Re: [PATCH v6 04/14] arm64: kexec_file: Fix CMA page leaks in segment placement retry loops

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [High] mm: kexec_file_load infinite loop due to unconstrained CMA retry
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commit 897e1cdce0bd14dc7b700f2043c1f14c66a40791
Author: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>

arm64: kexec_file: Fix CMA page leaks in segment placement retry loops

This commit fixes a memory leak in the kexec image placement retry loop.
It explicitly releases the associated CMA buffers in the failure paths
before the segment count is reduced.

> diff --git a/arch/arm64/kernel/kexec_image.c b/arch/arm64/kernel/kexec_image.c
> index b70f4df15a1ae..ffcb7f9075e62 100644
> --- a/arch/arm64/kernel/kexec_image.c
> +++ b/arch/arm64/kernel/kexec_image.c
> @@ -107,6 +107,7 @@ static void *image_load(struct kimage *image,
>  		 * We couldn't find space for the other segments; erase the
>  		 * kernel segment and try the next available hole.
>  		 */
> +		kexec_free_segment_cma(image, kernel_segment_number);
>  		image->nr_segments -= 1;
>  		kbuf.buf_min = kernel_segment->mem + kernel_segment->memsz;
>  		kbuf.mem = KEXEC_BUF_MEM_UNKNOWN;

[Severity: High]
Does freeing the CMA segment here create an infinite loop?

The loop updates kbuf.buf_min to search past the current kernel segment
expecting the next kexec_add_buffer() call to allocate from a new hole.

However, kexec_alloc_contig() allocates via CMA:

kernel/kexec_file.c:kexec_alloc_contig() {
    ...
    p = dma_alloc_from_contiguous(NULL, nr_pages,
                                  get_order(kbuf->buf_align), true);
    ...
}

The underlying CMA allocator completely ignores kbuf->buf_min and
kbuf->buf_max. Since the CMA block was just freed, the allocator will
repeatedly return the exact same physically contiguous block. 

If load_other_segments() fails due to layout constraints (like dtb or
initrd placement), it will run again with the identical memory layout, fail
for the exact same reason, and loop infinitely causing a system hang.

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Sashiko AI review · https://sashiko.dev/#/patchset/20260921090450.807575-1-ruanjinjie@xxxxxxxxxx?part=4