Re: [Linux Kernel Bug] memory leak in dvb_dmxdev_add_pid

[Chenyuan Yang]

Dear Linux Developers for DVB,

I am writing to inquire if there have been any updates regarding the
memory leak issue. The issue remains reproducible on the latest stable
Linux version (6.12-rc2, commit
8cf0b93919e13d1e8d4466eb4080a4c4d9d66d7b).

Thank you for your attention to this matter.

Best,
Chenyuan

On Sat, Mar 2, 2024 at 3:12 PM Chenyuan Yang <chenyuan0y@xxxxxxxxx> wrote:
>
> Dear Linux Developers for DVB,
>
> We encountered "memory leak in dvb_dmxdev_add_pid" when testing the
> DVB driver with Syzkaller and our generated specifications.
>
> The C reproducer and the config for the kernel are attached.
>
> The memory leak originates from the allocated dmxdev_feed structure,
> as referenced in the code at
> [https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-core/dmxdev.c#L881].
> This structure fails to be freed upon entering the code branch found
> at [https://elixir.bootlin.com/linux/latest/source/drivers/media/dvb-core/dmxdev.c#L891].
>
> ```
> ioctl$KGPT_DMX_START(r0, 0x6f29, 0x0)
> BUG: memory leak
> unreferenced object 0xffff88802e9ae7e0 (size 32):
>   comm "syz-executor.0", pid 27777, jiffies 4295115050 (age 15.550s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     08 c0 6a 05 00 c9 ff ff 08 c0 6a 05 00 c9 ff ff  ..j.......j.....
>   backtrace:
>     [<ffffffff8169126f>] kmemleak_alloc_recursive
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/./include/linux/kmemleak.h:42
> [inline]
>     [<ffffffff8169126f>] slab_post_alloc_hook
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/mm/slab.h:766
> [inline]
>     [<ffffffff8169126f>] slab_alloc_node
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/mm/slub.c:3478
> [inline]
>     [<ffffffff8169126f>] __kmem_cache_alloc_node+0x2ff/0x3e0
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/mm/slub.c:3517
>     [<ffffffff815d9da9>] kmalloc_trace+0x29/0x90
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/mm/slab_common.c:1098
>     [<ffffffff83db2e09>] kmalloc
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/./include/linux/slab.h:600
> [inline]
>     [<ffffffff83db2e09>] kzalloc
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/./include/linux/slab.h:721
> [inline]
>     [<ffffffff83db2e09>] dvb_dmxdev_add_pid+0xa9/0x160
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/drivers/media/dvb-core/dmxdev.c:881
>     [<ffffffff83db48de>] dvb_dmxdev_pes_filter_set
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/drivers/media/dvb-core/dmxdev.c:956
> [inline]
>     [<ffffffff83db48de>] dvb_demux_do_ioctl+0x67e/0xa80
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/drivers/media/dvb-core/dmxdev.c:1076
>     [<ffffffff83db1252>] dvb_usercopy+0x82/0x220
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/drivers/media/dvb-core/dvbdev.c:986
>     [<ffffffff83db1b51>] dvb_demux_ioctl+0x31/0x40
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/drivers/media/dvb-core/dmxdev.c:1185
>     [<ffffffff8171ca88>] vfs_ioctl
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/fs/ioctl.c:51
> [inline]
>     [<ffffffff8171ca88>] __do_sys_ioctl
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/fs/ioctl.c:871
> [inline]
>     [<ffffffff8171ca88>] __se_sys_ioctl
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/fs/ioctl.c:857
> [inline]
>     [<ffffffff8171ca88>] __x64_sys_ioctl+0x108/0x150
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/fs/ioctl.c:857
>     [<ffffffff8540b150>] do_syscall_x64
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/arch/x86/entry/common.c:51
> [inline]
>     [<ffffffff8540b150>] do_syscall_64+0x40/0x110
> scratch/zijie-data/LLM-Kernel/spec-eval/shared_linux_builds/syzbot-leak-more_631373bc9e824969/arch/x86/entry/common.c:82
>     [<ffffffff8560008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b
> ```
>
> If you have any questions or require more information, please feel
> free to contact us.
>
> Reported-by: Chenyuan Yang <chenyuan0y@xxxxxxxxx>
>
> Best,
> Chenyuan