| Message ID | 20230215115430.236046-4-yangjihong1@huawei.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | kprobes: Fix issues related to optkprobe | expand |
On Wed, 15 Feb 2023 19:54:30 +0800 Yang Jihong <yangjihong1@huawei.com> wrote: > When arch_prepare_optimized_kprobe calculating jump destination address, > it copies original instructions from jmp-optimized kprobe (see > __recover_optprobed_insn), and calculated based on length of original > instruction. > > arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when > checking whether jmp-optimized kprobe exists. > As a result, setup_detour_execution may jump to a range that has been > overwritten by jump destination address, resulting in an inval opcode error. OK, good catch !! I missed "delayed unoptimization" case here too. > > For example, assume that register two kprobes whose addresses are > <func+9> and <func+11> in "func" function. > The original code of "func" function is as follows: > > 0xffffffff816cb5e9 <+9>: push %r12 > 0xffffffff816cb5eb <+11>: xor %r12d,%r12d > 0xffffffff816cb5ee <+14>: test %rdi,%rdi > 0xffffffff816cb5f1 <+17>: setne %r12b > 0xffffffff816cb5f5 <+21>: push %rbp > > 1.Register the kprobe for <func+11>, assume that is kp1, corresponding optimized_kprobe is op1. > After the optimization, "func" code changes to: > > 0xffffffff816cc079 <+9>: push %r12 > 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 > 0xffffffff816cc080 <+16>: incl 0xf(%rcx) > 0xffffffff816cc083 <+19>: xchg %eax,%ebp > 0xffffffff816cc084 <+20>: (bad) > 0xffffffff816cc085 <+21>: push %rbp > > Now op1->flags == KPROBE_FLAG_OPTIMATED; > > 2. Register the kprobe for <func+9>, assume that is kp2, corresponding optimized_kprobe is op2. > > register_kprobe(kp2) > register_aggr_kprobe > alloc_aggr_kprobe > __prepare_optimized_kprobe > arch_prepare_optimized_kprobe > __recover_optprobed_insn // copy original bytes from kp1->optinsn.copied_insn, > // jump address = <func+14> > > 3. disable kp1: > > disable_kprobe(kp1) > __disable_kprobe > ... > if (p == orig_p || aggr_kprobe_disabled(orig_p)) { > ret = disarm_kprobe(orig_p, true) // add op1 in unoptimizing_list, not unoptimized > orig_p->flags |= KPROBE_FLAG_DISABLED; // op1->flags == KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED > ... > > 4. unregister kp2 > __unregister_kprobe_top > ... > if (!kprobe_disabled(ap) && !kprobes_all_disarmed) { > optimize_kprobe(op) > ... > if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return > return; > p->kp.flags |= KPROBE_FLAG_OPTIMIZED; // now op2 has KPROBE_FLAG_OPTIMIZED > } > > "func" code now is: > > 0xffffffff816cc079 <+9>: int3 > 0xffffffff816cc07a <+10>: push %rsp > 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 > 0xffffffff816cc080 <+16>: incl 0xf(%rcx) > 0xffffffff816cc083 <+19>: xchg %eax,%ebp > 0xffffffff816cc084 <+20>: (bad) > 0xffffffff816cc085 <+21>: push %rbp > > 5. if call "func", int3 handler call setup_detour_execution: > > if (p->flags & KPROBE_FLAG_OPTIMIZED) { > ... > regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; > ... > } > > The code for the destination address is > > 0xffffffffa021072c: push %r12 > 0xffffffffa021072e: xor %r12d,%r12d > 0xffffffffa0210731: jmp 0xffffffff816cb5ee <func+14> > > However, <func+14> is not a valid start instruction address. As a result, an error occurs. OK, it has been introduced by the same commit as previous one. (delayed unoptimization) > > Signed-off-by: Yang Jihong <yangjihong1@huawei.com> > --- > arch/x86/kernel/kprobes/opt.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c > index 3718d6863555..e6d9bd038401 100644 > --- a/arch/x86/kernel/kprobes/opt.c > +++ b/arch/x86/kernel/kprobes/opt.c > @@ -353,7 +353,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe *op) > > for (i = 1; i < op->optinsn.size; i++) { > p = get_kprobe(op->kp.addr + i); > - if (p && !kprobe_disabled(p)) > + if (p && (!kprobe_disabled(p) || kprobe_optimized(p))) Hmm, can you rewrite this with kprobe_disarmed() instead of kprobe_disabled()? Since this is checking there are any other kprobes are "armed" on the address where it will be replaced by jump. So it is natural to use "disarmed" check. Thank you, > return -EEXIST; > } > > -- > 2.30.GIT >
Hello Masami, On 2023/2/15 23:48, Masami Hiramatsu (Google) wrote: > On Wed, 15 Feb 2023 19:54:30 +0800 > Yang Jihong <yangjihong1@huawei.com> wrote: > >> When arch_prepare_optimized_kprobe calculating jump destination address, >> it copies original instructions from jmp-optimized kprobe (see >> __recover_optprobed_insn), and calculated based on length of original >> instruction. >> >> arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when >> checking whether jmp-optimized kprobe exists. >> As a result, setup_detour_execution may jump to a range that has been >> overwritten by jump destination address, resulting in an inval opcode error. > > OK, good catch !! I missed "delayed unoptimization" case here too. > >> >> For example, assume that register two kprobes whose addresses are >> <func+9> and <func+11> in "func" function. >> The original code of "func" function is as follows: >> >> 0xffffffff816cb5e9 <+9>: push %r12 >> 0xffffffff816cb5eb <+11>: xor %r12d,%r12d >> 0xffffffff816cb5ee <+14>: test %rdi,%rdi >> 0xffffffff816cb5f1 <+17>: setne %r12b >> 0xffffffff816cb5f5 <+21>: push %rbp >> >> 1.Register the kprobe for <func+11>, assume that is kp1, corresponding optimized_kprobe is op1. >> After the optimization, "func" code changes to: >> >> 0xffffffff816cc079 <+9>: push %r12 >> 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 >> 0xffffffff816cc080 <+16>: incl 0xf(%rcx) >> 0xffffffff816cc083 <+19>: xchg %eax,%ebp >> 0xffffffff816cc084 <+20>: (bad) >> 0xffffffff816cc085 <+21>: push %rbp >> >> Now op1->flags == KPROBE_FLAG_OPTIMATED; >> >> 2. Register the kprobe for <func+9>, assume that is kp2, corresponding optimized_kprobe is op2. >> >> register_kprobe(kp2) >> register_aggr_kprobe >> alloc_aggr_kprobe >> __prepare_optimized_kprobe >> arch_prepare_optimized_kprobe >> __recover_optprobed_insn // copy original bytes from kp1->optinsn.copied_insn, >> // jump address = <func+14> >> >> 3. disable kp1: >> >> disable_kprobe(kp1) >> __disable_kprobe >> ... >> if (p == orig_p || aggr_kprobe_disabled(orig_p)) { >> ret = disarm_kprobe(orig_p, true) // add op1 in unoptimizing_list, not unoptimized >> orig_p->flags |= KPROBE_FLAG_DISABLED; // op1->flags == KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED >> ... >> >> 4. unregister kp2 >> __unregister_kprobe_top >> ... >> if (!kprobe_disabled(ap) && !kprobes_all_disarmed) { >> optimize_kprobe(op) >> ... >> if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return >> return; >> p->kp.flags |= KPROBE_FLAG_OPTIMIZED; // now op2 has KPROBE_FLAG_OPTIMIZED >> } >> >> "func" code now is: >> >> 0xffffffff816cc079 <+9>: int3 >> 0xffffffff816cc07a <+10>: push %rsp >> 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 >> 0xffffffff816cc080 <+16>: incl 0xf(%rcx) >> 0xffffffff816cc083 <+19>: xchg %eax,%ebp >> 0xffffffff816cc084 <+20>: (bad) >> 0xffffffff816cc085 <+21>: push %rbp >> >> 5. if call "func", int3 handler call setup_detour_execution: >> >> if (p->flags & KPROBE_FLAG_OPTIMIZED) { >> ... >> regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; >> ... >> } >> >> The code for the destination address is >> >> 0xffffffffa021072c: push %r12 >> 0xffffffffa021072e: xor %r12d,%r12d >> 0xffffffffa0210731: jmp 0xffffffff816cb5ee <func+14> >> >> However, <func+14> is not a valid start instruction address. As a result, an error occurs. > > OK, it has been introduced by the same commit as previous one. (delayed unoptimization) > OK, will add "Fixes: f66c0447cca1 ("kprobes: Set unoptimized flag after unoptimizing code")" in next version In addition, " Cc: stable@vger.kernel.org" is required, same as the previous patch. >> >> Signed-off-by: Yang Jihong <yangjihong1@huawei.com> >> --- >> arch/x86/kernel/kprobes/opt.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c >> index 3718d6863555..e6d9bd038401 100644 >> --- a/arch/x86/kernel/kprobes/opt.c >> +++ b/arch/x86/kernel/kprobes/opt.c >> @@ -353,7 +353,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe *op) >> >> for (i = 1; i < op->optinsn.size; i++) { >> p = get_kprobe(op->kp.addr + i); >> - if (p && !kprobe_disabled(p)) >> + if (p && (!kprobe_disabled(p) || kprobe_optimized(p))) > > Hmm, can you rewrite this with kprobe_disarmed() instead of kprobe_disabled()? > Since this is checking there are any other kprobes are "armed" on the address > where it will be replaced by jump. So it is natural to use "disarmed" check. > Yes, It is better to change it to use "kprobe_disarmed", will modify in next version. Thanks, Yang
diff --git a/arch/x86/kernel/kprobes/opt.c b/arch/x86/kernel/kprobes/opt.c index 3718d6863555..e6d9bd038401 100644 --- a/arch/x86/kernel/kprobes/opt.c +++ b/arch/x86/kernel/kprobes/opt.c @@ -353,7 +353,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe *op) for (i = 1; i < op->optinsn.size; i++) { p = get_kprobe(op->kp.addr + i); - if (p && !kprobe_disabled(p)) + if (p && (!kprobe_disabled(p) || kprobe_optimized(p))) return -EEXIST; }
When arch_prepare_optimized_kprobe calculating jump destination address, it copies original instructions from jmp-optimized kprobe (see __recover_optprobed_insn), and calculated based on length of original instruction. arch_check_optimized_kprobe does not check KPROBE_FLAG_OPTIMATED when checking whether jmp-optimized kprobe exists. As a result, setup_detour_execution may jump to a range that has been overwritten by jump destination address, resulting in an inval opcode error. For example, assume that register two kprobes whose addresses are <func+9> and <func+11> in "func" function. The original code of "func" function is as follows: 0xffffffff816cb5e9 <+9>: push %r12 0xffffffff816cb5eb <+11>: xor %r12d,%r12d 0xffffffff816cb5ee <+14>: test %rdi,%rdi 0xffffffff816cb5f1 <+17>: setne %r12b 0xffffffff816cb5f5 <+21>: push %rbp 1.Register the kprobe for <func+11>, assume that is kp1, corresponding optimized_kprobe is op1. After the optimization, "func" code changes to: 0xffffffff816cc079 <+9>: push %r12 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 0xffffffff816cc080 <+16>: incl 0xf(%rcx) 0xffffffff816cc083 <+19>: xchg %eax,%ebp 0xffffffff816cc084 <+20>: (bad) 0xffffffff816cc085 <+21>: push %rbp Now op1->flags == KPROBE_FLAG_OPTIMATED; 2. Register the kprobe for <func+9>, assume that is kp2, corresponding optimized_kprobe is op2. register_kprobe(kp2) register_aggr_kprobe alloc_aggr_kprobe __prepare_optimized_kprobe arch_prepare_optimized_kprobe __recover_optprobed_insn // copy original bytes from kp1->optinsn.copied_insn, // jump address = <func+14> 3. disable kp1: disable_kprobe(kp1) __disable_kprobe ... if (p == orig_p || aggr_kprobe_disabled(orig_p)) { ret = disarm_kprobe(orig_p, true) // add op1 in unoptimizing_list, not unoptimized orig_p->flags |= KPROBE_FLAG_DISABLED; // op1->flags == KPROBE_FLAG_OPTIMATED | KPROBE_FLAG_DISABLED ... 4. unregister kp2 __unregister_kprobe_top ... if (!kprobe_disabled(ap) && !kprobes_all_disarmed) { optimize_kprobe(op) ... if (arch_check_optimized_kprobe(op) < 0) // because op1 has KPROBE_FLAG_DISABLED, here not return return; p->kp.flags |= KPROBE_FLAG_OPTIMIZED; // now op2 has KPROBE_FLAG_OPTIMIZED } "func" code now is: 0xffffffff816cc079 <+9>: int3 0xffffffff816cc07a <+10>: push %rsp 0xffffffff816cc07b <+11>: jmp 0xffffffffa0210000 0xffffffff816cc080 <+16>: incl 0xf(%rcx) 0xffffffff816cc083 <+19>: xchg %eax,%ebp 0xffffffff816cc084 <+20>: (bad) 0xffffffff816cc085 <+21>: push %rbp 5. if call "func", int3 handler call setup_detour_execution: if (p->flags & KPROBE_FLAG_OPTIMIZED) { ... regs->ip = (unsigned long)op->optinsn.insn + TMPL_END_IDX; ... } The code for the destination address is 0xffffffffa021072c: push %r12 0xffffffffa021072e: xor %r12d,%r12d 0xffffffffa0210731: jmp 0xffffffff816cb5ee <func+14> However, <func+14> is not a valid start instruction address. As a result, an error occurs. Signed-off-by: Yang Jihong <yangjihong1@huawei.com> --- arch/x86/kernel/kprobes/opt.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)