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authorAlexei Starovoitov <ast@kernel.org>2021-02-09 19:36:29 -0800
committerDaniel Borkmann <daniel@iogearbox.net>2021-02-11 16:19:13 +0100
commitca06f55b90020cd97f4cc6d52db95436162e7dcf (patch)
tree8b26786ccefbcd4c87f9229ddc680f6feb4004a2 /arch/x86/net/bpf_jit_comp.c
parentf2dd3b39467411c53703125a111f45b3672c1771 (diff)
downloadlinux-ca06f55b90020cd97f4cc6d52db95436162e7dcf.tar.bz2
bpf: Add per-program recursion prevention mechanism
Since both sleepable and non-sleepable programs execute under migrate_disable add recursion prevention mechanism to both types of programs when they're executed via bpf trampoline. 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/20210210033634.62081-5-alexei.starovoitov@gmail.com
Diffstat (limited to 'arch/x86/net/bpf_jit_comp.c')
-rw-r--r--arch/x86/net/bpf_jit_comp.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index d11b9bcebbea..79e7a0ec1da5 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -1740,8 +1740,11 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
struct bpf_prog *p, int stack_size, bool mod_ret)
{
u8 *prog = *pprog;
+ u8 *jmp_insn;
int cnt = 0;
+ /* arg1: mov rdi, progs[i] */
+ emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32, (u32) (long) p);
if (emit_call(&prog,
p->aux->sleepable ? __bpf_prog_enter_sleepable :
__bpf_prog_enter, prog))
@@ -1749,6 +1752,14 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
/* remember prog start time returned by __bpf_prog_enter */
emit_mov_reg(&prog, true, BPF_REG_6, BPF_REG_0);
+ /* if (__bpf_prog_enter*(prog) == 0)
+ * goto skip_exec_of_prog;
+ */
+ EMIT3(0x48, 0x85, 0xC0); /* test rax,rax */
+ /* emit 2 nops that will be replaced with JE insn */
+ jmp_insn = prog;
+ emit_nops(&prog, 2);
+
/* arg1: lea rdi, [rbp - stack_size] */
EMIT4(0x48, 0x8D, 0x7D, -stack_size);
/* arg2: progs[i]->insnsi for interpreter */
@@ -1767,6 +1778,10 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
if (mod_ret)
emit_stx(&prog, BPF_DW, BPF_REG_FP, BPF_REG_0, -8);
+ /* replace 2 nops with JE insn, since jmp target is known */
+ jmp_insn[0] = X86_JE;
+ jmp_insn[1] = prog - jmp_insn - 2;
+
/* arg1: mov rdi, progs[i] */
emit_mov_imm64(&prog, BPF_REG_1, (long) p >> 32, (u32) (long) p);
/* arg2: mov rsi, rbx <- start time in nsec */