Linux kernel now checks the read permissions before validating `how`

Suggested-by: Laurent Vivier <laurent@vivier.eu>
Signed-off-by: Patrick Venture <venture@google.com>
---
 linux-user/syscall.c | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 34bd819e38..210483d4e4 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -9465,6 +9465,13 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
             int how;
 
             if (arg2) {
+                p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1));
+                if (!p) {
+                    return -TARGET_EFAULT;
+                }
+                target_to_host_old_sigset(&set, p);
+                unlock_user(p, arg2, 0);
+                set_ptr = &set;
                 switch (arg1) {
                 case TARGET_SIG_BLOCK:
                     how = SIG_BLOCK;
@@ -9478,11 +9485,6 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
                 default:
                     return -TARGET_EINVAL;
                 }
-                if (!(p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1)))
-                    return -TARGET_EFAULT;
-                target_to_host_old_sigset(&set, p);
-                unlock_user(p, arg2, 0);
-                set_ptr = &set;
             } else {
                 how = 0;
                 set_ptr = NULL;
-- 
2.35.0.rc0.227.g00780c9af4-goog

Le 26/01/2022 à 18:58, Patrick Venture a écrit :
> Linux kernel now checks the read permissions before validating `how`
> 
> Suggested-by: Laurent Vivier <laurent@vivier.eu>
> Signed-off-by: Patrick Venture <venture@google.com>

Reviewed-by: Laurent Vivier <laurent@vivier.eu>

> ---
>   linux-user/syscall.c | 12 +++++++-----
>   1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 34bd819e38..210483d4e4 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -9465,6 +9465,13 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
>               int how;
>   
>               if (arg2) {
> +                p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1));
> +                if (!p) {
> +                    return -TARGET_EFAULT;
> +                }
> +                target_to_host_old_sigset(&set, p);
> +                unlock_user(p, arg2, 0);
> +                set_ptr = &set;
>                   switch (arg1) {
>                   case TARGET_SIG_BLOCK:
>                       how = SIG_BLOCK;
> @@ -9478,11 +9485,6 @@ static abi_long do_syscall1(void *cpu_env, int num, abi_long arg1,
>                   default:
>                       return -TARGET_EINVAL;
>                   }
> -                if (!(p = lock_user(VERIFY_READ, arg2, sizeof(target_sigset_t), 1)))
> -                    return -TARGET_EFAULT;
> -                target_to_host_old_sigset(&set, p);
> -                unlock_user(p, arg2, 0);
> -                set_ptr = &set;
>               } else {
>                   how = 0;
>                   set_ptr = NULL;