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    SubjectRe: [PATCH v3 1/2] kprobes: avoid the kprobe being re-registered
    On Fri, 27 Oct 2017 17:23:14 +0800
    Zhou Chengming <zhouchengming1@huawei.com> wrote:

    > Changes:
    > - We should put the modifies of the kprobe after the re-reg check.
    > - And then the address_safe check.
    >
    > Old code use check_kprobe_rereg() to check if the kprobe has been
    > registered already, but check_kprobe_rereg() will release the
    > kprobe_mutex then, so maybe two paths will pass the check and
    > register the same kprobe. This patch put the check inside the mutex.
    >
    > Suggested-by: Masami Hiramatsu <mhiramat@kernel.org>
    > Signed-off-by: Zhou Chengming <zhouchengming1@huawei.com>

    Looks good to me :)

    Acked-by: Masami Hiramatsu <mhiramat@kernel.org>

    Thanks!

    > ---
    > kernel/kprobes.c | 27 ++++++++-------------------
    > 1 file changed, 8 insertions(+), 19 deletions(-)
    >
    > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
    > index a1606a4..1eeedac 100644
    > --- a/kernel/kprobes.c
    > +++ b/kernel/kprobes.c
    > @@ -1443,19 +1443,6 @@ static struct kprobe *__get_valid_kprobe(struct kprobe *p)
    > return ap;
    > }
    >
    > -/* Return error if the kprobe is being re-registered */
    > -static inline int check_kprobe_rereg(struct kprobe *p)
    > -{
    > - int ret = 0;
    > -
    > - mutex_lock(&kprobe_mutex);
    > - if (__get_valid_kprobe(p))
    > - ret = -EINVAL;
    > - mutex_unlock(&kprobe_mutex);
    > -
    > - return ret;
    > -}
    > -
    > int __weak arch_check_ftrace_location(struct kprobe *p)
    > {
    > unsigned long ftrace_addr;
    > @@ -1536,9 +1523,13 @@ int register_kprobe(struct kprobe *p)
    > return PTR_ERR(addr);
    > p->addr = addr;
    >
    > - ret = check_kprobe_rereg(p);
    > - if (ret)
    > - return ret;
    > + mutex_lock(&kprobe_mutex);
    > +
    > + /* Return error if the kprobe is being re-registered */
    > + if (__get_valid_kprobe(p)) {
    > + ret = -EINVAL;
    > + goto out;
    > + }
    >
    > /* User can pass only KPROBE_FLAG_DISABLED to register_kprobe */
    > p->flags &= KPROBE_FLAG_DISABLED;
    > @@ -1547,9 +1538,7 @@ int register_kprobe(struct kprobe *p)
    >
    > ret = check_kprobe_address_safe(p, &probed_mod);
    > if (ret)
    > - return ret;
    > -
    > - mutex_lock(&kprobe_mutex);
    > + goto out;
    >
    > old_p = get_kprobe(p->addr);
    > if (old_p) {
    > --
    > 1.8.3.1
    >


    --
    Masami Hiramatsu <mhiramat@kernel.org>

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