[Qemu-devel] [PATCH] fix read() and acct() on NULL arguments

[Qemu-devel] [PATCH] fix read() and acct() on NULL arguments

[Riku Voipio]

Returning efault in these cases is not correct. Originally
proposed by Thayne Harbaugh in 2007:

http://www.mail-archive.com/qemu-devel@nongnu.org/msg14658.html

Signed-off-by: Riku Voipio <riku.voipio@iki.fi>
---
 linux-user/syscall.c |   24 ++++++++++++++++--------
 1 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index 4eb003a..ab81b3a 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -3713,10 +3713,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         ret = 0; /* avoid warning */
         break;
     case TARGET_NR_read:
-        if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
-            goto efault;
-        ret = get_errno(read(arg1, p, arg3));
-        unlock_user(p, arg2, ret);
+        if (arg3 == 0)
+            ret = 0;
+        else {
+            if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
+                goto efault;
+            ret = get_errno(read(arg1, p, arg3));
+            unlock_user(p, arg2, ret);
+        }
         break;
     case TARGET_NR_write:
         if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
@@ -4217,10 +4221,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
         goto unimplemented;
 #endif
     case TARGET_NR_acct:
-        if (!(p = lock_user_string(arg1)))
-            goto efault;
-        ret = get_errno(acct(path(p)));
-        unlock_user(p, arg1, 0);
+        if (arg1 == 0) {
+            ret = get_errno(acct(NULL));
+        } else {
+            if (!(p = lock_user_string(arg1)))
+                goto efault;
+            ret = get_errno(acct(path(p)));
+            unlock_user(p, arg1, 0);
+        }
         break;
 #ifdef TARGET_NR_umount2 /* not on alpha */
     case TARGET_NR_umount2:
-- 
1.5.6.5


-- 
"rm -rf" only sounds scary if you don't have backups

Re: [Qemu-devel] [PATCH] fix read() and acct() on NULL arguments

[Aurelien Jarno]

On Mon, Jan 19, 2009 at 05:29:12PM +0200, Riku Voipio wrote:
> Returning efault in these cases is not correct. Originally
> proposed by Thayne Harbaugh in 2007:
> 
> http://www.mail-archive.com/qemu-devel@nongnu.org/msg14658.html
> 
> Signed-off-by: Riku Voipio <riku.voipio@iki.fi>

Thanks, applied.

> ---
>  linux-user/syscall.c |   24 ++++++++++++++++--------
>  1 files changed, 16 insertions(+), 8 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index 4eb003a..ab81b3a 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -3713,10 +3713,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>          ret = 0; /* avoid warning */
>          break;
>      case TARGET_NR_read:
> -        if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
> -            goto efault;
> -        ret = get_errno(read(arg1, p, arg3));
> -        unlock_user(p, arg2, ret);
> +        if (arg3 == 0)
> +            ret = 0;
> +        else {
> +            if (!(p = lock_user(VERIFY_WRITE, arg2, arg3, 0)))
> +                goto efault;
> +            ret = get_errno(read(arg1, p, arg3));
> +            unlock_user(p, arg2, ret);
> +        }
>          break;
>      case TARGET_NR_write:
>          if (!(p = lock_user(VERIFY_READ, arg2, arg3, 1)))
> @@ -4217,10 +4221,14 @@ abi_long do_syscall(void *cpu_env, int num, abi_long arg1,
>          goto unimplemented;
>  #endif
>      case TARGET_NR_acct:
> -        if (!(p = lock_user_string(arg1)))
> -            goto efault;
> -        ret = get_errno(acct(path(p)));
> -        unlock_user(p, arg1, 0);
> +        if (arg1 == 0) {
> +            ret = get_errno(acct(NULL));
> +        } else {
> +            if (!(p = lock_user_string(arg1)))
> +                goto efault;
> +            ret = get_errno(acct(path(p)));
> +            unlock_user(p, arg1, 0);
> +        }
>          break;
>  #ifdef TARGET_NR_umount2 /* not on alpha */
>      case TARGET_NR_umount2:
> -- 
> 1.5.6.5
> 
> 
> -- 
> "rm -rf" only sounds scary if you don't have backups
> 
> 
> 

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net