Messages in this thread Patch in this message |  | | Date | Wed, 25 Oct 2017 20:29:12 +0800 | | From | Bixuan Cui <> | | Subject | [PATCH] kernel/kprobes: add check to avoid memory leaks |
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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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