Re: [PATCH v2 1/6] kexec: Initialize ELF lowest address to ULONG_MAX

Hari Bathini
2025-01-23T10:04:33Z

On 21/01/25 5:24 pm, Sourabh Jain wrote:
> kexec_elf_load() loads an ELF executable and sets the address of the
> lowest PT_LOAD section to the address held by the lowest_load_addr
> function argument.
>
> To determine the lowest PT_LOAD address, a local variable lowest_addr
> (type unsigned long) is initialized to UINT_MAX. After loading each
> PT_LOAD, its address is compared to lowest_addr. If a loaded PT_LOAD
> address is lower, lowest_addr is updated. However, setting lowest_addr
> to UINT_MAX won't work when the kernel image is loaded above 4G, as the
> returned lowest PT_LOAD address would be invalid. This is resolved by
> initializing lowest_addr to ULONG_MAX instead.
>
> This issue was discovered while implementing crashkernel high/low
> reservation on the PowerPC architecture.
>

Acked-by: Hari Bathini <hbathini@linux.ibm.com>

> Fixes: a0458284f062 ("powerpc: Add support code for kexec_file_load()")
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Hari Bathini <hbathini@linux.ibm.com>
> Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
> Cc: Mahesh Salgaonkar <mahesh@linux.ibm.com>
> Cc: Michael Ellerman <mpe@ellerman.id.au>
> Cc: kexec@lists.infradead.org
> Cc: linuxppc-dev@lists.ozlabs.org
> Cc: linux-kernel@vger.kernel.org
> Acked-by: Baoquan He <bhe@redhat.com>
> Signed-off-by: Sourabh Jain <sourabhjain@linux.ibm.com>
> ---
> kernel/kexec_elf.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/kexec_elf.c b/kernel/kexec_elf.c
> index d3689632e8b9..3a5c25b2adc9 100644
> --- a/kernel/kexec_elf.c
> +++ b/kernel/kexec_elf.c
> @@ -390,7 +390,7 @@ int kexec_elf_load(struct kimage *image, struct elfhdr *ehdr,
> struct kexec_buf *kbuf,
> unsigned long *lowest_load_addr)
> {
> - unsigned long lowest_addr = UINT_MAX;
> + unsigned long lowest_addr = ULONG_MAX;
> int ret;
> size_t i;
>