linux-hardening - [PATCH bpf-next v2 1/2] bpf: Take return from set_memory_ro() into account with bpf_prog_lock

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Message-ID: <8f3b3823cce2177e5912ff5f2f11381a16db07db.1709279160.git.christophe.leroy@csgroup.eu>
Date: Fri,  1 Mar 2024 08:52:24 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	KP Singh <kpsingh@...nel.org>,
	Stanislav Fomichev <sdf@...gle.com>,
	Hao Luo <haoluo@...gle.com>,
	Jiri Olsa <jolsa@...nel.org>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	bpf@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev,
	linux-mips@...r.kernel.org,
	linux-parisc@...r.kernel.org,
	linux-s390@...r.kernel.org,
	sparclinux@...r.kernel.org,
	netdev@...r.kernel.org,
	"linux-hardening @ vger . kernel . org" <linux-hardening@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>
Subject: [PATCH bpf-next v2 1/2] bpf: Take return from set_memory_ro() into account with bpf_prog_lock_ro()

set_memory_ro() can fail, leaving memory unprotected.

Check its return and take it into account as an error.

Link: https://github.com/KSPP/linux/issues/7
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: linux-hardening@...r.kernel.org <linux-hardening@...r.kernel.org>
Reviewed-by: Kees Cook <keescook@...omium.org>
---
Note: next patch is autonomous, it is sent as a follow-up of this one to minimize risk of conflict on filter.h because the two changes are too close to each other.

v2: No modification (Just added link in patch message), patchwork discarded this series due to failed test of s390 but it seems unrelated, see https://lore.kernel.org/bpf/wvd5gzde5ejc2rzsbrtwqyof56uw5ea3rxntfrxtkdabzcuwt6@w7iczzhmay2i/T/#m2e61446f42d5dc3d78f2e0e8b7a783f15cfb109d
---
 include/linux/filter.h | 5 +++--
 kernel/bpf/core.c      | 4 +++-
 kernel/bpf/verifier.c  | 4 +++-
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 36cc29a2934c..7dd59bccaeec 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -884,14 +884,15 @@ bpf_ctx_narrow_access_offset(u32 off, u32 size, u32 size_default)
 
 #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
 
-static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
+static inline int __must_check bpf_prog_lock_ro(struct bpf_prog *fp)
 {
 #ifndef CONFIG_BPF_JIT_ALWAYS_ON
 	if (!fp->jited) {
 		set_vm_flush_reset_perms(fp);
-		set_memory_ro((unsigned long)fp, fp->pages);
+		return set_memory_ro((unsigned long)fp, fp->pages);
 	}
 #endif
+	return 0;
 }
 
 static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 71c459a51d9e..c49619ef55d0 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2392,7 +2392,9 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 	}
 
 finalize:
-	bpf_prog_lock_ro(fp);
+	*err = bpf_prog_lock_ro(fp);
+	if (*err)
+		return fp;
 
 	/* The tail call compatibility check can only be done at
 	 * this late stage as we need to determine, if we deal
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1c34b91b9583..6ec134f76a11 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19096,7 +19096,9 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 	 * bpf_prog_load will add the kallsyms for the main program.
 	 */
 	for (i = 1; i < env->subprog_cnt; i++) {
-		bpf_prog_lock_ro(func[i]);
+		err = bpf_prog_lock_ro(func[i]);
+		if (err)
+			goto out_free;
 		bpf_prog_kallsyms_add(func[i]);
 	}
 
-- 
2.43.0