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    SubjectRe: [PATCH v9 2/4] Uprobes/sdt: Prevent multiple reference counter for same uprobe
    On Sun, Aug 19, 2018 at 9:42 PM, Ravi Bangoria
    <ravi.bangoria@linux.ibm.com> wrote:
    > We assume to have only one reference counter for one uprobe.
    > Don't allow user to register multiple uprobes having same
    > inode+offset but different reference counter.
    >
    > Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
    > Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
    > Reviewed-by: Oleg Nesterov <oleg@redhat.com>

    Reviewed-by: Song Liu <songliubraving@fb.com>

    > ---
    > kernel/events/uprobes.c | 19 +++++++++++++++++++
    > 1 file changed, 19 insertions(+)
    >
    > diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
    > index 35065febcb6c..ecee371a59c7 100644
    > --- a/kernel/events/uprobes.c
    > +++ b/kernel/events/uprobes.c
    > @@ -679,6 +679,16 @@ static struct uprobe *insert_uprobe(struct uprobe *uprobe)
    > return u;
    > }
    >
    > +static void
    > +ref_ctr_mismatch_warn(struct uprobe *cur_uprobe, struct uprobe *uprobe)
    > +{
    > + pr_warn("ref_ctr_offset mismatch. inode: 0x%lx offset: 0x%llx "
    > + "ref_ctr_offset(old): 0x%llx ref_ctr_offset(new): 0x%llx\n",
    > + uprobe->inode->i_ino, (unsigned long long) uprobe->offset,
    > + (unsigned long long) cur_uprobe->ref_ctr_offset,
    > + (unsigned long long) uprobe->ref_ctr_offset);
    > +}
    > +
    > static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
    > loff_t ref_ctr_offset)
    > {
    > @@ -698,6 +708,12 @@ static struct uprobe *alloc_uprobe(struct inode *inode, loff_t offset,
    > cur_uprobe = insert_uprobe(uprobe);
    > /* a uprobe exists for this inode:offset combination */
    > if (cur_uprobe) {
    > + if (cur_uprobe->ref_ctr_offset != uprobe->ref_ctr_offset) {
    > + ref_ctr_mismatch_warn(cur_uprobe, uprobe);
    > + put_uprobe(cur_uprobe);
    > + kfree(uprobe);
    > + return ERR_PTR(-EINVAL);
    > + }
    > kfree(uprobe);
    > uprobe = cur_uprobe;
    > }
    > @@ -1112,6 +1128,9 @@ static int __uprobe_register(struct inode *inode, loff_t offset,
    > uprobe = alloc_uprobe(inode, offset, ref_ctr_offset);
    > if (!uprobe)
    > return -ENOMEM;
    > + if (IS_ERR(uprobe))
    > + return PTR_ERR(uprobe);
    > +
    > /*
    > * We can race with uprobe_unregister()->delete_uprobe().
    > * Check uprobe_is_active() and retry if it is false.
    > --
    > 2.14.4
    >

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