Re: [PATCH] lib/test_hmm: fix memory leak in dmirror_migrate_to_system()

[Alistair Popple]

On 2026-05-28 at 11:13 +1000, Hao Ge <hao.ge@xxxxxxxxx> wrote...
> Move the kvcalloc() calls after the early return checks to avoid
> leaking src_pfns and dst_pfns when end < start or mmget_not_zero()
> fails.

Thanks.

Reviewed-by: Alistair Popple <apopple@xxxxxxxxxx>

> Fixes: 775465fd26a3 ("lib/test_hmm: add zone device private THP test infrastructure")
> Reported-by: Sashiko <sashiko-bot@xxxxxxxxxx>
> Signed-off-by: Hao Ge <hao.ge@xxxxxxxxx>
> ---
> Sashiko report: https://sashiko.dev/#/patchset/20260513082525.154036-1-hao.ge@xxxxxxxxx
> 
> It looks like the other issue reported by Sashiko (dmirror_devmem_fault()
> leaking args.src/args.dst on migrate_vma_setup() failure) may have already
> been addressed in mm-new by 84808b0e9f75 ("lib/test_hmm: fix error path in
> dmirror_devmem_fault()").
> ---
>  lib/test_hmm.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/test_hmm.c b/lib/test_hmm.c
> index 213504915737..0c02871b97ba 100644
> --- a/lib/test_hmm.c
> +++ b/lib/test_hmm.c
> @@ -1111,9 +1111,6 @@ static int dmirror_migrate_to_system(struct dmirror *dmirror,
>  	unsigned long *src_pfns;
>  	unsigned long *dst_pfns;
>  
> -	src_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
> -	dst_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);
> -
>  	start = cmd->addr;
>  	end = start + size;
>  	if (end < start)
> @@ -1123,6 +1120,9 @@ static int dmirror_migrate_to_system(struct dmirror *dmirror,
>  	if (!mmget_not_zero(mm))
>  		return -EINVAL;
>  
> +	src_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*src_pfns), GFP_KERNEL | __GFP_NOFAIL);
> +	dst_pfns = kvcalloc(PTRS_PER_PTE, sizeof(*dst_pfns), GFP_KERNEL | __GFP_NOFAIL);
> +
>  	cmd->cpages = 0;
>  	mmap_read_lock(mm);
>  	for (addr = start; addr < end; addr = next) {
> -- 
> 2.25.1
> 
>