Messages in this thread | ![/](/images/icornerl.gif) | | Date | Mon, 30 Oct 2017 13:42:21 +0900 | From | Masami Hiramatsu <> | Subject | Re: [PATCH] kernel/kprobes: add check to avoid memory leaks |
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On Mon, 30 Oct 2017 09:10:57 +0800 Bixuan Cui <cuibixuan@huawei.com> wrote:
> On 2017/10/25 20:29, Bixuan Cui wrote: > And test again with this patch: > > insmod testRegKretprobes_004.ko > [ 163.853281] register_kretprobe failed, returned -22 > insmod: can't insert 'testRegKretprobes_004.ko': Operation not permitted > > Thanks, > Bixuan Cui > > The register_kretprobe(struct kretprobe *rp) creates and initializes > > a hash list for rp->free_instances when register kretprobe every time. > > Then malloc memory for it. > > > > The test case: > > static struct kretprobe rp; > > struct kretprobe *rps[2]={&rp, &rp}; > > static int ret_handler(struct kretprobe_instance *ri, struct pt_regs *regs) > > { > > printk(KERN_DEBUG "ret_handler\n"); > > return 0; > > } > > static int entry_handler(struct kretprobe_instance *ri, struct pt_regs *regs) > > { > > printk(KERN_DEBUG "entry_handler\n"); > > return 0; > > } > > static int __init kretprobe_init(void) > > { > > int ret; > > rp.kp.addr = (kprobe_opcode_t *)kallsyms_lookup_name("do_fork"); > > rp.handler=ret_handler; > > rp.entry_handler=entry_handler; > > rp.maxactive = 3; > > > > ret = register_kretprobes(rps,2); > > > > Result: > > unreferenced object 0xffff8010b12ad980 (size 64): > > comm "insmod", pid 17352, jiffies 4298977824 (age 63065.756s) > > hex dump (first 32 bytes): > > 00 00 00 00 00 00 00 00 d8 84 12 fc ff 7f ff ff ................ > > 74 65 73 74 52 65 67 4b 72 65 74 70 72 6f 62 65 testRegKretprobe > > backtrace: > > [<ffff8000002cd880>] create_object+0x1e0/0x3f0 > > [<ffff800000fa3d6c>] kmemleak_alloc+0x6c/0xf0 > > [<ffff8000002ac97c>] __kmalloc+0x23c/0x2e0 > > [<ffff8000001a6f2c>] register_kretprobe+0x12c/0x350 > > > > When call register_kretprobes(struct kretprobe **rps, int num) with the > > same rps(num>=2). > > The first time,call INIT_HLIST_HEAD() and kmalloc() to malloc memory for the > > hash list,then save into rp->free_instances. > > The second time,call INIT_HLIST_HEAD() and kmalloc() then create a new > > hash list into rp->free_instances and lost the first rp->free_instances. > > So add check to avoid it. > >
I don't like this kind of check, since this is obviously caller's bug. Why doesn't each caller check this?
Thank you,
> > Reported-and-tested-by: kangwen <kangwen1@huawei.com> > > Signed-off-by: Bixuan Cui <cuibixuan@huawei.com> > > --- > > kernel/kprobes.c | 8 +++++++- > > 1 file changed, 7 insertions(+), 1 deletion(-) > > > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > > index 6301dae..f19f191 100644 > > --- a/kernel/kprobes.c > > +++ b/kernel/kprobes.c > > @@ -1890,10 +1890,16 @@ EXPORT_SYMBOL_GPL(register_kretprobe); > > > > int register_kretprobes(struct kretprobe **rps, int num) > > { > > - int ret = 0, i; > > + int ret = 0, i, j; > > > > if (num <= 0) > > return -EINVAL; > > + > > + for (i = 0; i < num-1; i++) > > + for (j = i+1; j < num; j++) > > + if (rps[i] == rps[j]) > > + return -EINVAL; > > + > > for (i = 0; i < num; i++) { > > ret = register_kretprobe(rps[i]); > > if (ret < 0) { > > -- > > 2.6.2 > > > > > > > > > > . > > > >
-- Masami Hiramatsu <mhiramat@kernel.org>
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