[PATCH bpf-next 1/2] bpf: Take return from set_memory_ro() into account with bpf_prog_lock_ro()

[Christophe Leroy]

set_memory_ro() can fail, leaving memory unprotected.

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

Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu>
---
 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 fee070b9826e..fc0994dc5c72 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -881,14 +881,15 @@ 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 c5d68a9d8acc..1f831a6b4bbc 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -19020,7 +19020,9 @@ 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