Merge branch 'bpf-fixes'

Daniel Borkmann says:

====================
First one is a panic I ran into while testing the second
one where we got several syzkaller reports. Series here
fixes both.

Thanks!
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>

3 files changed, 106 insertions, 38 deletions

diff --git a/include/linux/filter.h b/include/linux/filter.h
index 45fc0f5000d8..108f9812e196 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -469,7 +469,8 @@ struct sock_fprog_kern {
 };
 
 struct bpf_binary_header {
-	unsigned int pages;
+	u16 pages;
+	u16 locked:1;
 	u8 image[];
 };
 
@@ -671,15 +672,18 @@ bpf_ctx_narrow_access_ok(u32 off, u32 size, u32 size_default)
 
 #define bpf_classic_proglen(fprog) (fprog->len * sizeof(fprog->filter[0]))
 
-#ifdef CONFIG_ARCH_HAS_SET_MEMORY
 static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
 {
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
 	fp->locked = 1;
-	WARN_ON_ONCE(set_memory_ro((unsigned long)fp, fp->pages));
+	if (set_memory_ro((unsigned long)fp, fp->pages))
+		fp->locked = 0;
+#endif
 }
 
 static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 {
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
 	if (fp->locked) {
 		WARN_ON_ONCE(set_memory_rw((unsigned long)fp, fp->pages));
 		/* In case set_memory_rw() fails, we want to be the first
@@ -687,34 +691,30 @@ static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
 		 */
 		fp->locked = 0;
 	}
+#endif
 }
 
 static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
 {
-	WARN_ON_ONCE(set_memory_ro((unsigned long)hdr, hdr->pages));
-}
-
-static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
-{
-	WARN_ON_ONCE(set_memory_rw((unsigned long)hdr, hdr->pages));
-}
-#else
-static inline void bpf_prog_lock_ro(struct bpf_prog *fp)
-{
-}
-
-static inline void bpf_prog_unlock_ro(struct bpf_prog *fp)
-{
-}
-
-static inline void bpf_jit_binary_lock_ro(struct bpf_binary_header *hdr)
-{
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
+	hdr->locked = 1;
+	if (set_memory_ro((unsigned long)hdr, hdr->pages))
+		hdr->locked = 0;
+#endif
 }
 
 static inline void bpf_jit_binary_unlock_ro(struct bpf_binary_header *hdr)
 {
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
+	if (hdr->locked) {
+		WARN_ON_ONCE(set_memory_rw((unsigned long)hdr, hdr->pages));
+		/* In case set_memory_rw() fails, we want to be the first
+		 * to crash here instead of some random place later on.
+		 */
+		hdr->locked = 0;
+	}
+#endif
 }
-#endif /* CONFIG_ARCH_HAS_SET_MEMORY */
 
 static inline struct bpf_binary_header *
 bpf_jit_binary_hdr(const struct bpf_prog *fp)
@@ -725,6 +725,22 @@ bpf_jit_binary_hdr(const struct bpf_prog *fp)
 	return (void *)addr;
 }
 
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
+static inline int bpf_prog_check_pages_ro_single(const struct bpf_prog *fp)
+{
+	if (!fp->locked)
+		return -ENOLCK;
+	if (fp->jited) {
+		const struct bpf_binary_header *hdr = bpf_jit_binary_hdr(fp);
+
+		if (!hdr->locked)
+			return -ENOLCK;
+	}
+
+	return 0;
+}
+#endif
+
 int sk_filter_trim_cap(struct sock *sk, struct sk_buff *skb, unsigned int cap);
 static inline int sk_filter(struct sock *sk, struct sk_buff *skb)
 {
@@ -961,6 +977,9 @@ static inline void bpf_prog_kallsyms_del(struct bpf_prog *fp)
 }
 #endif /* CONFIG_BPF_JIT */
 
+void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp);
+void bpf_prog_kallsyms_del_all(struct bpf_prog *fp);
+
 #define BPF_ANC		BIT(15)
 
 static inline bool bpf_needs_clear_a(const struct sock_filter *first)
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9f1493705f40..a9e6c04d0f4a 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -350,6 +350,20 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
 	return prog_adj;
 }
 
+void bpf_prog_kallsyms_del_subprogs(struct bpf_prog *fp)
+{
+	int i;
+
+	for (i = 0; i < fp->aux->func_cnt; i++)
+		bpf_prog_kallsyms_del(fp->aux->func[i]);
+}
+
+void bpf_prog_kallsyms_del_all(struct bpf_prog *fp)
+{
+	bpf_prog_kallsyms_del_subprogs(fp);
+	bpf_prog_kallsyms_del(fp);
+}
+
 #ifdef CONFIG_BPF_JIT
 /* All BPF JIT sysctl knobs here. */
 int bpf_jit_enable   __read_mostly = IS_BUILTIN(CONFIG_BPF_JIT_ALWAYS_ON);
@@ -584,6 +598,8 @@ bpf_jit_binary_alloc(unsigned int proglen, u8 **image_ptr,
 	bpf_fill_ill_insns(hdr, size);
 
 	hdr->pages = size / PAGE_SIZE;
+	hdr->locked = 0;
+
 	hole = min_t(unsigned int, size - (proglen + sizeof(*hdr)),
 		     PAGE_SIZE - sizeof(*hdr));
 	start = (get_random_int() % hole) & ~(alignment - 1);
@@ -1434,6 +1450,33 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
 	return 0;
 }
 
+static int bpf_prog_check_pages_ro_locked(const struct bpf_prog *fp)
+{
+#ifdef CONFIG_ARCH_HAS_SET_MEMORY
+	int i, err;
+
+	for (i = 0; i < fp->aux->func_cnt; i++) {
+		err = bpf_prog_check_pages_ro_single(fp->aux->func[i]);
+		if (err)
+			return err;
+	}
+
+	return bpf_prog_check_pages_ro_single(fp);
+#endif
+	return 0;
+}
+
+static void bpf_prog_select_func(struct bpf_prog *fp)
+{
+#ifndef CONFIG_BPF_JIT_ALWAYS_ON
+	u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1);
+
+	fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1];
+#else
+	fp->bpf_func = __bpf_prog_ret0_warn;
+#endif
+}
+
 /**
  *	bpf_prog_select_runtime - select exec runtime for BPF program
  *	@fp: bpf_prog populated with internal BPF program
@@ -1444,13 +1487,13 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
  */
 struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 {
-#ifndef CONFIG_BPF_JIT_ALWAYS_ON
-	u32 stack_depth = max_t(u32, fp->aux->stack_depth, 1);
+	/* In case of BPF to BPF calls, verifier did all the prep
+	 * work with regards to JITing, etc.
+	 */
+	if (fp->bpf_func)
+		goto finalize;
 
-	fp->bpf_func = interpreters[(round_up(stack_depth, 32) / 32) - 1];
-#else
-	fp->bpf_func = __bpf_prog_ret0_warn;
-#endif
+	bpf_prog_select_func(fp);
 
 	/* eBPF JITs can rewrite the program in case constant
 	 * blinding is active. However, in case of error during
@@ -1471,6 +1514,8 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 		if (*err)
 			return fp;
 	}
+
+finalize:
 	bpf_prog_lock_ro(fp);
 
 	/* The tail call compatibility check can only be done at
@@ -1479,7 +1524,17 @@ struct bpf_prog *bpf_prog_select_runtime(struct bpf_prog *fp, int *err)
 	 * all eBPF JITs might immediately support all features.
 	 */
 	*err = bpf_check_tail_call(fp);
-
+	if (*err)
+		return fp;
+
+	/* Checkpoint: at this point onwards any cBPF -> eBPF or
+	 * native eBPF program is read-only. If we failed to change
+	 * the page attributes (e.g. allocation failure from
+	 * splitting large pages), then reject the whole program
+	 * in order to guarantee not ending up with any W+X pages
+	 * from BPF side in kernel.
+	 */
+	*err = bpf_prog_check_pages_ro_locked(fp);
 	return fp;
 }
 EXPORT_SYMBOL_GPL(bpf_prog_select_runtime);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0fa20624707f..35dc466641f2 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1034,14 +1034,9 @@ static void __bpf_prog_put_rcu(struct rcu_head *rcu)
 static void __bpf_prog_put(struct bpf_prog *prog, bool do_idr_lock)
 {
 	if (atomic_dec_and_test(&prog->aux->refcnt)) {
-		int i;
-
 		/* bpf_prog_free_id() must be called first */
 		bpf_prog_free_id(prog, do_idr_lock);
-
-		for (i = 0; i < prog->aux->func_cnt; i++)
-			bpf_prog_kallsyms_del(prog->aux->func[i]);
-		bpf_prog_kallsyms_del(prog);
+		bpf_prog_kallsyms_del_all(prog);
 
 		call_rcu(&prog->aux->rcu, __bpf_prog_put_rcu);
 	}
@@ -1358,9 +1353,7 @@ static int bpf_prog_load(union bpf_attr *attr)
 	if (err < 0)
 		goto free_used_maps;
 
-	/* eBPF program is ready to be JITed */
-	if (!prog->bpf_func)
-		prog = bpf_prog_select_runtime(prog, &err);
+	prog = bpf_prog_select_runtime(prog, &err);
 	if (err < 0)
 		goto free_used_maps;
 
@@ -1384,6 +1377,7 @@ static int bpf_prog_load(union bpf_attr *attr)
 	return err;
 
 free_used_maps:
+	bpf_prog_kallsyms_del_subprogs(prog);
 	free_used_maps(prog->aux);
 free_prog:
 	bpf_prog_uncharge_memlock(prog);