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    Subject[patch 23/86] kprobes: fix a memory leak in function pre_handler_kretprobe()
    3.2-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Jiang Liu <liuj97@gmail.com>

    commit 55ca6140e9bb307efc97a9301a4f501de02a6fd6 upstream.

    In function pre_handler_kretprobe(), the allocated kretprobe_instance
    object will get leaked if the entry_handler callback returns non-zero.
    This may cause all the preallocated kretprobe_instance objects exhausted.

    This issue can be reproduced by changing
    samples/kprobes/kretprobe_example.c to probe "mutex_unlock". And the fix
    is straightforward: just put the allocated kretprobe_instance object back
    onto the free_instances list.

    [akpm@linux-foundation.org: use raw_spin_lock/unlock]
    Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
    Acked-by: Jim Keniston <jkenisto@us.ibm.com>
    Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
    Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
    Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    kernel/kprobes.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    --- a/kernel/kprobes.c
    +++ b/kernel/kprobes.c
    @@ -1673,8 +1673,12 @@ static int __kprobes pre_handler_kretpro
    ri->rp = rp;
    ri->task = current;

    - if (rp->entry_handler && rp->entry_handler(ri, regs))
    + if (rp->entry_handler && rp->entry_handler(ri, regs)) {
    + raw_spin_lock_irqsave(&rp->lock, flags);
    + hlist_add_head(&ri->hlist, &rp->free_instances);
    + raw_spin_unlock_irqrestore(&rp->lock, flags);
    return 0;
    + }

    arch_prepare_kretprobe(ri, regs);




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