2023-10-15 20:27:09

by Pedro Falcato

Subject: [PATCH] mm: kmsan: Panic on failure to allocate early boot metadata

Given large enough allocations and a machine with low enough memory (i.e
a default QEMU VM), it's entirely possible that
kmsan_init_alloc_meta_for_range's shadow+origin allocation fails.

Instead of eating a NULL deref kernel oops, check explicitly for memblock_alloc()
failure and panic with a nice error message.

Signed-off-by: Pedro Falcato <[email protected]>
---
mm/kmsan/shadow.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
index 87318f9170f..3dae3d9c0b3 100644
--- a/mm/kmsan/shadow.c
+++ b/mm/kmsan/shadow.c
@@ -285,12 +285,18 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
size = PAGE_ALIGN((u64)end - (u64)start);
shadow = memblock_alloc(size, PAGE_SIZE);
origin = memblock_alloc(size, PAGE_SIZE);
+
+ if (!shadow || !origin)
+ panic("%s: Failed to allocate metadata memory for early boot range "
+ "of size %llu",
+ __func__, size);
+
for (u64 addr = 0; addr < size; addr += PAGE_SIZE) {
page = virt_to_page_or_null((char *)start + addr);
- shadow_p = virt_to_page_or_null((char *)shadow + addr);
+ shadow_p = virt_to_page((char *)shadow + addr);
set_no_shadow_origin_page(shadow_p);
shadow_page_for(page) = shadow_p;
- origin_p = virt_to_page_or_null((char *)origin + addr);
+ origin_p = virt_to_page((char *)origin + addr);
set_no_shadow_origin_page(origin_p);
origin_page_for(page) = origin_p;
}
--
2.42.0

2023-10-15 20:35:52

by Pedro Falcato

Subject: Re: [PATCH] mm: kmsan: Panic on failure to allocate early boot metadata

On Sun, Oct 15, 2023 at 9:26 PM Pedro Falcato <[email protected]> wrote:
>
> Given large enough allocations and a machine with low enough memory (i.e
> a default QEMU VM), it's entirely possible that
> kmsan_init_alloc_meta_for_range's shadow+origin allocation fails.

Ugh, forgot to run checkpatch.pl until it was too late :/

> Instead of eating a NULL deref kernel oops, check explicitly for memblock_alloc()

If there's no need for a v2, please wrap the above line and...

> failure and panic with a nice error message.
>
> Signed-off-by: Pedro Falcato <[email protected]>
> ---
> mm/kmsan/shadow.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
> index 87318f9170f..3dae3d9c0b3 100644
> --- a/mm/kmsan/shadow.c
> +++ b/mm/kmsan/shadow.c
> @@ -285,12 +285,18 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
> size = PAGE_ALIGN((u64)end - (u64)start);
> shadow = memblock_alloc(size, PAGE_SIZE);
> origin = memblock_alloc(size, PAGE_SIZE);
> +
> + if (!shadow || !origin)
> + panic("%s: Failed to allocate metadata memory for early boot range "
> + "of size %llu",

unwrap this string like this:
"%s: Failed to allocate metadata memory for early boot range of size %llu",

Silly mistake...

--
Pedro

2023-10-16 07:25:32

by Marco Elver

Subject: Re: [PATCH] mm: kmsan: Panic on failure to allocate early boot metadata

On Sun, 15 Oct 2023 at 22:35, Pedro Falcato <[email protected]> wrote:
>
> On Sun, Oct 15, 2023 at 9:26 PM Pedro Falcato <[email protected]> wrote:
> >
> > Given large enough allocations and a machine with low enough memory (i.e
> > a default QEMU VM), it's entirely possible that
> > kmsan_init_alloc_meta_for_range's shadow+origin allocation fails.
>
> Ugh, forgot to run checkpatch.pl until it was too late :/
>
> > Instead of eating a NULL deref kernel oops, check explicitly for memblock_alloc()
>
> If there's no need for a v2, please wrap the above line and...

Probably easier to send v2.

Otherwise looks good.

> > failure and panic with a nice error message.
> >
> > Signed-off-by: Pedro Falcato <[email protected]>
> > ---
> > mm/kmsan/shadow.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/mm/kmsan/shadow.c b/mm/kmsan/shadow.c
> > index 87318f9170f..3dae3d9c0b3 100644
> > --- a/mm/kmsan/shadow.c
> > +++ b/mm/kmsan/shadow.c
> > @@ -285,12 +285,18 @@ void __init kmsan_init_alloc_meta_for_range(void *start, void *end)
> > size = PAGE_ALIGN((u64)end - (u64)start);
> > shadow = memblock_alloc(size, PAGE_SIZE);
> > origin = memblock_alloc(size, PAGE_SIZE);
> > +
> > + if (!shadow || !origin)
> > + panic("%s: Failed to allocate metadata memory for early boot range "
> > + "of size %llu",
>
> unwrap this string like this:
> "%s: Failed to allocate metadata memory for early boot range of size %llu",
>
> Silly mistake...
>
> --
> Pedro