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Date:   Fri, 29 Oct 2021 18:31:32 +0200
From:   Philipp Rudo <prudo@redhat.com>
To:     Baoquan He <bhe@redhat.com>
Cc:     linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org,
        kexec@lists.infradead.org, dyoung@redhat.com,
        akpm@linux-foundation.org
Subject: Re: [PATCH] s390/kexec: fix memory leak of ipl report buffer
Message-ID: <20211029183132.20839ad0@rhtmp>
In-Reply-To: <20211029092635.14804-1-bhe@redhat.com>
References: <20211029092635.14804-1-bhe@redhat.com>
Organization: Red Hat inc.
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Hi Baoquan,

On Fri, 29 Oct 2021 17:26:35 +0800
Baoquan He <bhe@redhat.com> wrote:

> A memory leak is reported by kmemleak scanning:
> 
> unreferenced object 0x38000195000 (size 4096):
>   comm "kexec", pid 8548, jiffies 4294953647 (age 32443.270s)
>   hex dump (first 32 bytes):
>     00 00 00 c8 20 00 00 00 00 00 00 c0 02 80 00 00  .... ...........
>     40 40 40 40 40 40 40 40 00 00 00 00 00 00 00 00  @@@@@@@@........
>   backtrace:
>     [<0000000011a2f199>] __vmalloc_node_range+0xc0/0x140
>     [<0000000081fa2752>] vzalloc+0x5a/0x70
>     [<0000000063a4c92d>] ipl_report_finish+0x2c/0x180
>     [<00000000553304da>] kexec_file_add_ipl_report+0xf4/0x150
>     [<00000000862d033f>] kexec_file_add_components+0x124/0x160
>     [<000000000d2717bb>] arch_kexec_kernel_image_load+0x62/0x90
>     [<000000002e0373b6>] kimage_file_alloc_init+0x1aa/0x2e0
>     [<0000000060f2d14f>] __do_sys_kexec_file_load+0x17c/0x2c0
>     [<000000008c86fe5a>] __s390x_sys_kexec_file_load+0x40/0x50
>     [<000000001fdb9dac>] __do_syscall+0x1bc/0x1f0
>     [<000000003ee4258d>] system_call+0x78/0xa0
> 
> The ipl report buffer is allocated via vmalloc, while has no chance to free
> if the kexe loading is unloaded. This will cause obvious memory leak
> when kexec/kdump kernel is reloaded, manually, or triggered, e.g by
> memory hotplug.
> 
> Here, add struct kimage_arch to s390 to pass out the ipl report buffer
> address, and introduce arch dependent function
> arch_kimage_file_post_load_cleanup() to free it when unloaded.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>

other than a missing

Fixes: 99feaa717e55 ("s390/kexec_file: Create ipl report and pass to
next kernel")

the patch looks good to me.

Reviewed-by: Philipp Rudo <prudo@redhat.com>

> ---
>  arch/s390/include/asm/kexec.h         | 7 +++++++
>  arch/s390/kernel/machine_kexec_file.c | 9 +++++++++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kexec.h b/arch/s390/include/asm/kexec.h
> index ea398a05f643..9f16e99fb882 100644
> --- a/arch/s390/include/asm/kexec.h
> +++ b/arch/s390/include/asm/kexec.h
> @@ -74,6 +74,13 @@ void *kexec_file_add_components(struct kimage *image,
>  int arch_kexec_do_relocs(int r_type, void *loc, unsigned long val,
>  			 unsigned long addr);
>  
> +#define ARCH_HAS_KIMAGE_ARCH
> +
> +struct kimage_arch {
> +	void *ipl_buf;
> +};
> +
> +
>  extern const struct kexec_file_ops s390_kexec_image_ops;
>  extern const struct kexec_file_ops s390_kexec_elf_ops;
>  
> diff --git a/arch/s390/kernel/machine_kexec_file.c b/arch/s390/kernel/machine_kexec_file.c
> index f9e4baa64b67..584c48b631b2 100644
> --- a/arch/s390/kernel/machine_kexec_file.c
> +++ b/arch/s390/kernel/machine_kexec_file.c
> @@ -202,6 +202,7 @@ static int kexec_file_add_ipl_report(struct kimage *image,
>  	buf.buffer = ipl_report_finish(data->report);
>  	buf.bufsz = data->report->size;
>  	buf.memsz = buf.bufsz;
> +	image->arch.ipl_buf = buf.buffer;
>  
>  	data->memsz += buf.memsz;
>  
> @@ -321,3 +322,11 @@ int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
>  
>  	return kexec_image_probe_default(image, buf, buf_len);
>  }
> +
> +int arch_kimage_file_post_load_cleanup(struct kimage *image)
> +{
> +	kvfree(image->arch.ipl_buf);
> +	image->arch.ipl_buf = NULL;
> +
> +	return kexec_image_post_load_cleanup_default(image);
> +}