[PATCH] x86: uv: Fix potential NULL pointer dereference of kmalloc_node

[PATCH] x86: uv: Fix potential NULL pointer dereference of kmalloc_node

[Aditya Pakki]

kmalloc_node might fail to allocate memory for thp field. This fix
attempts to avoid a potential NULL pointer dereference.

Signed-off-by: Aditya Pakki <pakki001@umn.edu>
---
 arch/x86/platform/uv/tlb_uv.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
index a4130b84d1ff..5a6d51e30a36 100644
--- a/arch/x86/platform/uv/tlb_uv.c
+++ b/arch/x86/platform/uv/tlb_uv.c
@@ -2011,6 +2011,9 @@ static void make_per_cpu_thp(struct bau_control *smaster)
 	size_t hpsz = sizeof(struct hub_and_pnode) * num_possible_cpus();
 
 	smaster->thp = kmalloc_node(hpsz, GFP_KERNEL, smaster->osnode);
+	if (!smaster->thp)
+		return;
+
 	memset(smaster->thp, 0, hpsz);
 	for_each_present_cpu(cpu) {
 		smaster->thp[cpu].pnode = uv_cpu_hub_info(cpu)->pnode;
-- 
2.17.1

Re: [PATCH] x86: uv: Fix potential NULL pointer dereference of kmalloc_node

[Joe Perches]

On Sat, 2019-03-02 at 15:09 -0600, Aditya Pakki wrote:
> kmalloc_node might fail to allocate memory for thp field. This fix
> attempts to avoid a potential NULL pointer dereference.

right

> diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
[]
> @@ -2011,6 +2011,9 @@ static void make_per_cpu_thp(struct bau_control *smaster)
>  	size_t hpsz = sizeof(struct hub_and_pnode) * num_possible_cpus();
>  
>  	smaster->thp = kmalloc_node(hpsz, GFP_KERNEL, smaster->osnode);
> +	if (!smaster->thp)
> +		return;
> +
>  	memset(smaster->thp, 0, hpsz);

Could use kzalloc_node as well

Re: [PATCH] x86: uv: Fix potential NULL pointer dereference of kmalloc_node

[Gustavo A. R. Silva]

Hi Aditya,

On 3/2/19 3:09 PM, Aditya Pakki wrote:
> kmalloc_node might fail to allocate memory for thp field. This fix
> attempts to avoid a potential NULL pointer dereference.
>

If this was detected by any static analyzer, please mention the
tool in the commit log.

Also, notice that this code does not apply to linux-next.

Thanks
--
Gustavo

> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  arch/x86/platform/uv/tlb_uv.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
> index a4130b84d1ff..5a6d51e30a36 100644
> --- a/arch/x86/platform/uv/tlb_uv.c
> +++ b/arch/x86/platform/uv/tlb_uv.c
> @@ -2011,6 +2011,9 @@ static void make_per_cpu_thp(struct bau_control *smaster)
>  	size_t hpsz = sizeof(struct hub_and_pnode) * num_possible_cpus();
>  
>  	smaster->thp = kmalloc_node(hpsz, GFP_KERNEL, smaster->osnode);
> +	if (!smaster->thp)
> +		return;
> +
>  	memset(smaster->thp, 0, hpsz);
>  	for_each_present_cpu(cpu) {
>  		smaster->thp[cpu].pnode = uv_cpu_hub_info(cpu)->pnode;
> 

Re: [PATCH] x86: uv: Fix potential NULL pointer dereference of kmalloc_node

[Peter Zijlstra]

On Sat, Mar 02, 2019 at 03:09:04PM -0600, Aditya Pakki wrote:
> kmalloc_node might fail to allocate memory for thp field. This fix
> attempts to avoid a potential NULL pointer dereference.
> 
> Signed-off-by: Aditya Pakki <pakki001@umn.edu>
> ---
>  arch/x86/platform/uv/tlb_uv.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c
> index a4130b84d1ff..5a6d51e30a36 100644
> --- a/arch/x86/platform/uv/tlb_uv.c
> +++ b/arch/x86/platform/uv/tlb_uv.c
> @@ -2011,6 +2011,9 @@ static void make_per_cpu_thp(struct bau_control *smaster)
>  	size_t hpsz = sizeof(struct hub_and_pnode) * num_possible_cpus();
>  
>  	smaster->thp = kmalloc_node(hpsz, GFP_KERNEL, smaster->osnode);
> +	if (!smaster->thp)
> +		return;

This is init code; memeory allocation is 'unlikely' to fail. If it were
to fail, we'd have gotten a nice crash pinpointing the failure.

Now, we boot but get weird crashes later. Note how the rest of the code
assumes smaster->thp to be set. How is that any better?