Messages in this thread | | | Date | Tue, 7 Feb 2017 09:03:43 +0100 | From | Michal Hocko <> | Subject | Re: kmemleak splat on copy_process() |
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On Tue 07-02-17 02:37:02, Luis R. Rodriguez wrote: > On Mon, Feb 06, 2017 at 10:47:41AM +0100, Michal Hocko wrote: > > On Fri 03-02-17 13:06:04, Luis R. Rodriguez wrote: > > > On next-20170125 running some kselftest not yet upstream I eventually > > > get a kmemleak splat: > > > > > > unreferenced object 0xffffa7b1034b4000 (size 16384): > > > comm "driver_data.sh", pid 6506, jiffies 4295068366 (age 1697.272s) > > > hex dump (first 32 bytes): > > > 9d 6e ac 57 00 00 00 00 74 2d 64 72 69 76 65 72 .n.W....t-driver > > > 5f 64 61 74 61 2e 62 69 6e 0a 00 00 00 00 00 00 _data.bin....... > > > backtrace: > > > [<ffffffff9005f7fa>] kmemleak_alloc+0x4a/0xa0 > > > [<ffffffff8fbe7006>] __vmalloc_node_range+0x206/0x2a0 > > > [<ffffffff8fa7f3e9>] copy_process.part.36+0x609/0x1cc0 > > > [<ffffffff8fa80c77>] _do_fork+0xd7/0x390 > > > [<ffffffff8fa80fd9>] SyS_clone+0x19/0x20 > > > [<ffffffff8fa03b4b>] do_syscall_64+0x5b/0xc0 > > > [<ffffffff9006b3af>] return_from_SYSCALL_64+0x0/0x6a > > > [<ffffffffffffffff>] 0xffffffffffffffff > > > > > > As per gdb: > > > > > > (gdb) l *(copy_process+0x609) > > > 0xffffffff8107f3e9 is in copy_process (kernel/fork.c:204). > > > warning: Source file is more recent than executable. > > > 199 /* > > > 200 * We can't call find_vm_area() in interrupt context, and > > > 201 * free_thread_stack() can be called in interrupt context, > > > 202 * so cache the vm_struct. > > > 203 */ > > > 204 if (stack) { > > > 205 tsk->stack_vm_area = find_vm_area(stack); > > > 206 } > > > 207 return stack; > > > 208 #else > > > > Could you check the state of the above process (pid 6506)? Does it still > > own its stack? > > Although I can reproduce the splat on kmemleak, getting it to trigger > at a point I can stop the kernel and inspect the process seems rather hard.
Can you make the kernel BUG_ON in this case and check the vmcore?
> > From a quick check I do not see any leak there either. > > Then in that case what about:
This just disables the kmemleak altogether which doesn't sound like a good idea to me.
> diff --git a/kernel/fork.c b/kernel/fork.c > index 937ba59709c9..3c96aafa1f82 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -196,6 +196,7 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node) > PAGE_KERNEL, > 0, node, __builtin_return_address(0)); > > + kmemleak_ignore(stack); > /* > * We can't call find_vm_area() in interrupt context, and > * free_thread_stack() can be called in interrupt context, > > I no longer get the spurious splats from kmemleak after this. > > Luis
-- Michal Hocko SUSE Labs
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