2022-11-24 04:23:38

by Jiasheng Jiang

Subject: [PATCH] mm/vmalloc: Add check for KMEM_CACHE

As KMEM_CACHE may return NULL pointer, it should
be better to check the return value in order to
avoid NULL pointer dereference in kmem_cache_zalloc.

Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap allocation")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
mm/vmalloc.c | 18 ++++++++++--------
1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ccaa461998f3..df3e59f614cc 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2426,15 +2426,17 @@ void __init vmalloc_init(void)
}

/* Import existing vmlist entries. */
- for (tmp = vmlist; tmp; tmp = tmp->next) {
- va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
- if (WARN_ON_ONCE(!va))
- continue;
+ if (!WARN_ON_ONCE(!vmap_area_cachep)) {
+ for (tmp = vmlist; tmp; tmp = tmp->next) {
+ va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
+ if (WARN_ON_ONCE(!va))
+ continue;

- va->va_start = (unsigned long)tmp->addr;
- va->va_end = va->va_start + tmp->size;
- va->vm = tmp;
- insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
+ va->va_start = (unsigned long)tmp->addr;
+ va->va_end = va->va_start + tmp->size;
+ va->vm = tmp;
+ insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
+ }
}

/*
--
2.25.1

2022-11-24 04:54:18

by Andrew Morton

Subject: Re: [PATCH] mm/vmalloc: Add check for KMEM_CACHE

On Thu, 24 Nov 2022 12:02:26 +0800 Jiasheng Jiang <[email protected]> wrote:

> As KMEM_CACHE may return NULL pointer, it should
> be better to check the return value in order to
> avoid NULL pointer dereference in kmem_cache_zalloc.
>
> ...
>
> @@ -2426,15 +2426,17 @@ void __init vmalloc_init(void)

Linux assumes that allocation attempts from __init code will succeed.

Because if they fail so early in the boot process, the system is so
utterly messed up that we may as well just go oops.

2022-11-24 05:16:34

by Matthew Wilcox

Subject: Re: [PATCH] mm/vmalloc: Add check for KMEM_CACHE

On Thu, Nov 24, 2022 at 12:02:26PM +0800, Jiasheng Jiang wrote:
> As KMEM_CACHE may return NULL pointer, it should
> be better to check the return value in order to
> avoid NULL pointer dereference in kmem_cache_zalloc.

You've made the code more complex. And for what? If that
call fails, the system will not boot under any circumstances.

NAK this patch, and any more like it.

> Fixes: 68ad4a330433 ("mm/vmalloc.c: keep track of free blocks for vmap allocation")
> Signed-off-by: Jiasheng Jiang <[email protected]>
> ---
> mm/vmalloc.c | 18 ++++++++++--------
> 1 file changed, 10 insertions(+), 8 deletions(-)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index ccaa461998f3..df3e59f614cc 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2426,15 +2426,17 @@ void __init vmalloc_init(void)
> }
>
> /* Import existing vmlist entries. */
> - for (tmp = vmlist; tmp; tmp = tmp->next) {
> - va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
> - if (WARN_ON_ONCE(!va))
> - continue;
> + if (!WARN_ON_ONCE(!vmap_area_cachep)) {
> + for (tmp = vmlist; tmp; tmp = tmp->next) {
> + va = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
> + if (WARN_ON_ONCE(!va))
> + continue;
>
> - va->va_start = (unsigned long)tmp->addr;
> - va->va_end = va->va_start + tmp->size;
> - va->vm = tmp;
> - insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
> + va->va_start = (unsigned long)tmp->addr;
> + va->va_end = va->va_start + tmp->size;
> + va->vm = tmp;
> + insert_vmap_area(va, &vmap_area_root, &vmap_area_list);
> + }
> }
>
> /*
> --
> 2.25.1
>
>