Hi,
> The CMA pages allocated for a kexec segment are released using the
> segment's memsz to calculate the number of pages. However, some
> architecture loaders modify the segment's memsz after allocation
> (e.g. arm64 subtracts text_offset), causing the release function to
> free fewer pages than were originally allocated, leaking the remaining
> CMA pages.
>
> Add a per-segment `segment_cma_pages` array to store the number of
> pages actually allocated from CMA. Populate it during
> kexec_add_buffer() using the aligned memsz, and use it in
> kimage_free_cma() to accurately release all allocated pages.
>
> This avoids relying on the potentially modified segment->memsz and
> prevents silent CMA memory leaks.
>
> Cc: Andrew Morton <[email protected]>
> Cc: Baoquan He <[email protected]>
> Cc: Mike Rapoport <[email protected]>
> Cc: Pasha Tatashin <[email protected]>
> Cc: Pratyush Yadav <[email protected]>
> Cc: Brian Mak <[email protected]>
> Cc: Pingfan Liu <[email protected]>
> Cc: Sourabh Jain <[email protected]>
> Cc: Justinien Bouron <[email protected]>
> Cc: Li Chen <[email protected]>
> Cc: [email protected]
> Link:
> https://sashiko.dev/#/patchset/20260729031235.2840255-1-ruanjinjie%40huawei.com
> Fixes: 07d24902977e ("kexec: enable CMA based contiguous allocation")
> Signed-off-by: Jinjie Ruan <[email protected]>
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 0af8ae4fdd087..83c296c0eb6cc 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -349,6 +349,7 @@ struct kimage {
> unsigned long nr_segments;
> struct kexec_segment segment[KEXEC_SEGMENT_MAX];
> struct page *segment_cma[KEXEC_SEGMENT_MAX];
> + unsigned int segment_cma_pages[KEXEC_SEGMENT_MAX];
Can we universally use unsigned long for number of pages?
>
> struct list_head control_pages;
> struct list_head dest_pages;
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index dc770b9a6d053..611b15bb1369e 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -560,7 +560,7 @@ static void kimage_free_cma(struct kimage *image)
>
> for (i = 0; i < image->nr_segments; i++) {
> struct page *cma = image->segment_cma[i];
> - u32 nr_pages = image->segment[i].memsz >> PAGE_SHIFT;
> + unsigned int nr_pages = image->segment_cma_pages[i];
>
> if (!cma)
> continue;
> @@ -568,6 +568,7 @@ static void kimage_free_cma(struct kimage *image)
> arch_kexec_pre_free_pages(page_address(cma), nr_pages);
> dma_release_from_contiguous(NULL, cma, nr_pages);
> image->segment_cma[i] = NULL;
> + image->segment_cma_pages[i] = 0;
> }
>
> }
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 59fb9d71e9d86..bfae3fee7f2f9 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -670,7 +670,7 @@ static int kexec_walk_resources(struct kexec_buf *kbuf,
>
> static int kexec_alloc_contig(struct kexec_buf *kbuf)
> {
> - size_t nr_pages = kbuf->memsz >> PAGE_SHIFT;
> + size_t nr_pages = PFN_DOWN(kbuf->memsz);
> unsigned long mem;
> struct page *p;
>
> @@ -756,6 +756,8 @@ int kexec_locate_mem_hole(struct kexec_buf *kbuf)
> */
> int kexec_add_buffer(struct kexec_buf *kbuf)
> {
> + unsigned long nr_segments = kbuf->image->nr_segments;
> + size_t nr_pages;
> struct kexec_segment *ksegment;
> int ret;
>
> @@ -763,7 +765,7 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
> if (!kbuf->image->file_mode)
> return -EINVAL;
>
> - if (kbuf->image->nr_segments >= KEXEC_SEGMENT_MAX)
> + if (nr_segments >= KEXEC_SEGMENT_MAX)
> return -EINVAL;
>
> /*
> @@ -789,12 +791,18 @@ int kexec_add_buffer(struct kexec_buf *kbuf)
> return ret;
>
> /* Found a suitable memory range */
> - ksegment = &kbuf->image->segment[kbuf->image->nr_segments];
> + ksegment = &kbuf->image->segment[nr_segments];
> ksegment->kbuf = kbuf->buffer;
> ksegment->bufsz = kbuf->bufsz;
> ksegment->mem = kbuf->mem;
> ksegment->memsz = kbuf->memsz;
> - kbuf->image->segment_cma[kbuf->image->nr_segments] = kbuf->cma;
> + kbuf->image->segment_cma[nr_segments] = kbuf->cma;
> + if (kbuf->cma) {
> + nr_pages = (unsigned int)(PFN_DOWN(kbuf->memsz));
> + kbuf->image->segment_cma_pages[nr_segments] = nr_pages;
kbuf->image->segment_cma_pages[nr_segments] = nr_pages;
> + } else {
> + kbuf->image->segment_cma_pages[nr_segments] = 0;
> + }
I suggest to rename nr_pages to nr_cma_pages, initialize it to 0 at
declaration time and make this
if (kbuf->cma)
nr_cma_pages = PFN_DOWN(kbuf->memsz);
kbuf->image->segment_cma_pages[nr_segments] = nr_cma_pages;
--
Sincerely yours,
Mike.
