Commit 30f51aed authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
Browse files

libbpf: Cleanup temp FDs when intermediate sys_bpf fails. 



Fix loader program to close temporary FDs when intermediate
sys_bpf command fails.

Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-16-alexei.starovoitov@gmail.com
parent 67234743

tools/lib/bpf/bpf_gen_internal.h

+1 −0
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ struct bpf_gen { 
	void *data_cur;

	void *insn_start;

	void *insn_cur;

	ssize_t cleanup_label;

	__u32 nr_progs;

	__u32 nr_maps;

	int log_level;

tools/lib/bpf/gen_loader.c

+44 −4
Original line number Diff line number Diff line
@@ -101,8 +101,36 @@ static void emit2(struct bpf_gen *gen, struct bpf_insn insn1, struct bpf_insn in 


void bpf_gen__init(struct bpf_gen *gen, int log_level)

{

	size_t stack_sz = sizeof(struct loader_stack);

	int i;



	gen->log_level = log_level;

	/* save ctx pointer into R6 */

	emit(gen, BPF_MOV64_REG(BPF_REG_6, BPF_REG_1));



	/* bzero stack */

	emit(gen, BPF_MOV64_REG(BPF_REG_1, BPF_REG_10));

	emit(gen, BPF_ALU64_IMM(BPF_ADD, BPF_REG_1, -stack_sz));

	emit(gen, BPF_MOV64_IMM(BPF_REG_2, stack_sz));

	emit(gen, BPF_MOV64_IMM(BPF_REG_3, 0));

	emit(gen, BPF_EMIT_CALL(BPF_FUNC_probe_read_kernel));



	/* jump over cleanup code */

	emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0,

			      /* size of cleanup code below */

			      (stack_sz / 4) * 3 + 2));



	/* remember the label where all error branches will jump to */

	gen->cleanup_label = gen->insn_cur - gen->insn_start;

	/* emit cleanup code: close all temp FDs */

	for (i = 0; i < stack_sz; i += 4) {

		emit(gen, BPF_LDX_MEM(BPF_W, BPF_REG_1, BPF_REG_10, -stack_sz + i));

		emit(gen, BPF_JMP_IMM(BPF_JSLE, BPF_REG_1, 0, 1));

		emit(gen, BPF_EMIT_CALL(BPF_FUNC_sys_close));

	}

	/* R7 contains the error code from sys_bpf. Copy it into R0 and exit. */

	emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7));

	emit(gen, BPF_EXIT_INSN());

}



static int add_data(struct bpf_gen *gen, const void *data, __u32 size)
@@ -187,12 +215,24 @@ static void emit_sys_bpf(struct bpf_gen *gen, int cmd, int attr, int attr_size) 
	emit(gen, BPF_MOV64_REG(BPF_REG_7, BPF_REG_0));

}



static bool is_simm16(__s64 value)

{

	return value == (__s64)(__s16)value;

}



static void emit_check_err(struct bpf_gen *gen)

{

	emit(gen, BPF_JMP_IMM(BPF_JSGE, BPF_REG_7, 0, 2));

	emit(gen, BPF_MOV64_REG(BPF_REG_0, BPF_REG_7));

	/* TODO: close intermediate FDs in case of error */

	emit(gen, BPF_EXIT_INSN());

	__s64 off = -(gen->insn_cur - gen->insn_start - gen->cleanup_label) / 8 - 1;



	/* R7 contains result of last sys_bpf command.

	 * if (R7 < 0) goto cleanup;

	 */

	if (is_simm16(off)) {

		emit(gen, BPF_JMP_IMM(BPF_JSLT, BPF_REG_7, 0, off));

	} else {

		gen->error = -ERANGE;

		emit(gen, BPF_JMP_IMM(BPF_JA, 0, 0, -1));

	}

}



/* reg1 and reg2 should not be R1 - R5. They can be R0, R6 - R10 */