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Commit aafe6ae9 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf: dynamically allocate digest scratch buffer 



Geert rightfully complained that 7bd509e3 ("bpf: add prog_digest
and expose it via fdinfo/netlink") added a too large allocation of
variable 'raw' from bss section, and should instead be done dynamically:

  # ./scripts/bloat-o-meter kernel/bpf/core.o.1 kernel/bpf/core.o.2
  add/remove: 3/0 grow/shrink: 0/0 up/down: 33291/0 (33291)
  function                                     old     new   delta
  raw                                            -   32832  +32832
  [...]

Since this is only relevant during program creation path, which can be
considered slow-path anyway, lets allocate that dynamically and be not
implicitly dependent on verifier mutex. Move bpf_prog_calc_digest() at
the beginning of replace_map_fd_with_map_ptr() and also error handling
stays straight forward.

Reported-by: default avatarGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 40e972ab

include/linux/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -216,7 +216,7 @@ u64 bpf_tail_call(u64 ctx, u64 r2, u64 index, u64 r4, u64 r5); 
u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5);



bool bpf_prog_array_compatible(struct bpf_array *array, const struct bpf_prog *fp);

void bpf_prog_calc_digest(struct bpf_prog *fp);

int bpf_prog_calc_digest(struct bpf_prog *fp);



const struct bpf_func_proto *bpf_get_trace_printk_proto(void);

include/linux/filter.h

+11 −3
Original line number Diff line number Diff line
@@ -57,9 +57,6 @@ struct bpf_prog_aux; 
/* BPF program can access up to 512 bytes of stack space. */

#define MAX_BPF_STACK	512



/* Maximum BPF program size in bytes. */

#define MAX_BPF_SIZE	(BPF_MAXINSNS * sizeof(struct bpf_insn))



/* Helper macros for filter block array initializers. */



/* ALU ops on registers, bpf_add|sub|...: dst_reg += src_reg */
@@ -517,6 +514,17 @@ static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog, 
	return BPF_PROG_RUN(prog, xdp);

}



static inline u32 bpf_prog_insn_size(const struct bpf_prog *prog)

{

	return prog->len * sizeof(struct bpf_insn);

}



static inline u32 bpf_prog_digest_scratch_size(const struct bpf_prog *prog)

{

	return round_up(bpf_prog_insn_size(prog) +

			sizeof(__be64) + 1, SHA_MESSAGE_BYTES);

}



static inline unsigned int bpf_prog_size(unsigned int proglen)

{

	return max(sizeof(struct bpf_prog),

kernel/bpf/core.c

+16 −11
Original line number Diff line number Diff line
@@ -136,28 +136,29 @@ void __bpf_prog_free(struct bpf_prog *fp) 
	vfree(fp);

}



#define SHA_BPF_RAW_SIZE						\

	round_up(MAX_BPF_SIZE + sizeof(__be64) + 1, SHA_MESSAGE_BYTES)



/* Called under verifier mutex. */

void bpf_prog_calc_digest(struct bpf_prog *fp)

int bpf_prog_calc_digest(struct bpf_prog *fp)

{

	const u32 bits_offset = SHA_MESSAGE_BYTES - sizeof(__be64);

	static u32 ws[SHA_WORKSPACE_WORDS];

	static u8 raw[SHA_BPF_RAW_SIZE];

	struct bpf_insn *dst = (void *)raw;

	u32 raw_size = bpf_prog_digest_scratch_size(fp);

	u32 ws[SHA_WORKSPACE_WORDS];

	u32 i, bsize, psize, blocks;

	struct bpf_insn *dst;

	bool was_ld_map;

	u8 *todo = raw;

	u8 *raw, *todo;

	__be32 *result;

	__be64 *bits;



	raw = vmalloc(raw_size);

	if (!raw)

		return -ENOMEM;



	sha_init(fp->digest);

	memset(ws, 0, sizeof(ws));



	/* We need to take out the map fd for the digest calculation

	 * since they are unstable from user space side.

	 */

	dst = (void *)raw;

	for (i = 0, was_ld_map = false; i < fp->len; i++) {

		dst[i] = fp->insnsi[i];

		if (!was_ld_map &&
@@ -177,12 +178,13 @@ void bpf_prog_calc_digest(struct bpf_prog *fp) 
		}

	}



	psize = fp->len * sizeof(struct bpf_insn);

	memset(&raw[psize], 0, sizeof(raw) - psize);

	psize = bpf_prog_insn_size(fp);

	memset(&raw[psize], 0, raw_size - psize);

	raw[psize++] = 0x80;



	bsize  = round_up(psize, SHA_MESSAGE_BYTES);

	blocks = bsize / SHA_MESSAGE_BYTES;

	todo   = raw;

	if (bsize - psize >= sizeof(__be64)) {

		bits = (__be64 *)(todo + bsize - sizeof(__be64));

	} else {
@@ -199,6 +201,9 @@ void bpf_prog_calc_digest(struct bpf_prog *fp) 
	result = (__force __be32 *)fp->digest;

	for (i = 0; i < SHA_DIGEST_WORDS; i++)

		result[i] = cpu_to_be32(fp->digest[i]);



	vfree(raw);

	return 0;

}



static bool bpf_is_jmp_and_has_target(const struct bpf_insn *insn)

kernel/bpf/syscall.c

+1 −1
Original line number Diff line number Diff line
@@ -811,7 +811,7 @@ static int bpf_prog_load(union bpf_attr *attr) 


	err = -EFAULT;

	if (copy_from_user(prog->insns, u64_to_user_ptr(attr->insns),

			   prog->len * sizeof(struct bpf_insn)) != 0)

			   bpf_prog_insn_size(prog)) != 0)

		goto free_prog;



	prog->orig_prog = NULL;

kernel/bpf/verifier.c

+4 −2
Original line number Diff line number Diff line
@@ -2931,6 +2931,10 @@ static int replace_map_fd_with_map_ptr(struct bpf_verifier_env *env) 
	int insn_cnt = env->prog->len;

	int i, j, err;



	err = bpf_prog_calc_digest(env->prog);

	if (err)

		return err;



	for (i = 0; i < insn_cnt; i++, insn++) {

		if (BPF_CLASS(insn->code) == BPF_LDX &&

		    (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
@@ -3178,8 +3182,6 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr) 
		log_level = 0;

	}



	bpf_prog_calc_digest(env->prog);



	ret = replace_map_fd_with_map_ptr(env);

	if (ret < 0)

		goto skip_full_check;