* [PATCH] mm: cma: Fix potential null dereference on pointer cma
@ 2021-03-16 10:04 Colin King
2021-03-16 18:09 ` Minchan Kim
2021-03-17 7:13 ` John Hubbard
0 siblings, 2 replies; 3+ messages in thread
From: Colin King @ 2021-03-16 10:04 UTC (permalink / raw)
To: Andrew Morton, Minchan Kim, John Hubbard, Stephen Rothwell,
Greg Kroah-Hartman, linux-mm
Cc: kernel-janitors, linux-kernel
From: Colin Ian King <colin.king@canonical.com>
At the start of the function there is a null pointer check on cma
and then branch to error handling label 'out'. The subsequent call
to cma_sysfs_fail_pages_count dereferences cma, hence there is a
potential null pointer deference issue. Fix this by only calling
cma_sysfs_fail_pages_count if cma is not null.
Addresses-Coverity: ("Dereference after null check")
Fixes: dc4764f7e9ac ("mm: cma: support sysfs")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
mm/cma.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/mm/cma.c b/mm/cma.c
index 6d4dbafdb318..90e27458ddb7 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -512,7 +512,8 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
cma_sysfs_alloc_pages_count(cma, count);
} else {
count_vm_event(CMA_ALLOC_FAIL);
- cma_sysfs_fail_pages_count(cma, count);
+ if (cma)
+ cma_sysfs_fail_pages_count(cma, count);
}
return page;
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: cma: Fix potential null dereference on pointer cma
2021-03-16 10:04 [PATCH] mm: cma: Fix potential null dereference on pointer cma Colin King
@ 2021-03-16 18:09 ` Minchan Kim
2021-03-17 7:13 ` John Hubbard
1 sibling, 0 replies; 3+ messages in thread
From: Minchan Kim @ 2021-03-16 18:09 UTC (permalink / raw)
To: Colin King
Cc: Andrew Morton, John Hubbard, Stephen Rothwell,
Greg Kroah-Hartman, linux-mm, kernel-janitors, linux-kernel
On Tue, Mar 16, 2021 at 10:04:33AM +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> At the start of the function there is a null pointer check on cma
> and then branch to error handling label 'out'. The subsequent call
> to cma_sysfs_fail_pages_count dereferences cma, hence there is a
> potential null pointer deference issue. Fix this by only calling
> cma_sysfs_fail_pages_count if cma is not null.
>
> Addresses-Coverity: ("Dereference after null check")
> Fixes: dc4764f7e9ac ("mm: cma: support sysfs")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Minchan Kim <minchan@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] mm: cma: Fix potential null dereference on pointer cma
2021-03-16 10:04 [PATCH] mm: cma: Fix potential null dereference on pointer cma Colin King
2021-03-16 18:09 ` Minchan Kim
@ 2021-03-17 7:13 ` John Hubbard
1 sibling, 0 replies; 3+ messages in thread
From: John Hubbard @ 2021-03-17 7:13 UTC (permalink / raw)
To: Colin King, Andrew Morton, Minchan Kim, Stephen Rothwell,
Greg Kroah-Hartman, linux-mm
Cc: kernel-janitors, linux-kernel
On 3/16/21 3:04 AM, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> At the start of the function there is a null pointer check on cma
> and then branch to error handling label 'out'. The subsequent call
> to cma_sysfs_fail_pages_count dereferences cma, hence there is a
> potential null pointer deference issue. Fix this by only calling
As far as I can tell, it's not possible to actually cause that null
failure with the existing kernel code paths. *Might* be worth mentioning
that here (unless I'm wrong), but either way, looks good, so:
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
thanks,
--
John Hubbard
NVIDIA
> cma_sysfs_fail_pages_count if cma is not null.
>
> Addresses-Coverity: ("Dereference after null check")
> Fixes: dc4764f7e9ac ("mm: cma: support sysfs")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> mm/cma.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/mm/cma.c b/mm/cma.c
> index 6d4dbafdb318..90e27458ddb7 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -512,7 +512,8 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
> cma_sysfs_alloc_pages_count(cma, count);
> } else {
> count_vm_event(CMA_ALLOC_FAIL);
> - cma_sysfs_fail_pages_count(cma, count);
> + if (cma)
> + cma_sysfs_fail_pages_count(cma, count);
> }
>
> return page;
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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