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@csgroup.eu>
Cc: linux-hardening@vger.kernel.org <linux-hardening@vger.kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Message-ID: <286def78955e04382b227cb3e4b6ba272a7442e3.1709850515.git.christophe.leroy@csgroup.eu>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index c99bc3df2d28e35f73b21d62ca50f4a53c515e1b..9107ee1de66faa3b07a0451da72d397fca64c6ed 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -887,14 +887,15 @@ 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 696bc55de8e82ea9358ede9c222b4927871e60be..63f100def31bcee9dac2df5c25aa5288ea23f29f 100644 (file)
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2403,7 +2403,9 @@ 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 7b208e5d38f65f79a259d78de50cfc428e08add4..de7813947981a15774cfa630966e997e15753659 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19263,10 +19263,14 @@ 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]);
-               bpf_prog_kallsyms_add(func[i]);
+               err = bpf_prog_lock_ro(func[i]);
+               if (err)
+                       goto out_free;
        }
 
+       for (i = 1; 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.