2021-06-18 13:16:33

by Andy Shevchenko

Subject: Re: [PATCH v1] mm: slub: fix the leak of alloc/free traces debugfs interface

On Fri, Jun 18, 2021 at 3:38 PM Faiyaz Mohammed <[email protected]> wrote:
>
> fix the leak of alloc/free traces debugfs interface, reported

Fix

> by kmemleak like below,
>
> unreferenced object 0xffff00091ae1b540 (size 64):
> comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
> hex dump (first 32 bytes):
> 02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b ........kkkkkkkk
> 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
> backtrace:
> [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
> [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
> [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
> slab_debugfs_start at mm/slub.c:5831
> [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
> [<ffff8000107b4b84>] seq_read+0x28c/0x418
> [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
> [<ffff800010738f24>] vfs_read+0x104/0x340
> [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
> [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
> [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
> [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
> [<ffff800011138528>] el0_svc+0x20/0x30
> [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
> [<ffff80001001259c>] el0t_64_sync+0x178/0x17c

Can you shrink this a bit?

> Fixes: 84a2bdb1b458fc968d6d9e07dab388dc679bd747 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")

We use 12, which is shorter.

> Link: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/slub.c?h=next-20210617&id=84a2bdb1b458fc968d6d9e07dab388dc679bd747

>

Must be no blank lines in the tag block.

> Signed-off-by: Faiyaz Mohammed <[email protected]>

...

> static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
> {
> - loff_t *spos = v;
> struct loc_track *t = seq->private;
>
> + v = ppos;
> if (*ppos < t->count) {
> - *ppos = ++*spos;
> - return spos;
> + ++*ppos;
> + return v;
> }
> - *ppos = ++*spos;
> + ++*ppos;
> return NULL;

Can it be

v = ppos;
++*ppos;
if (*ppos <= t->count)
return v;
return NULL;

? (basically the question is, is the comparison equivalent in this case or not)

> }

--
With Best Regards,
Andy Shevchenko

2021-06-20 16:12:29

by Faiyaz Mohammed

Subject: Re: [PATCH v1] mm: slub: fix the leak of alloc/free traces debugfs interface

On 6/18/2021 6:45 PM, Andy Shevchenko wrote:
> On Fri, Jun 18, 2021 at 3:38 PM Faiyaz Mohammed <[email protected]> wrote:
>>
>> fix the leak of alloc/free traces debugfs interface, reported
>
> Fix
>
Okay, I will update in next patch version.

>> by kmemleak like below,
>>
>> unreferenced object 0xffff00091ae1b540 (size 64):
>> comm "lsbug", pid 1607, jiffies 4294958291 (age 1476.340s)
>> hex dump (first 32 bytes):
>> 02 00 00 00 00 00 00 00 6b 6b 6b 6b 6b 6b 6b 6b ........kkkkkkkk
>> 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b 6b kkkkkkkkkkkkkkkk
>> backtrace:
>> [<ffff8000106b06b8>] slab_post_alloc_hook+0xa0/0x418
>> [<ffff8000106b5c7c>] kmem_cache_alloc_trace+0x1e4/0x378
>> [<ffff8000106b5e40>] slab_debugfs_start+0x30/0x50
>> slab_debugfs_start at mm/slub.c:5831
>> [<ffff8000107b3dbc>] seq_read_iter+0x214/0xd50
>> [<ffff8000107b4b84>] seq_read+0x28c/0x418
>> [<ffff8000109560b4>] full_proxy_read+0xdc/0x148
>> [<ffff800010738f24>] vfs_read+0x104/0x340
>> [<ffff800010739ee0>] ksys_read+0xf8/0x1e0
>> [<ffff80001073a03c>] __arm64_sys_read+0x74/0xa8
>> [<ffff8000100358d4>] invoke_syscall.constprop.0+0xdc/0x1d8
>> [<ffff800010035ab4>] do_el0_svc+0xe4/0x298
>> [<ffff800011138528>] el0_svc+0x20/0x30
>> [<ffff800011138b08>] el0t_64_sync_handler+0xb0/0xb8
>> [<ffff80001001259c>] el0t_64_sync+0x178/0x17c
>
> Can you shrink this a bit?
>
Okay

>> Fixes: 84a2bdb1b458fc968d6d9e07dab388dc679bd747 ("mm: slub: move sysfs slab alloc/free interfaces to debugfs")
>
> We use 12, which is shorter.
>
>> Link: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/mm/slub.c?h=next-20210617&id=84a2bdb1b458fc968d6d9e07dab388dc679bd747
>
>>
>
> Must be no blank lines in the tag block.
> >> Signed-off-by: Faiyaz Mohammed <[email protected]>
>
Okay
> ...
>
>> static void *slab_debugfs_next(struct seq_file *seq, void *v, loff_t *ppos)
>> {
>> - loff_t *spos = v;
>> struct loc_track *t = seq->private;
>>
>> + v = ppos;
>> if (*ppos < t->count) {
>> - *ppos = ++*spos;
>> - return spos;
>> + ++*ppos;
>> + return v;
>> }
>> - *ppos = ++*spos;
>> + ++*ppos;
>> return NULL;
>
> Can it be
>
> v = ppos;
> ++*ppos;
> if (*ppos <= t->count> return v;
> return NULL;
>
> ? (basically the question is, is the comparison equivalent in this case or not)
>
>> }
>Yes, we can update it and slab_debugfs_show has the index check as well.
I will update in next patch version.

Thanks and regards,
Mohammed Faiyaz