[SRU][F][PATCH 1/1] bpf: Take return from set_memory_ro() into account with bpf_prog_lock_ro()

[Massimiliano Pellizzer]

From: Christophe Leroy <christophe.leroy at csgroup.eu>

[ Upstream commit 7d2cc63eca0c993c99d18893214abf8f85d566d8 ]

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 at csgroup.eu>
Cc: linux-hardening at vger.kernel.org <linux-hardening at vger.kernel.org>
Reviewed-by: Kees Cook <keescook at chromium.org>
Message-ID: <286def78955e04382b227cb3e4b6ba272a7442e3.1709850515.git.christophe.leroy at csgroup.eu>
Signed-off-by: Alexei Starovoitov <ast at kernel.org>
Signed-off-by: Sasha Levin <sashal at kernel.org>
(backported from commit 05412471beba313ecded95aa17b25fe84bb2551a linux-6.9.y)
[mpellizzer: backported solving minor merge conflict due to surrounding
instructions which do not affect the fix]
CVE-2024-42068
Signed-off-by: Massimiliano Pellizzer <massimiliano.pellizzer at canonical.com>
---
 include/linux/filter.h | 5 +++--
 kernel/bpf/core.c      | 4 +++-
 kernel/bpf/verifier.c  | 8 ++++++--
 3 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 0bec300b2e516..8134c256b276a 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -787,14 +787,15 @@ 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 dde21d23f2202..b9b45378bff54 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1787,7 +1787,9 @@ 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 5a375e28bfeaf..7776b1a6a24ce 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -9142,10 +9142,14 @@ static int jit_subprogs(struct bpf_verifier_env *env)
 	 * populate kallsysm
 	 */
 	for (i = 0; i < env->subprog_cnt; i++) {
-		bpf_prog_lock_ro(func[i]);
-		bpf_prog_kallsyms_add(func[i]);
+		err = bpf_prog_lock_ro(func[i]);
+		if (err)
+			goto out_free;
 	}
 
+	for (i = 0; i < env->subprog_cnt; i++)
+		bpf_prog_kallsyms_add(func[i]);
+
 	/* Last step: make now unused interpreter insns from main
 	 * prog consistent for later dump requests, so they can
 	 * later look the same as if they were interpreted only.
-- 
2.43.0