Message ID | 1509633431-2184-2-git-send-email-josef@toxicpanda.com |
---|---|
State | Changes Requested, archived |
Delegated to: | David Miller |
Headers | show |
Series | Add the ability to do BPF directed error injection | expand |
Hi Josef, one more issue I just noticed, see comment below: On 11/02/2017 03:37 PM, Josef Bacik wrote: [...] > diff --git a/include/linux/filter.h b/include/linux/filter.h > index cdd78a7beaae..dfa44fd74bae 100644 > --- a/include/linux/filter.h > +++ b/include/linux/filter.h > @@ -458,7 +458,8 @@ struct bpf_prog { > locked:1, /* Program image locked? */ > gpl_compatible:1, /* Is filter GPL compatible? */ > cb_access:1, /* Is control block accessed? */ > - dst_needed:1; /* Do we need dst entry? */ > + dst_needed:1, /* Do we need dst entry? */ > + kprobe_override:1; /* Do we override a kprobe? */ > kmemcheck_bitfield_end(meta); > enum bpf_prog_type type; /* Type of BPF program */ > u32 len; /* Number of filter blocks */ [...] > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > index d906775e12c1..f8f7927a9152 100644 > --- a/kernel/bpf/verifier.c > +++ b/kernel/bpf/verifier.c > @@ -4189,6 +4189,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > prog->dst_needed = 1; > if (insn->imm == BPF_FUNC_get_prandom_u32) > bpf_user_rnd_init_once(); > + if (insn->imm == BPF_FUNC_override_return) > + prog->kprobe_override = 1; > if (insn->imm == BPF_FUNC_tail_call) { > /* If we tail call into other programs, we > * cannot make any assumptions since they can > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 9660ee65fbef..0d7fce52391d 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -8169,6 +8169,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) > return -EINVAL; > } > > + /* Kprobe override only works for kprobes, not uprobes. */ > + if (prog->kprobe_override && > + !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) { > + bpf_prog_put(prog); > + return -EINVAL; > + } Can we somehow avoid the prog->kprobe_override flag here completely and also same in the perf_event_attach_bpf_prog() handler? Reason is that it's not reliable for bailing out this way: Think of the main program you're attaching doesn't use bpf_override_return() helper, but it tail-calls into other BPF progs that make use of it instead. So above check would be useless and will fail and we continue to attach the prog for probes where it's not intended to be used. We've had similar issues in the past e.g. c2002f983767 ("bpf: fix checking xdp_adjust_head on tail calls") is just one of those. Thus, can we avoid the flag altogether and handle such error case differently? > if (is_tracepoint || is_syscall_tp) { > int off = trace_event_get_offsets(event->tp_event); Thanks, Daniel
On Fri, Nov 03, 2017 at 12:12:13AM +0100, Daniel Borkmann wrote: > Hi Josef, > > one more issue I just noticed, see comment below: > > On 11/02/2017 03:37 PM, Josef Bacik wrote: > [...] > > diff --git a/include/linux/filter.h b/include/linux/filter.h > > index cdd78a7beaae..dfa44fd74bae 100644 > > --- a/include/linux/filter.h > > +++ b/include/linux/filter.h > > @@ -458,7 +458,8 @@ struct bpf_prog { > > locked:1, /* Program image locked? */ > > gpl_compatible:1, /* Is filter GPL compatible? */ > > cb_access:1, /* Is control block accessed? */ > > - dst_needed:1; /* Do we need dst entry? */ > > + dst_needed:1, /* Do we need dst entry? */ > > + kprobe_override:1; /* Do we override a kprobe? */ > > kmemcheck_bitfield_end(meta); > > enum bpf_prog_type type; /* Type of BPF program */ > > u32 len; /* Number of filter blocks */ > [...] > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > index d906775e12c1..f8f7927a9152 100644 > > --- a/kernel/bpf/verifier.c > > +++ b/kernel/bpf/verifier.c > > @@ -4189,6 +4189,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > > prog->dst_needed = 1; > > if (insn->imm == BPF_FUNC_get_prandom_u32) > > bpf_user_rnd_init_once(); > > + if (insn->imm == BPF_FUNC_override_return) > > + prog->kprobe_override = 1; > > if (insn->imm == BPF_FUNC_tail_call) { > > /* If we tail call into other programs, we > > * cannot make any assumptions since they can > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > index 9660ee65fbef..0d7fce52391d 100644 > > --- a/kernel/events/core.c > > +++ b/kernel/events/core.c > > @@ -8169,6 +8169,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) > > return -EINVAL; > > } > > > > + /* Kprobe override only works for kprobes, not uprobes. */ > > + if (prog->kprobe_override && > > + !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) { > > + bpf_prog_put(prog); > > + return -EINVAL; > > + } > > Can we somehow avoid the prog->kprobe_override flag here completely > and also same in the perf_event_attach_bpf_prog() handler? > > Reason is that it's not reliable for bailing out this way: Think of > the main program you're attaching doesn't use bpf_override_return() > helper, but it tail-calls into other BPF progs that make use of it > instead. So above check would be useless and will fail and we continue > to attach the prog for probes where it's not intended to be used. > > We've had similar issues in the past e.g. c2002f983767 ("bpf: fix > checking xdp_adjust_head on tail calls") is just one of those. Thus, > can we avoid the flag altogether and handle such error case differently? > So if I'm reading this right there's no way to know what we'll tail call at any given point, so I need to go back to my previous iteration of this patch and always save the state of the kprobe in the per-cpu variable to make sure we don't use bpf_override_return in the wrong case? The tail call functions won't be in the BPF_PROG_ARRAY right? It'll be just some other arbitrary function? If that's the case then we really need something like this https://patchwork.kernel.org/patch/10034815/ and I need to bring that back right? Thanks, Josef
On 11/03/2017 03:31 PM, Josef Bacik wrote: > On Fri, Nov 03, 2017 at 12:12:13AM +0100, Daniel Borkmann wrote: >> Hi Josef, >> >> one more issue I just noticed, see comment below: >> >> On 11/02/2017 03:37 PM, Josef Bacik wrote: >> [...] >>> diff --git a/include/linux/filter.h b/include/linux/filter.h >>> index cdd78a7beaae..dfa44fd74bae 100644 >>> --- a/include/linux/filter.h >>> +++ b/include/linux/filter.h >>> @@ -458,7 +458,8 @@ struct bpf_prog { >>> locked:1, /* Program image locked? */ >>> gpl_compatible:1, /* Is filter GPL compatible? */ >>> cb_access:1, /* Is control block accessed? */ >>> - dst_needed:1; /* Do we need dst entry? */ >>> + dst_needed:1, /* Do we need dst entry? */ >>> + kprobe_override:1; /* Do we override a kprobe? */ >>> kmemcheck_bitfield_end(meta); >>> enum bpf_prog_type type; /* Type of BPF program */ >>> u32 len; /* Number of filter blocks */ >> [...] >>> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c >>> index d906775e12c1..f8f7927a9152 100644 >>> --- a/kernel/bpf/verifier.c >>> +++ b/kernel/bpf/verifier.c >>> @@ -4189,6 +4189,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) >>> prog->dst_needed = 1; >>> if (insn->imm == BPF_FUNC_get_prandom_u32) >>> bpf_user_rnd_init_once(); >>> + if (insn->imm == BPF_FUNC_override_return) >>> + prog->kprobe_override = 1; >>> if (insn->imm == BPF_FUNC_tail_call) { >>> /* If we tail call into other programs, we >>> * cannot make any assumptions since they can >>> diff --git a/kernel/events/core.c b/kernel/events/core.c >>> index 9660ee65fbef..0d7fce52391d 100644 >>> --- a/kernel/events/core.c >>> +++ b/kernel/events/core.c >>> @@ -8169,6 +8169,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) >>> return -EINVAL; >>> } >>> >>> + /* Kprobe override only works for kprobes, not uprobes. */ >>> + if (prog->kprobe_override && >>> + !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) { >>> + bpf_prog_put(prog); >>> + return -EINVAL; >>> + } >> >> Can we somehow avoid the prog->kprobe_override flag here completely >> and also same in the perf_event_attach_bpf_prog() handler? >> >> Reason is that it's not reliable for bailing out this way: Think of >> the main program you're attaching doesn't use bpf_override_return() >> helper, but it tail-calls into other BPF progs that make use of it >> instead. So above check would be useless and will fail and we continue >> to attach the prog for probes where it's not intended to be used. >> >> We've had similar issues in the past e.g. c2002f983767 ("bpf: fix >> checking xdp_adjust_head on tail calls") is just one of those. Thus, >> can we avoid the flag altogether and handle such error case differently? > > So if I'm reading this right there's no way to know what we'll tail call at any > given point, so I need to go back to my previous iteration of this patch and > always save the state of the kprobe in the per-cpu variable to make sure we > don't use bpf_override_return in the wrong case? Yeah. > The tail call functions won't be in the BPF_PROG_ARRAY right? It'll be just > some other arbitrary function? If that's the case then we really need something > like this With BPF_PROG_ARRAY you mean BPF_MAP_TYPE_PROG_ARRAY or the prog array for the tracing/multiprog attach point? The program you're calling into is inside the BPF_MAP_TYPE_PROG_ARRAY map, but can change at any time and can have nesting as well. > https://patchwork.kernel.org/patch/10034815/ > > and I need to bring that back right? Thanks, I'm afraid so. The thing with skb cb_access which was brought up there is that once you have a tail call in the prog you cannot make any assumptions anymore, therefore the cb_access flag is set to 1 so we save/restore for those cases precautionary since it could be accessed or not later on. In your case I think this wouldn't work since legitimate bpf kprobes progs could use tail calls today, so setting prog->kprobe_override there would prevent attaching for non-kprobes due to subsequent flags & TRACE_EVENT_FL_KPROBE check.
On Fri, Nov 03, 2017 at 05:52:22PM +0100, Daniel Borkmann wrote: > On 11/03/2017 03:31 PM, Josef Bacik wrote: > > On Fri, Nov 03, 2017 at 12:12:13AM +0100, Daniel Borkmann wrote: > > > Hi Josef, > > > > > > one more issue I just noticed, see comment below: > > > > > > On 11/02/2017 03:37 PM, Josef Bacik wrote: > > > [...] > > > > diff --git a/include/linux/filter.h b/include/linux/filter.h > > > > index cdd78a7beaae..dfa44fd74bae 100644 > > > > --- a/include/linux/filter.h > > > > +++ b/include/linux/filter.h > > > > @@ -458,7 +458,8 @@ struct bpf_prog { > > > > locked:1, /* Program image locked? */ > > > > gpl_compatible:1, /* Is filter GPL compatible? */ > > > > cb_access:1, /* Is control block accessed? */ > > > > - dst_needed:1; /* Do we need dst entry? */ > > > > + dst_needed:1, /* Do we need dst entry? */ > > > > + kprobe_override:1; /* Do we override a kprobe? */ > > > > kmemcheck_bitfield_end(meta); > > > > enum bpf_prog_type type; /* Type of BPF program */ > > > > u32 len; /* Number of filter blocks */ > > > [...] > > > > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c > > > > index d906775e12c1..f8f7927a9152 100644 > > > > --- a/kernel/bpf/verifier.c > > > > +++ b/kernel/bpf/verifier.c > > > > @@ -4189,6 +4189,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) > > > > prog->dst_needed = 1; > > > > if (insn->imm == BPF_FUNC_get_prandom_u32) > > > > bpf_user_rnd_init_once(); > > > > + if (insn->imm == BPF_FUNC_override_return) > > > > + prog->kprobe_override = 1; > > > > if (insn->imm == BPF_FUNC_tail_call) { > > > > /* If we tail call into other programs, we > > > > * cannot make any assumptions since they can > > > > diff --git a/kernel/events/core.c b/kernel/events/core.c > > > > index 9660ee65fbef..0d7fce52391d 100644 > > > > --- a/kernel/events/core.c > > > > +++ b/kernel/events/core.c > > > > @@ -8169,6 +8169,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) > > > > return -EINVAL; > > > > } > > > > > > > > + /* Kprobe override only works for kprobes, not uprobes. */ > > > > + if (prog->kprobe_override && > > > > + !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) { > > > > + bpf_prog_put(prog); > > > > + return -EINVAL; > > > > + } > > > > > > Can we somehow avoid the prog->kprobe_override flag here completely > > > and also same in the perf_event_attach_bpf_prog() handler? > > > > > > Reason is that it's not reliable for bailing out this way: Think of > > > the main program you're attaching doesn't use bpf_override_return() > > > helper, but it tail-calls into other BPF progs that make use of it > > > instead. So above check would be useless and will fail and we continue > > > to attach the prog for probes where it's not intended to be used. > > > > > > We've had similar issues in the past e.g. c2002f983767 ("bpf: fix > > > checking xdp_adjust_head on tail calls") is just one of those. Thus, > > > can we avoid the flag altogether and handle such error case differently? > > > > So if I'm reading this right there's no way to know what we'll tail call at any > > given point, so I need to go back to my previous iteration of this patch and > > always save the state of the kprobe in the per-cpu variable to make sure we > > don't use bpf_override_return in the wrong case? > > Yeah. > > > The tail call functions won't be in the BPF_PROG_ARRAY right? It'll be just > > some other arbitrary function? If that's the case then we really need something > > like this > > With BPF_PROG_ARRAY you mean BPF_MAP_TYPE_PROG_ARRAY or the prog array > for the tracing/multiprog attach point? The program you're calling into > is inside the BPF_MAP_TYPE_PROG_ARRAY map, but can change at any time > and can have nesting as well. > > > https://patchwork.kernel.org/patch/10034815/ > > > > and I need to bring that back right? Thanks, > > I'm afraid so. The thing with skb cb_access which was brought up there is > that once you have a tail call in the prog you cannot make any assumptions > anymore, therefore the cb_access flag is set to 1 so we save/restore for > those cases precautionary since it could be accessed or not later on. In > your case I think this wouldn't work since legitimate bpf kprobes progs could > use tail calls today, so setting prog->kprobe_override there would prevent > attaching for non-kprobes due to subsequent flags & TRACE_EVENT_FL_KPROBE > check. how about preventing programs that use bpf_override_return to be store into prog_array? imo that would be cleaner solution. doing tail_call into them is kinda useless anyway. Then we can keep the bit and fast path.
diff --git a/arch/Kconfig b/arch/Kconfig index d789a89cb32c..4fb618082259 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -195,6 +195,9 @@ config HAVE_OPTPROBES config HAVE_KPROBES_ON_FTRACE bool +config HAVE_KPROBE_OVERRIDE + bool + config HAVE_NMI bool diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 971feac13506..5126d2750dd0 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -152,6 +152,7 @@ config X86 select HAVE_KERNEL_XZ select HAVE_KPROBES select HAVE_KPROBES_ON_FTRACE + select HAVE_KPROBE_OVERRIDE select HAVE_KRETPROBES select HAVE_KVM select HAVE_LIVEPATCH if X86_64 diff --git a/arch/x86/include/asm/kprobes.h b/arch/x86/include/asm/kprobes.h index 6cf65437b5e5..c6c3b1f4306a 100644 --- a/arch/x86/include/asm/kprobes.h +++ b/arch/x86/include/asm/kprobes.h @@ -67,6 +67,10 @@ extern const int kretprobe_blacklist_size; void arch_remove_kprobe(struct kprobe *p); asmlinkage void kretprobe_trampoline(void); +#ifdef CONFIG_KPROBES_ON_FTRACE +extern void arch_ftrace_kprobe_override_function(struct pt_regs *regs); +#endif + /* Architecture specific copy of original instruction*/ struct arch_specific_insn { /* copy of the original instruction */ diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 91c04c8e67fa..f04e71800c2f 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -108,6 +108,11 @@ static inline unsigned long regs_return_value(struct pt_regs *regs) return regs->ax; } +static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc) +{ + regs->ax = rc; +} + /* * user_mode(regs) determines whether a register set came from user * mode. On x86_32, this is true if V8086 mode was enabled OR if the diff --git a/arch/x86/kernel/kprobes/ftrace.c b/arch/x86/kernel/kprobes/ftrace.c index 041f7b6dfa0f..3c455bf490cb 100644 --- a/arch/x86/kernel/kprobes/ftrace.c +++ b/arch/x86/kernel/kprobes/ftrace.c @@ -97,3 +97,17 @@ int arch_prepare_kprobe_ftrace(struct kprobe *p) p->ainsn.boostable = false; return 0; } + +asmlinkage void override_func(void); +asm( + ".type override_func, @function\n" + "override_func:\n" + " ret\n" + ".size override_func, .-override_func\n" +); + +void arch_ftrace_kprobe_override_function(struct pt_regs *regs) +{ + regs->ip = (unsigned long)&override_func; +} +NOKPROBE_SYMBOL(arch_ftrace_kprobe_override_function); diff --git a/include/linux/filter.h b/include/linux/filter.h index cdd78a7beaae..dfa44fd74bae 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -458,7 +458,8 @@ struct bpf_prog { locked:1, /* Program image locked? */ gpl_compatible:1, /* Is filter GPL compatible? */ cb_access:1, /* Is control block accessed? */ - dst_needed:1; /* Do we need dst entry? */ + dst_needed:1, /* Do we need dst entry? */ + kprobe_override:1; /* Do we override a kprobe? */ kmemcheck_bitfield_end(meta); enum bpf_prog_type type; /* Type of BPF program */ u32 len; /* Number of filter blocks */ diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h index fc6aeca945db..be8bd5a8efaa 100644 --- a/include/linux/trace_events.h +++ b/include/linux/trace_events.h @@ -522,6 +522,7 @@ do { \ struct perf_event; DECLARE_PER_CPU(struct pt_regs, perf_trace_regs); +DECLARE_PER_CPU(int, bpf_kprobe_override); extern int perf_trace_init(struct perf_event *event); extern void perf_trace_destroy(struct perf_event *event); diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 0b7b54d898bd..1ad5b87a42f6 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -673,6 +673,10 @@ union bpf_attr { * @buf: buf to fill * @buf_size: size of the buf * Return : 0 on success or negative error code + * + * int bpf_override_return(pt_regs, rc) + * @pt_regs: pointer to struct pt_regs + * @rc: the return value to set */ #define __BPF_FUNC_MAPPER(FN) \ FN(unspec), \ @@ -732,7 +736,8 @@ union bpf_attr { FN(xdp_adjust_meta), \ FN(perf_event_read_value), \ FN(perf_prog_read_value), \ - FN(getsockopt), + FN(getsockopt), \ + FN(override_return), /* integer value in 'imm' field of BPF_CALL instruction selects which helper * function eBPF program intends to call diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index d906775e12c1..f8f7927a9152 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -4189,6 +4189,8 @@ static int fixup_bpf_calls(struct bpf_verifier_env *env) prog->dst_needed = 1; if (insn->imm == BPF_FUNC_get_prandom_u32) bpf_user_rnd_init_once(); + if (insn->imm == BPF_FUNC_override_return) + prog->kprobe_override = 1; if (insn->imm == BPF_FUNC_tail_call) { /* If we tail call into other programs, we * cannot make any assumptions since they can diff --git a/kernel/events/core.c b/kernel/events/core.c index 9660ee65fbef..0d7fce52391d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8169,6 +8169,13 @@ static int perf_event_set_bpf_prog(struct perf_event *event, u32 prog_fd) return -EINVAL; } + /* Kprobe override only works for kprobes, not uprobes. */ + if (prog->kprobe_override && + !(event->tp_event->flags & TRACE_EVENT_FL_KPROBE)) { + bpf_prog_put(prog); + return -EINVAL; + } + if (is_tracepoint || is_syscall_tp) { int off = trace_event_get_offsets(event->tp_event); diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig index 434c840e2d82..9dc0deeaad2b 100644 --- a/kernel/trace/Kconfig +++ b/kernel/trace/Kconfig @@ -518,6 +518,17 @@ config FUNCTION_PROFILER If in doubt, say N. +config BPF_KPROBE_OVERRIDE + bool "Enable BPF programs to override a kprobed function" + depends on BPF_EVENTS + depends on KPROBES_ON_FTRACE + depends on HAVE_KPROBE_OVERRIDE + depends on DYNAMIC_FTRACE_WITH_REGS + default n + help + Allows BPF to override the execution of a probed function and + set a different return value. This is used for error injection. + config FTRACE_MCOUNT_RECORD def_bool y depends on DYNAMIC_FTRACE diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 136aa6bb0422..26be195a4e39 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -13,6 +13,10 @@ #include <linux/filter.h> #include <linux/uaccess.h> #include <linux/ctype.h> +#include <linux/kprobes.h> +#include <asm/kprobes.h> + +#include "trace_probe.h" #include "trace.h" u64 bpf_get_stackid(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5); @@ -76,6 +80,29 @@ unsigned int trace_call_bpf(struct trace_event_call *call, void *ctx) } EXPORT_SYMBOL_GPL(trace_call_bpf); +#ifdef CONFIG_BPF_KPROBE_OVERRIDE +BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc) +{ + __this_cpu_write(bpf_kprobe_override, 1); + regs_set_return_value(regs, rc); + arch_ftrace_kprobe_override_function(regs); + return 0; +} +#else +BPF_CALL_2(bpf_override_return, struct pt_regs *, regs, unsigned long, rc) +{ + return -EINVAL; +} +#endif + +static const struct bpf_func_proto bpf_override_return_proto = { + .func = bpf_override_return, + .gpl_only = true, + .ret_type = RET_INTEGER, + .arg1_type = ARG_PTR_TO_CTX, + .arg2_type = ARG_ANYTHING, +}; + BPF_CALL_3(bpf_probe_read, void *, dst, u32, size, const void *, unsafe_ptr) { int ret; @@ -551,6 +578,10 @@ static const struct bpf_func_proto *kprobe_prog_func_proto(enum bpf_func_id func return &bpf_get_stackid_proto; case BPF_FUNC_perf_event_read_value: return &bpf_perf_event_read_value_proto; + case BPF_FUNC_override_return: + pr_warn_ratelimited("%s[%d] is installing a program with bpf_override_return helper that may cause unexpected behavior!", + current->comm, task_pid_nr(current)); + return &bpf_override_return_proto; default: return tracing_func_proto(func_id); } @@ -766,6 +797,10 @@ int perf_event_attach_bpf_prog(struct perf_event *event, struct bpf_prog_array *new_array; int ret = -EEXIST; + /* Kprobe override only works for ftrace based kprobes. */ + if (prog->kprobe_override && !trace_kprobe_ftrace(event->tp_event)) + return -EINVAL; + mutex_lock(&bpf_event_mutex); if (event->prog) diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c index abf92e478cfb..8e3c9ec1faf7 100644 --- a/kernel/trace/trace_kprobe.c +++ b/kernel/trace/trace_kprobe.c @@ -42,6 +42,7 @@ struct trace_kprobe { (offsetof(struct trace_kprobe, tp.args) + \ (sizeof(struct probe_arg) * (n))) +DEFINE_PER_CPU(int, bpf_kprobe_override); static nokprobe_inline bool trace_kprobe_is_return(struct trace_kprobe *tk) { @@ -87,6 +88,12 @@ static nokprobe_inline unsigned long trace_kprobe_nhit(struct trace_kprobe *tk) return nhit; } +int trace_kprobe_ftrace(struct trace_event_call *call) +{ + struct trace_kprobe *tk = (struct trace_kprobe *)call->data; + return kprobe_ftrace(&tk->rp.kp); +} + static int register_kprobe_event(struct trace_kprobe *tk); static int unregister_kprobe_event(struct trace_kprobe *tk); @@ -1170,7 +1177,7 @@ static int kretprobe_event_define_fields(struct trace_event_call *event_call) #ifdef CONFIG_PERF_EVENTS /* Kprobe profile handler */ -static void +static int kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) { struct trace_event_call *call = &tk->tp.call; @@ -1179,12 +1186,29 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) int size, __size, dsize; int rctx; - if (bpf_prog_array_valid(call) && !trace_call_bpf(call, regs)) - return; + if (bpf_prog_array_valid(call)) { + int ret; + + ret = trace_call_bpf(call, regs); + + /* + * We need to check and see if we modified the pc of the + * pt_regs, and if so clear the kprobe and return 1 so that we + * don't do the instruction skipping. Also reset our state so + * we are clean the next pass through. + */ + if (__this_cpu_read(bpf_kprobe_override)) { + __this_cpu_write(bpf_kprobe_override, 0); + reset_current_kprobe(); + return 1; + } + if (!ret) + return 0; + } head = this_cpu_ptr(call->perf_events); if (hlist_empty(head)) - return; + return 0; dsize = __get_data_size(&tk->tp, regs); __size = sizeof(*entry) + tk->tp.size + dsize; @@ -1193,13 +1217,14 @@ kprobe_perf_func(struct trace_kprobe *tk, struct pt_regs *regs) entry = perf_trace_buf_alloc(size, NULL, &rctx); if (!entry) - return; + return 0; entry->ip = (unsigned long)tk->rp.kp.addr; memset(&entry[1], 0, dsize); store_trace_args(sizeof(*entry), &tk->tp, regs, (u8 *)&entry[1], dsize); perf_trace_buf_submit(entry, size, rctx, call->event.type, 1, regs, head, NULL, NULL); + return 0; } NOKPROBE_SYMBOL(kprobe_perf_func); @@ -1275,6 +1300,7 @@ static int kprobe_register(struct trace_event_call *event, static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs) { struct trace_kprobe *tk = container_of(kp, struct trace_kprobe, rp.kp); + int ret = 0; raw_cpu_inc(*tk->nhit); @@ -1282,9 +1308,9 @@ static int kprobe_dispatcher(struct kprobe *kp, struct pt_regs *regs) kprobe_trace_func(tk, regs); #ifdef CONFIG_PERF_EVENTS if (tk->tp.flags & TP_FLAG_PROFILE) - kprobe_perf_func(tk, regs); + ret = kprobe_perf_func(tk, regs); #endif - return 0; /* We don't tweek kernel, so just return 0 */ + return ret; } NOKPROBE_SYMBOL(kprobe_dispatcher); diff --git a/kernel/trace/trace_probe.h b/kernel/trace/trace_probe.h index 903273c93e61..adbb3f7d1fb5 100644 --- a/kernel/trace/trace_probe.h +++ b/kernel/trace/trace_probe.h @@ -253,6 +253,7 @@ struct symbol_cache; unsigned long update_symbol_cache(struct symbol_cache *sc); void free_symbol_cache(struct symbol_cache *sc); struct symbol_cache *alloc_symbol_cache(const char *sym, long offset); +int trace_kprobe_ftrace(struct trace_event_call *call); #else /* uprobes do not support symbol fetch methods */ #define fetch_symbol_u8 NULL @@ -278,6 +279,11 @@ alloc_symbol_cache(const char *sym, long offset) { return NULL; } + +static inline int trace_kprobe_ftrace(struct trace_event_call *call) +{ + return 0; +} #endif /* CONFIG_KPROBE_EVENTS */ struct probe_arg {