On Mon, Oct 14, 2024 at 03:23:36AM +0000, Chen Ridong wrote:
> From: Chen Ridong <chenridong@xxxxxxxxxx>
>
> A memleak was found as bellow:
>
> unreferenced object 0xffff8881010d2a80 (size 32):
> comm "mkdir", pid 1559, jiffies 4294932666
> hex dump (first 32 bytes):
> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> 40 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 @...............
> backtrace (crc 2e7ef6fa):
> [<ffffffff81372754>] __kmalloc_node_noprof+0x394/0x470
> [<ffffffff813024ab>] alloc_shrinker_info+0x7b/0x1a0
> [<ffffffff813b526a>] mem_cgroup_css_online+0x11a/0x3b0
> [<ffffffff81198dd9>] online_css+0x29/0xa0
> [<ffffffff811a243d>] cgroup_apply_control_enable+0x20d/0x360
> [<ffffffff811a5728>] cgroup_mkdir+0x168/0x5f0
> [<ffffffff8148543e>] kernfs_iop_mkdir+0x5e/0x90
> [<ffffffff813dbb24>] vfs_mkdir+0x144/0x220
> [<ffffffff813e1c97>] do_mkdirat+0x87/0x130
> [<ffffffff813e1de9>] __x64_sys_mkdir+0x49/0x70
> [<ffffffff81f8c928>] do_syscall_64+0x68/0x140
> [<ffffffff8200012f>] entry_SYSCALL_64_after_hwframe+0x76/0x7e
>
> In the alloc_shrinker_info function, when shrinker_unit_alloc return
> err, the info won't be freed. Just fix it.
>
> Fixes: 307bececcd12 ("mm: shrinker: add a secondary array for shrinker_info::{map, nr_deferred}")
> Signed-off-by: Chen Ridong <chenridong@xxxxxxxxxx>
> ---
> mm/shrinker.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/mm/shrinker.c b/mm/shrinker.c
> index dc5d2a6fcfc4..92270413190d 100644
> --- a/mm/shrinker.c
> +++ b/mm/shrinker.c
> @@ -97,6 +97,7 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
>
> err:
> mutex_unlock(&shrinker_mutex);
> + kvfree(info);
> free_shrinker_info(memcg);
> return -ENOMEM;
> }
NAK. If in the future there going to one more error case after
rcu_assign_pointer() we will end up with double free.
This should be safer:
diff --git a/mm/shrinker.c b/mm/shrinker.c
index dc5d2a6fcfc4..763fd556bc7d 100644
--- a/mm/shrinker.c
+++ b/mm/shrinker.c
@@ -87,8 +87,10 @@ int alloc_shrinker_info(struct mem_cgroup *memcg)
if (!info)
goto err;
info->map_nr_max = shrinker_nr_max;
- if (shrinker_unit_alloc(info, NULL, nid))
+ if (shrinker_unit_alloc(info, NULL, nid)) {
+ kvfree(info);
goto err;
+ }
rcu_assign_pointer(memcg->nodeinfo[nid]->shrinker_info, info);
}
mutex_unlock(&shrinker_mutex);
--
Kiryl Shutsemau / Kirill A. Shutemov
