[PATCH] riscv: process: fix kernel info leakage

[PATCH] riscv: process: fix kernel info leakage

[Jisheng Zhang]

thread_struct's s[12] may contain random kernel memory content, which
may be finally leaked to userspace. This is a security hole. Fix it
by clearing the s[12] array in thread_struct when fork.

As for kthread case, it's better to clear the s[12] array as well.

Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
---

Previously, it's one of the series of "riscv: entry: further clean up
and VMAP_STACK fix". This is a fix, so I move it out of the series and
send it separately

 arch/riscv/kernel/process.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
index ceb9ebab6558..52002d54b163 100644
--- a/arch/riscv/kernel/process.c
+++ b/arch/riscv/kernel/process.c
@@ -164,6 +164,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
 	unsigned long tls = args->tls;
 	struct pt_regs *childregs = task_pt_regs(p);
 
+	memset(&p->thread.s, 0, sizeof(p->thread.s));
+
 	/* p->thread holds context to be restored by __switch_to() */
 	if (unlikely(args->fn)) {
 		/* Kernel thread */
-- 
2.37.2

Re: [PATCH] riscv: process: fix kernel info leakage

[Guo Ren]

On Sat, Oct 29, 2022 at 7:44 PM Jisheng Zhang <jszhang@kernel.org> wrote:
>
> thread_struct's s[12] may contain random kernel memory content, which
> may be finally leaked to userspace. This is a security hole. Fix it
> by clearing the s[12] array in thread_struct when fork.
>
> As for kthread case, it's better to clear the s[12] array as well.
>
> Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
>
> Previously, it's one of the series of "riscv: entry: further clean up
> and VMAP_STACK fix". This is a fix, so I move it out of the series and
> send it separately
>
>  arch/riscv/kernel/process.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index ceb9ebab6558..52002d54b163 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -164,6 +164,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>         unsigned long tls = args->tls;
>         struct pt_regs *childregs = task_pt_regs(p);
>
> +       memset(&p->thread.s, 0, sizeof(p->thread.s));
Tested-by: Guo Ren <guoren@kernel.org>

> +
>         /* p->thread holds context to be restored by __switch_to() */
>         if (unlikely(args->fn)) {
>                 /* Kernel thread */
> --
> 2.37.2
>


-- 
Best Regards
 Guo Ren

Re: [PATCH] riscv: process: fix kernel info leakage

[Conor Dooley]

On Sat, Oct 29, 2022 at 07:34:50PM +0800, Jisheng Zhang wrote:
> thread_struct's s[12] may contain random kernel memory content, which
> may be finally leaked to userspace. This is a security hole. Fix it
> by clearing the s[12] array in thread_struct when fork.
> 
> As for kthread case, it's better to clear the s[12] array as well.
> 
> Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> ---
> 
> Previously, it's one of the series of "riscv: entry: further clean up
> and VMAP_STACK fix". This is a fix, so I move it out of the series and
> send it separately

Should this not be carrying a R-b from Guo Ren from that series?
https://lore.kernel.org/linux-riscv/CAJF2gTSdVyAaM12T+7kXAdRPGS4VyuO08X1c7paE-n4Fr8OtRA@mail.gmail.com/
> 
>  arch/riscv/kernel/process.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/riscv/kernel/process.c b/arch/riscv/kernel/process.c
> index ceb9ebab6558..52002d54b163 100644
> --- a/arch/riscv/kernel/process.c
> +++ b/arch/riscv/kernel/process.c
> @@ -164,6 +164,8 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
>  	unsigned long tls = args->tls;
>  	struct pt_regs *childregs = task_pt_regs(p);
>  
> +	memset(&p->thread.s, 0, sizeof(p->thread.s));
> +
>  	/* p->thread holds context to be restored by __switch_to() */
>  	if (unlikely(args->fn)) {
>  		/* Kernel thread */
> -- 
> 2.37.2
> 

Re: [PATCH] riscv: process: fix kernel info leakage

[Palmer Dabbelt]

On Sat, 29 Oct 2022 19:34:50 +0800, Jisheng Zhang wrote:
> thread_struct's s[12] may contain random kernel memory content, which
> may be finally leaked to userspace. This is a security hole. Fix it
> by clearing the s[12] array in thread_struct when fork.
> 
> As for kthread case, it's better to clear the s[12] array as well.
> 
> 
> [...]

Applied, thanks!

[1/1] riscv: process: fix kernel info leakage
      https://git.kernel.org/palmer/c/6510c78490c4

Best regards,
-- 
Palmer Dabbelt <palmer@rivosinc.com>

Re: [PATCH] riscv: process: fix kernel info leakage

[patchwork-bot+linux-riscv]

Hello:

This patch was applied to riscv/linux.git (fixes)
by Palmer Dabbelt <palmer@rivosinc.com>:

On Sat, 29 Oct 2022 19:34:50 +0800 you wrote:
> thread_struct's s[12] may contain random kernel memory content, which
> may be finally leaked to userspace. This is a security hole. Fix it
> by clearing the s[12] array in thread_struct when fork.
> 
> As for kthread case, it's better to clear the s[12] array as well.
> 
> Fixes: 7db91e57a0ac ("RISC-V: Task implementation")
> Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> 
> [...]

Here is the summary with links:
  - riscv: process: fix kernel info leakage
    https://git.kernel.org/riscv/c/6510c78490c4

You are awesome, thank you!
-- 
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html