf_func = func[0]->bpf_func; prog->jited_len = func[0]->jited_len; + prog->aux->extable = func[0]->aux->extable; prog->aux->func = func; prog->aux->func_cnt = env->subprog_cnt; bpf_prog_jit_attempt_done(prog);