Messages in this thread | | | Date | Mon, 30 Oct 2017 09:10:57 +0800 | From | Bixuan Cui <> | Subject | Re: [PATCH] kernel/kprobes: add check to avoid memory leaks |
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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. > > 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 > > > > > . >
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