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libbpf: Cleanup temp FDs when intermediate sys_bpf fails.

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

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210514003623.28033-16-alexei.starovoitov@gmail.com
This commit is contained in:
Alexei Starovoitov 2021-05-13 17:36:17 -07:00 committed by Daniel Borkmann
parent 6723474373
commit 30f51aedab
2 changed files with 45 additions and 4 deletions
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1
tools/lib/bpf/bpf_gen_internal.h
View File

@ -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;

48
tools/lib/bpf/gen_loader.c
View File

@ -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 */