Re: [Linux Kernel Bug] memory leak in posix_clock_open

[Chenyuan Yang]

Dear Linux Developers,

I am reaching out to kindly inquire whether there have been any recent
updates or progress regarding the memory leak issue.
If you have any questions about the reproducer or config, please let me know.

Best,
Chenyuan


On Wed, Jan 24, 2024 at 10:22 AM Chenyuan Yang <chenyuan0y@xxxxxxxxx> wrote:
>
> Dear Linux Developers for Posix Timer,
>
> We encountered "memory leak in posix_clock_open" when testing the
> posix timer with
> Syzkaller and our generated specifications.
>
> ```
> BUG: memory leak
> unreferenced object 0xffff888000f66fa0 (size 16):
>   comm "syz-executor.0", pid 21073, jiffies 4295079945 (age 8.800s)
>   hex dump (first 16 bytes):
>     00 b8 d6 0d 80 88 ff ff 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff8162788a>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:42 [inline]
>     [<ffffffff8162788a>] slab_post_alloc_hook mm/slab.h:766 [inline]
>     [<ffffffff8162788a>] slab_alloc_node mm/slub.c:3478 [inline]
>     [<ffffffff8162788a>] __kmem_cache_alloc_node+0x2fa/0x3e0 mm/slub.c:3517
>     [<ffffffff81572354>] kmalloc_trace+0x24/0x90 mm/slab_common.c:1098
>     [<ffffffff81388b0e>] kmalloc include/linux/slab.h:600 [inline]
>     [<ffffffff81388b0e>] kzalloc include/linux/slab.h:721 [inline]
>     [<ffffffff81388b0e>] posix_clock_open+0x5e/0xe0
> kernel/time/posix-clock.c:126
>     [<ffffffff81692d69>] chrdev_open+0x119/0x340 fs/char_dev.c:414
>     [<ffffffff81680706>] do_dentry_open+0x336/0x9e0 fs/open.c:948
>     [<ffffffff816a9659>] do_open fs/namei.c:3622 [inline]
>     [<ffffffff816a9659>] path_openat+0x1799/0x1b00 fs/namei.c:3779
>     [<ffffffff816aa5ce>] do_filp_open+0xce/0x1b0 fs/namei.c:3809
>     [<ffffffff816843ed>] do_sys_openat2+0xdd/0x130 fs/open.c:1440
>     [<ffffffff81684d53>] do_sys_open fs/open.c:1455 [inline]
>     [<ffffffff81684d53>] __do_sys_openat fs/open.c:1471 [inline]
>     [<ffffffff81684d53>] __se_sys_openat fs/open.c:1466 [inline]
>     [<ffffffff81684d53>] __x64_sys_openat+0x83/0xe0 fs/open.c:1466
>     [<ffffffff84ae676f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
>     [<ffffffff84ae676f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
>     [<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b
>
> BUG: leak checking failed
> ```
> I have attached the reproducible C program and its configuration for
> this crash. Please note that the C program has not been minimized
> because there were issues with syz-repro.
>
> For this memory leak, it seems that the `pccontext` allocated by
> kzalloc (https://elixir.bootlin.com/linux/v6.7/source/kernel/time/posix-clock.c#L126)
> is not released correctly.
>
> If you have any questions or require more information, please feel
> free to contact us.
>
> Reported-by: Chenyuan Yang <chenyuan0y@xxxxxxxxx>
>
> Best,
> Chenyuan