On Wed, 13 Jan 2021 17:48:45 -0500 Steven Rostedt <[email protected]> wrote:
> > Anything more on this? I need Wangshaobo's confirmation, because this is essentially a kind of programming bug, not a runtime bug. kprobes user must check the kprobe(kretprobe) must be unregistered and cleaned up before reusing it. (I recommend to re-alloc new data structure each time) For example, if you re-register your driver/filesystem without releasing, it will break the kernel. Thank you, > > -- Steve > > > On Tue, 22 Dec 2020 20:03:56 +0900 > Masami Hiramatsu <[email protected]> wrote: > > > On Mon, 21 Dec 2020 21:31:42 +0800 > > "Wangshaobo (bobo)" <[email protected]> wrote: > > > > > Hi steven, Masami, > > > We have encountered a problem, when we attempted to use steven's > > > suggestion as following, > > > > > > >>> If you call this here, you must make sure kprobe_addr() is called on > > > >>> rp->kp. > > > >>> But if kretprobe_blacklist_size == 0, kprobe_addr() is not called > > > >>> before > > > >>> this check. So it should be in between kprobe_on_func_entry() and > > > >>> kretprobe_blacklist_size check, like this > > > >>> > > > >>> if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, > > > >>> rp->kp.offset)) > > > >>> return -EINVAL; > > > >>> > > > >>> addr = kprobe_addr(&rp->kp); > > > >>> if (IS_ERR(addr)) > > > >>> return PTR_ERR(addr); > > > >>> rp->kp.addr = addr; > > > > > > //there exists no-atomic operation risk, we should not modify any > > > rp->kp's information, not all arch ensure atomic operation here. > > > > > > >>> > > > >>> ret = check_kprobe_rereg(&rp->kp); > > > >>> if (WARN_ON(ret)) > > > >>> return ret; > > > >>> > > > >>> if (kretprobe_blacklist_size) { > > > >>> for (i = 0; > > + ret = > > > >>> check_kprobe_rereg(&rp->kp); > > > > > > it returns failure from register_kprobe() end called by > > > register_kretprobe() when > > > we registered a kretprobe through .symbol_name at first time(through > > > .addr is OK), > > > kprobe_addr() called at the begaining of register_kprobe() will recheck > > > and > > > failed at following place because at this time we symbol_name is not NULL > > > and addr is also. > > > > Good catch! Yes, it will reject if both kp->addr and kp->symbol are set. > > > > > > > > static kprobe_opcode_t *_kprobe_addr(const char *symbol_name, > > > unsigned int offset) > > > { > > > if ((symbol_name && addr) || (!symbol_name && !addr)) //we > > > failed here > > > > > > > > > So we attempted to move this sentence rp->kp.addr = addr to > > > __get_valid_kprobe() like this to > > > avoid explict usage of rp->kp.addr = addr in register_kretprobe(). > > > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > > index dd5821f753e6..ea014779edfe 100644 > > > --- a/kernel/kprobes.c > > > +++ b/kernel/kprobes.c > > > @@ -1502,10 +1502,15 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe > > > *p) > > > static struct kprobe *__get_valid_kprobe(struct kprobe *p) > > > { > > > struct kprobe *ap, *list_p; > > > + void *addr; > > > > > > lockdep_assert_held(&kprobe_mutex); > > > > > > - ap = get_kprobe(p->addr); > > > + addr = kprobe_addr(p); > > > + if (IS_ERR(addr)) > > > + return NULL; > > > + > > > + ap = get_kprobe(addr); > > > if (unlikely(!ap)) > > > return NULL; > > > > > > But it also failed when we second time attempted to register a same > > > kretprobe, it is also > > > becasue symbol_name and addr is not NULL when we used > > > __get_valid_kprobe(). > > > > What the "second time" means? If you reuse the kretprobe (and kprobe) you > > must > > reset (cleanup) the kp->addr or kp->symbol_name. That is the initial state. > > I think the API should not allow users to enter inconsistent information. > > > > > > > > So it seems has no idea expect for modifying _kprobe_addr() like > > > following this, the reason is that > > > the patch 0bd476e6c671 ("kallsyms: unexport kallsyms_lookup_name() and > > > kallsyms_on_each_symbol()") > > > has telled us we'd better use symbol name to register but not address > > > anymore. > > > > > > -static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr, > > > - const char *symbol_name, unsigned int offset) > > > +static kprobe_opcode_t *_kprobe_addr(const char *symbol_name, > > > + unsigned int offset) > > > { > > > - if ((symbol_name && addr) || (!symbol_name && !addr)) > > > + kprobe_opcode_t *addr; > > > + if (!symbol_name) > > > goto invalid; > > > > No, there are cases that the user will set only kp->addr, but no > > kp->symbol_name. > > > > > > > > For us, this modification has not caused a big impact on other modules, > > > only expects a little > > > influence on bpf from calling trace_kprobe_on_func_entry(), it can not > > > use addr to fill in > > > rp.kp in struct trace_event_call anymore. > > > > > > So i want to know your views, and i will resend this patch soon. > > > > OK, I think it is simpler to check the rp->kp.addr && rp->kp.symbol_name > > because it is not allowed (it can lead inconsistent setting). > > > > How about this code? Is this work for you? > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index 41fdbb7953c6..73500be564be 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -2103,6 +2103,14 @@ int register_kretprobe(struct kretprobe *rp) > > int i; > > void *addr; > > > > + /* It is not allowed to specify addr and symbol_name at the same > > time */ > > + if (rp->kp.addr && rp->kp.symbol_name) > > + return -EINVAL; > > + > > + /* If only rp->kp.addr is specified, check reregistering kprobes */ > > + if (rp->kp.addr && check_kprobe_rereg(&rp->kp)) > > + return -EINVAL; > > + > > if (!kprobe_on_func_entry(rp->kp.addr, rp->kp.symbol_name, > > rp->kp.offset)) > > return -EINVAL; > > > > > > Thank you, > > > -- Masami Hiramatsu <[email protected]>
