Re: [PATCH 1/2] RISC-V: kexec: Fix memory leak of fdt buffer

[Conor Dooley <conor@kernel.org>]

On Fri, Nov 04, 2022 at 05:56:57PM +0800, Li Huafei wrote:
> This is reported by kmemleak detector:
> 
> unreferenced object 0xff60000082864000 (size 9588):
>   comm "kexec", pid 146, jiffies 4294900634 (age 64.788s)
>   hex dump (first 32 bytes):
>     d0 0d fe ed 00 00 12 ed 00 00 00 48 00 00 11 40  ...........H...@
>     00 00 00 28 00 00 00 11 00 00 00 02 00 00 00 00  ...(............
>   backtrace:
>     [<00000000f95b17c4>] kmemleak_alloc+0x34/0x3e
>     [<00000000b9ec8e3e>] kmalloc_order+0x9c/0xc4
>     [<00000000a95cf02e>] kmalloc_order_trace+0x34/0xb6
>     [<00000000f01e68b4>] __kmalloc+0x5c2/0x62a
>     [<000000002bd497b2>] kvmalloc_node+0x66/0xd6
>     [<00000000906542fa>] of_kexec_alloc_and_setup_fdt+0xa6/0x6ea
>     [<00000000e1166bde>] elf_kexec_load+0x206/0x4ec
>     [<0000000036548e09>] kexec_image_load_default+0x40/0x4c
>     [<0000000079fbe1b4>] sys_kexec_file_load+0x1c4/0x322
>     [<0000000040c62c03>] ret_from_syscall+0x0/0x2
> 
> In elf_kexec_load(), a buffer is allocated via kvmalloc() to store fdt.
> While it's not freed back to system when kexec kernel is reloaded or
> unloaded.  Then memory leak is caused.  Fix it by introducing riscv
> specific function arch_kimage_file_post_load_cleanup(), and freeing the
> buffer there.
> 
> Fixes: 6261586e0c91 ("RISC-V: Add kexec_file support")
> Signed-off-by: Li Huafei <lihuafei1@huawei.com>

Both of these bits of cleanup seem to echo what's the case on arm64.
Seems reasonable to me..
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>

> ---
>  arch/riscv/include/asm/kexec.h |  5 +++++
>  arch/riscv/kernel/elf_kexec.c  | 10 ++++++++++
>  2 files changed, 15 insertions(+)
> 
> diff --git a/arch/riscv/include/asm/kexec.h b/arch/riscv/include/asm/kexec.h
> index eee260e8ab30..2b56769cb530 100644
> --- a/arch/riscv/include/asm/kexec.h
> +++ b/arch/riscv/include/asm/kexec.h
> @@ -39,6 +39,7 @@ crash_setup_regs(struct pt_regs *newregs,
>  #define ARCH_HAS_KIMAGE_ARCH
>  
>  struct kimage_arch {
> +	void *fdt; /* For CONFIG_KEXEC_FILE */
>  	unsigned long fdt_addr;
>  };
>  
> @@ -62,6 +63,10 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
>  				     const Elf_Shdr *relsec,
>  				     const Elf_Shdr *symtab);
>  #define arch_kexec_apply_relocations_add arch_kexec_apply_relocations_add
> +
> +struct kimage;
> +int arch_kimage_file_post_load_cleanup(struct kimage *image);
> +#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
>  #endif
>  
>  #endif
> diff --git a/arch/riscv/kernel/elf_kexec.c b/arch/riscv/kernel/elf_kexec.c
> index 0cb94992c15b..ff30fcb43f47 100644
> --- a/arch/riscv/kernel/elf_kexec.c
> +++ b/arch/riscv/kernel/elf_kexec.c
> @@ -21,6 +21,14 @@
>  #include <linux/memblock.h>
>  #include <asm/setup.h>
>  
> +int arch_kimage_file_post_load_cleanup(struct kimage *image)
> +{
> +	kvfree(image->arch.fdt);
> +	image->arch.fdt = NULL;
> +
> +	return kexec_image_post_load_cleanup_default(image);
> +}
> +
>  static int riscv_kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
>  				struct kexec_elf_info *elf_info, unsigned long old_pbase,
>  				unsigned long new_pbase)
> @@ -298,6 +306,8 @@ static void *elf_kexec_load(struct kimage *image, char *kernel_buf,
>  		pr_err("Error add DTB kbuf ret=%d\n", ret);
>  		goto out_free_fdt;
>  	}
> +	/* Cache the fdt buffer address for memory cleanup */
> +	image->arch.fdt = fdt;
>  	pr_notice("Loaded device tree at 0x%lx\n", kbuf.mem);
>  	goto out;
>  
> -- 
> 2.17.1
> 

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