linux-kernel - Re: [PATCH v2] mm/hugetlb: Fix incorrect error return from hugetlb_reserve

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Message-ID: <20251124192803.GK153257@nvidia.com>
Date: Mon, 24 Nov 2025 15:28:03 -0400
From: Jason Gunthorpe <jgg@...dia.com>
To: Shameer Kolothum <skolothumtho@...dia.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, muchun.song@...ux.dev,
	osalvador@...e.de, vivek.kasireddy@...el.com,
	joshua.hahnjy@...il.com, nicolinc@...dia.com, nathanc@...dia.com,
	mochs@...dia.com
Subject: Re: [PATCH v2] mm/hugetlb: Fix incorrect error return from
 hugetlb_reserve_pages()

On Fri, Oct 24, 2025 at 10:42:40AM +0100, Shameer Kolothum wrote:
> The function hugetlb_reserve_pages() returns the number of pages added
> to the reservation map on success and a negative error code on failure
> (e.g. -EINVAL, -ENOMEM). However, in some error paths, it may return -1
> directly.
> 
> For example, a failure at:
> 
>     if (hugetlb_acct_memory(h, gbl_reserve) < 0)
>         goto out_put_pages;
> 
> results in returning -1 (since add = -1), which may be misinterpreted
> in userspace as -EPERM.
> 
> Fix this by explicitly capturing and propagating the return values from
> helper functions, and using -EINVAL for all other failure cases.
> 
> Fixes: 986f5f2b4be3 ("mm/hugetlb: make hugetlb_reserve_pages() return nr of entries updated")
> Signed-off-by: Shameer Kolothum <skolothumtho@...dia.com>
> ---
>  Addressed commenst from v1. Thanks!
>  https://lore.kernel.org/linux-mm/20251022102956.245736-1-skolothumtho@nvidia.com/
> ---
>  mm/hugetlb.c | 25 ++++++++++++++++++-------
>  1 file changed, 18 insertions(+), 7 deletions(-)

Reviewed-by: Jason Gunthorpe <jgg@...dia.com>

Jason