Re: [bpf-next 3/3] bpf: Fix a use after free in bpf_check()

Signed-off-by: He Fengqing <redacted>
---
 include/linux/filter.h |  2 +-
 kernel/bpf/core.c      |  9 ++++---
 kernel/bpf/verifier.c  | 53 ++++++++++++++++++++++++++++++++----------
 net/core/filter.c      |  2 +-
 4 files changed, 49 insertions(+), 17 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index f39e008a377d..ec11a5ae92c2 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h

@@ -881,7 +881,7 @@ void bpf_prog_jit_attempt_done(struct bpf_prog *prog);
 struct bpf_prog *bpf_prog_alloc(unsigned int size, gfp_t gfp_extra_flags);
 struct bpf_prog *bpf_prog_alloc_no_stats(unsigned int size, gfp_t gfp_extra_flags);
 struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
-                                 gfp_t gfp_extra_flags);
+                                 gfp_t gfp_extra_flags, bool free_old);
 void __bpf_prog_free(struct bpf_prog *fp);

 static inline void bpf_prog_clone_free(struct bpf_prog *fp)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 49b0311f48c1..e5616bb1665b 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c

@@ -218,7 +218,7 @@ void bpf_prog_fill_jited_linfo(struct bpf_prog *prog,
 }

 struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
-                                 gfp_t gfp_extra_flags)
+                                 gfp_t gfp_extra_flags, bool free_old)
 {
        gfp_t gfp_flags = GFP_KERNEL_ACCOUNT | __GFP_ZERO | gfp_extra_flags;
        struct bpf_prog *fp;

@@ -238,7 +238,8 @@ struct bpf_prog *bpf_prog_realloc(struct bpf_prog *fp_old, unsigned int size,
                /* We keep fp->aux from fp_old around in the new
                 * reallocated structure.
                 */
-               bpf_prog_clone_free(fp_old);
+               if (free_old)
+                       bpf_prog_clone_free(fp_old);
        }

        return fp;

@@ -456,7 +457,7 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
         * last page could have large enough tailroom.
         */
        prog_adj = bpf_prog_realloc(prog, bpf_prog_size(insn_adj_cnt),
-                                   GFP_USER);
+                                   GFP_USER, false);
        if (!prog_adj)
                return ERR_PTR(-ENOMEM);

@@ -1150,6 +1151,8 @@ struct bpf_prog *bpf_jit_blind_constants(struct bpf_prog *prog)
                        return tmp;
                }

+               if (tmp != clone)
+                       bpf_prog_clone_free(clone);
                clone = tmp;
                insn_delta = rewritten - 1;

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 41109f49b724..e75b933f69e4 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c

@@ -11855,7 +11855,10 @@ static int opt_subreg_zext_lo32_rnd_hi32(struct bpf_verifier_env *env,
                new_prog = bpf_patch_insn_data(env, adj_idx, patch, patch_len);
                if (!new_prog)
                        return -ENOMEM;
-               env->prog = new_prog;
+               if (new_prog != env->prog) {
+                       bpf_prog_clone_free(env->prog);
+                       env->prog = new_prog;
+               }

diff --git a/net/core/filter.c b/net/core/filter.c
index d70187ce851b..8a8d1a3ba5c2 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c

@@ -1268,7 +1268,7 @@ static struct bpf_prog *bpf_migrate_filter(struct bpf_prog *fp)

        /* Expand fp for appending the new filter representation. */
        old_fp = fp;
-       fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0);
+       fp = bpf_prog_realloc(old_fp, bpf_prog_size(new_len), 0, true);