[Qemu-devel] [PATCH] linux-user: Fix crashes in ioctl(SIOCGIFCONF) when ifc_buf is NULL.

[Qemu-devel] [PATCH] linux-user: Fix crashes in ioctl(SIOCGIFCONF) when ifc_buf is NULL.

[Kan Li]

Summary:
This is to fix bug https://bugs.launchpad.net/qemu/+bug/1796754.
It is valid for ifc_buf to be NULL according to
http://man7.org/linux/man-pages/man7/netdevice.7.html.

Signed-off-by: Kan Li <likan_999.student@sina.com>
---
 linux-user/syscall.c | 56 ++++++++++++++++++++++++--------------------
 1 file changed, 31 insertions(+), 25 deletions(-)

diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index ae3c0dfef7..fbab98d4f7 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -4134,28 +4134,33 @@ static abi_long do_ioctl_ifconf(const IOCTLEntry *ie, uint8_t *buf_temp,
     unlock_user(argptr, arg, 0);
 
     host_ifconf = (struct ifconf *)(unsigned long)buf_temp;
-    target_ifc_len = host_ifconf->ifc_len;
     target_ifc_buf = (abi_long)(unsigned long)host_ifconf->ifc_buf;
 
-    target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);
-    nb_ifreq = target_ifc_len / target_ifreq_size;
-    host_ifc_len = nb_ifreq * sizeof(struct ifreq);
+    if (target_ifc_buf != 0) {
+        target_ifc_len = host_ifconf->ifc_len;
 
-    outbufsz = sizeof(*host_ifconf) + host_ifc_len;
-    if (outbufsz > MAX_STRUCT_SIZE) {
-        /* We can't fit all the extents into the fixed size buffer.
-         * Allocate one that is large enough and use it instead.
-         */
-        host_ifconf = malloc(outbufsz);
-        if (!host_ifconf) {
-            return -TARGET_ENOMEM;
+        target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);
+        nb_ifreq = target_ifc_len / target_ifreq_size;
+        host_ifc_len = nb_ifreq * sizeof(struct ifreq);
+
+        outbufsz = sizeof(*host_ifconf) + host_ifc_len;
+        if (outbufsz > MAX_STRUCT_SIZE) {
+            /* We can't fit all the extents into the fixed size buffer.
+             * Allocate one that is large enough and use it instead.
+             */
+            host_ifconf = malloc(outbufsz);
+            if (!host_ifconf) {
+                return -TARGET_ENOMEM;
+            }
+            memcpy(host_ifconf, buf_temp, sizeof(*host_ifconf));
+            free_buf = 1;
         }
-        memcpy(host_ifconf, buf_temp, sizeof(*host_ifconf));
-        free_buf = 1;
-    }
-    host_ifc_buf = (char*)host_ifconf + sizeof(*host_ifconf);
+        host_ifc_buf = (char*)host_ifconf + sizeof(*host_ifconf);
 
-    host_ifconf->ifc_len = host_ifc_len;
+        host_ifconf->ifc_len = host_ifc_len;
+    } else {
+      host_ifc_buf = NULL;
+    }
     host_ifconf->ifc_buf = host_ifc_buf;
 
     ret = get_errno(safe_ioctl(fd, ie->host_cmd, host_ifconf));
@@ -4178,15 +4183,16 @@ static abi_long do_ioctl_ifconf(const IOCTLEntry *ie, uint8_t *buf_temp,
         thunk_convert(argptr, host_ifconf, arg_type, THUNK_TARGET);
         unlock_user(argptr, arg, target_size);
 
-	/* copy ifreq[] to target user */
-
-        argptr = lock_user(VERIFY_WRITE, target_ifc_buf, target_ifc_len, 0);
-        for (i = 0; i < nb_ifreq ; i++) {
-            thunk_convert(argptr + i * target_ifreq_size,
-                          host_ifc_buf + i * sizeof(struct ifreq),
-                          ifreq_arg_type, THUNK_TARGET);
+        if (target_ifc_buf != 0) {
+            /* copy ifreq[] to target user */
+            argptr = lock_user(VERIFY_WRITE, target_ifc_buf, target_ifc_len, 0);
+            for (i = 0; i < nb_ifreq ; i++) {
+                thunk_convert(argptr + i * target_ifreq_size,
+                              host_ifc_buf + i * sizeof(struct ifreq),
+                              ifreq_arg_type, THUNK_TARGET);
+            }
+            unlock_user(argptr, target_ifc_buf, target_ifc_len);
         }
-        unlock_user(argptr, target_ifc_buf, target_ifc_len);
     }
 
     if (free_buf) {
-- 
2.17.1

Re: [Qemu-devel] [PATCH] linux-user: Fix crashes in ioctl(SIOCGIFCONF) when ifc_buf is NULL.

[Laurent Vivier]

On 09/10/2018 09:45, Kan Li wrote:
> Summary:
> This is to fix bug https://bugs.launchpad.net/qemu/+bug/1796754.
> It is valid for ifc_buf to be NULL according to
> http://man7.org/linux/man-pages/man7/netdevice.7.html.
> 
> Signed-off-by: Kan Li <likan_999.student@sina.com>
> ---
>  linux-user/syscall.c | 56 ++++++++++++++++++++++++--------------------
>  1 file changed, 31 insertions(+), 25 deletions(-)

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

Re: [Qemu-devel] [PATCH] linux-user: Fix crashes in ioctl(SIOCGIFCONF) when ifc_buf is NULL.

[Laurent Vivier]

On 09/10/2018 09:45, Kan Li wrote:
> Summary:
> This is to fix bug https://bugs.launchpad.net/qemu/+bug/1796754.
> It is valid for ifc_buf to be NULL according to
> http://man7.org/linux/man-pages/man7/netdevice.7.html.
> 
> Signed-off-by: Kan Li <likan_999.student@sina.com>
> ---
>  linux-user/syscall.c | 56 ++++++++++++++++++++++++--------------------
>  1 file changed, 31 insertions(+), 25 deletions(-)
> 
> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
> index ae3c0dfef7..fbab98d4f7 100644
> --- a/linux-user/syscall.c
> +++ b/linux-user/syscall.c
> @@ -4134,28 +4134,33 @@ static abi_long do_ioctl_ifconf(const IOCTLEntry *ie, uint8_t *buf_temp,
>      unlock_user(argptr, arg, 0);
>  
>      host_ifconf = (struct ifconf *)(unsigned long)buf_temp;
> -    target_ifc_len = host_ifconf->ifc_len;
>      target_ifc_buf = (abi_long)(unsigned long)host_ifconf->ifc_buf;
>  
> -    target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);
> -    nb_ifreq = target_ifc_len / target_ifreq_size;
> -    host_ifc_len = nb_ifreq * sizeof(struct ifreq);
> +    if (target_ifc_buf != 0) {
> +        target_ifc_len = host_ifconf->ifc_len;
>  
> -    outbufsz = sizeof(*host_ifconf) + host_ifc_len;
> -    if (outbufsz > MAX_STRUCT_SIZE) {
> -        /* We can't fit all the extents into the fixed size buffer.
> -         * Allocate one that is large enough and use it instead.
> -         */
> -        host_ifconf = malloc(outbufsz);
> -        if (!host_ifconf) {
> -            return -TARGET_ENOMEM;
> +        target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);
> +        nb_ifreq = target_ifc_len / target_ifreq_size;
> +        host_ifc_len = nb_ifreq * sizeof(struct ifreq);
> +
> +        outbufsz = sizeof(*host_ifconf) + host_ifc_len;
> +        if (outbufsz > MAX_STRUCT_SIZE) {
> +            /* We can't fit all the extents into the fixed size buffer.
> +             * Allocate one that is large enough and use it instead.
> +             */
> +            host_ifconf = malloc(outbufsz);
> +            if (!host_ifconf) {
> +                return -TARGET_ENOMEM;
> +            }
> +            memcpy(host_ifconf, buf_temp, sizeof(*host_ifconf));
> +            free_buf = 1;
>          }
> -        memcpy(host_ifconf, buf_temp, sizeof(*host_ifconf));
> -        free_buf = 1;
> -    }
> -    host_ifc_buf = (char*)host_ifconf + sizeof(*host_ifconf);
> +        host_ifc_buf = (char*)host_ifconf + sizeof(*host_ifconf);
>  
> -    host_ifconf->ifc_len = host_ifc_len;
> +        host_ifconf->ifc_len = host_ifc_len;
> +    } else {
> +      host_ifc_buf = NULL;
> +    }
>      host_ifconf->ifc_buf = host_ifc_buf;
>  
>      ret = get_errno(safe_ioctl(fd, ie->host_cmd, host_ifconf));
> @@ -4178,15 +4183,16 @@ static abi_long do_ioctl_ifconf(const IOCTLEntry *ie, uint8_t *buf_temp,
>          thunk_convert(argptr, host_ifconf, arg_type, THUNK_TARGET);
>          unlock_user(argptr, arg, target_size);
>  
> -	/* copy ifreq[] to target user */
> -
> -        argptr = lock_user(VERIFY_WRITE, target_ifc_buf, target_ifc_len, 0);
> -        for (i = 0; i < nb_ifreq ; i++) {
> -            thunk_convert(argptr + i * target_ifreq_size,
> -                          host_ifc_buf + i * sizeof(struct ifreq),
> -                          ifreq_arg_type, THUNK_TARGET);
> +        if (target_ifc_buf != 0) {
> +            /* copy ifreq[] to target user */
> +            argptr = lock_user(VERIFY_WRITE, target_ifc_buf, target_ifc_len, 0);
> +            for (i = 0; i < nb_ifreq ; i++) {
> +                thunk_convert(argptr + i * target_ifreq_size,
> +                              host_ifc_buf + i * sizeof(struct ifreq),
> +                              ifreq_arg_type, THUNK_TARGET);
> +            }
> +            unlock_user(argptr, target_ifc_buf, target_ifc_len);
>          }
> -        unlock_user(argptr, target_ifc_buf, target_ifc_len);
>      }
>  
>      if (free_buf) {
> 

Applied to my branch linux-user-for-3.1

Thanks,
Laurent

Re: [Qemu-devel] [PATCH] linux-user: Fix crashes in ioctl(SIOCGIFCONF) when ifc_buf is NULL.

[Laurent Vivier]

On 12/10/2018 21:02, Laurent Vivier wrote:
> On 09/10/2018 09:45, Kan Li wrote:
>> Summary:
>> This is to fix bug https://bugs.launchpad.net/qemu/+bug/1796754.
>> It is valid for ifc_buf to be NULL according to
>> http://man7.org/linux/man-pages/man7/netdevice.7.html.
>>
>> Signed-off-by: Kan Li <likan_999.student@sina.com>
>> ---
>>  linux-user/syscall.c | 56 ++++++++++++++++++++++++--------------------
>>  1 file changed, 31 insertions(+), 25 deletions(-)
>>
>> diff --git a/linux-user/syscall.c b/linux-user/syscall.c
>> index ae3c0dfef7..fbab98d4f7 100644
>> --- a/linux-user/syscall.c
>> +++ b/linux-user/syscall.c
>> @@ -4134,28 +4134,33 @@ static abi_long do_ioctl_ifconf(const IOCTLEntry *ie, uint8_t *buf_temp,
>>      unlock_user(argptr, arg, 0);
>>  
>>      host_ifconf = (struct ifconf *)(unsigned long)buf_temp;
>> -    target_ifc_len = host_ifconf->ifc_len;
>>      target_ifc_buf = (abi_long)(unsigned long)host_ifconf->ifc_buf;
>>  
>> -    target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);
>> -    nb_ifreq = target_ifc_len / target_ifreq_size;
>> -    host_ifc_len = nb_ifreq * sizeof(struct ifreq);
>> +    if (target_ifc_buf != 0) {
>> +        target_ifc_len = host_ifconf->ifc_len;
>>  
>> -    outbufsz = sizeof(*host_ifconf) + host_ifc_len;
>> -    if (outbufsz > MAX_STRUCT_SIZE) {
>> -        /* We can't fit all the extents into the fixed size buffer.
>> -         * Allocate one that is large enough and use it instead.
>> -         */
>> -        host_ifconf = malloc(outbufsz);
>> -        if (!host_ifconf) {
>> -            return -TARGET_ENOMEM;
>> +        target_ifreq_size = thunk_type_size(ifreq_arg_type, 0);

In fact, the target_ifreq_size is used later even if target_ifc_buf is
NULL, so you have to move it out of the "if" body.

Thanks,
Laurent