[Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Kevin Wolf]

scanf calls must not use PRI constants, they have probably the wrong size and
corrupt memory. We could replace them by SCN ones, but strtol is simpler than
scanf here anyway. While at it, also fix the parsers to reject garbage after
the number ("4096xyz" was accepted before).

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 hw/qdev-properties.c |   50 +++++++++++++++++++++++++++++++++++---------------
 1 files changed, 35 insertions(+), 15 deletions(-)

diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
index 9ffdba7..9a61ca2 100644
--- a/hw/qdev-properties.c
+++ b/hw/qdev-properties.c
@@ -68,12 +68,14 @@ PropertyInfo qdev_prop_bit = {
 static int parse_uint8(DeviceState *dev, Property *prop, const char *str)
 {
     uint8_t *ptr = qdev_get_prop_ptr(dev, prop);
-    const char *fmt;
+    char *end;
 
     /* accept both hex and decimal */
-    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx8 : "%" PRIu8;
-    if (sscanf(str, fmt, ptr) != 1)
+    *ptr = strtoul(str, &end, 0);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -96,12 +98,14 @@ PropertyInfo qdev_prop_uint8 = {
 static int parse_uint16(DeviceState *dev, Property *prop, const char *str)
 {
     uint16_t *ptr = qdev_get_prop_ptr(dev, prop);
-    const char *fmt;
+    char *end;
 
     /* accept both hex and decimal */
-    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx16 : "%" PRIu16;
-    if (sscanf(str, fmt, ptr) != 1)
+    *ptr = strtoul(str, &end, 0);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -124,12 +128,14 @@ PropertyInfo qdev_prop_uint16 = {
 static int parse_uint32(DeviceState *dev, Property *prop, const char *str)
 {
     uint32_t *ptr = qdev_get_prop_ptr(dev, prop);
-    const char *fmt;
+    char *end;
 
     /* accept both hex and decimal */
-    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx32 : "%" PRIu32;
-    if (sscanf(str, fmt, ptr) != 1)
+    *ptr = strtoul(str, &end, 0);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -150,9 +156,13 @@ PropertyInfo qdev_prop_uint32 = {
 static int parse_int32(DeviceState *dev, Property *prop, const char *str)
 {
     int32_t *ptr = qdev_get_prop_ptr(dev, prop);
+    char *end;
 
-    if (sscanf(str, "%" PRId32, ptr) != 1)
+    *ptr = strtol(str, &end, 10);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -175,9 +185,13 @@ PropertyInfo qdev_prop_int32 = {
 static int parse_hex32(DeviceState *dev, Property *prop, const char *str)
 {
     uint32_t *ptr = qdev_get_prop_ptr(dev, prop);
+    char *end;
 
-    if (sscanf(str, "%" PRIx32, ptr) != 1)
+    *ptr = strtoul(str, &end, 16);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -200,12 +214,14 @@ PropertyInfo qdev_prop_hex32 = {
 static int parse_uint64(DeviceState *dev, Property *prop, const char *str)
 {
     uint64_t *ptr = qdev_get_prop_ptr(dev, prop);
-    const char *fmt;
+    char *end;
 
     /* accept both hex and decimal */
-    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx64 : "%" PRIu64;
-    if (sscanf(str, fmt, ptr) != 1)
+    *ptr = strtoull(str, &end, 0);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
@@ -228,9 +244,13 @@ PropertyInfo qdev_prop_uint64 = {
 static int parse_hex64(DeviceState *dev, Property *prop, const char *str)
 {
     uint64_t *ptr = qdev_get_prop_ptr(dev, prop);
+    char *end;
 
-    if (sscanf(str, "%" PRIx64, ptr) != 1)
+    *ptr = strtoull(str, &end, 16);
+    if (end != str + strlen(str)) {
         return -EINVAL;
+    }
+
     return 0;
 }
 
-- 
1.6.6.1

Re: [Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Daniel P. Berrange]

On Wed, May 26, 2010 at 12:28:13PM +0200, Kevin Wolf wrote:
> scanf calls must not use PRI constants, they have probably the wrong size and
> corrupt memory. We could replace them by SCN ones, but strtol is simpler than
> scanf here anyway. While at it, also fix the parsers to reject garbage after
> the number ("4096xyz" was accepted before).
> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  hw/qdev-properties.c |   50 +++++++++++++++++++++++++++++++++++---------------
>  1 files changed, 35 insertions(+), 15 deletions(-)
> 
> diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
> index 9ffdba7..9a61ca2 100644
> --- a/hw/qdev-properties.c
> +++ b/hw/qdev-properties.c
> @@ -68,12 +68,14 @@ PropertyInfo qdev_prop_bit = {
>  static int parse_uint8(DeviceState *dev, Property *prop, const char *str)
>  {
>      uint8_t *ptr = qdev_get_prop_ptr(dev, prop);
> -    const char *fmt;
> +    char *end;
>  
>      /* accept both hex and decimal */
> -    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx8 : "%" PRIu8;
> -    if (sscanf(str, fmt, ptr) != 1)
> +    *ptr = strtoul(str, &end, 0);
> +    if (end != str + strlen(str)) {
>          return -EINVAL;
> +    }

I think you can avoid the O(n) operation here & in the other cases with
a test like this:

    if ((end == str) || (*end != '\0'))
       return -EINVAL

Regards,
Daniel
-- 
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Re: [Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Kevin Wolf]

Am 26.05.2010 12:45, schrieb Daniel P. Berrange:
> On Wed, May 26, 2010 at 12:28:13PM +0200, Kevin Wolf wrote:
>> scanf calls must not use PRI constants, they have probably the wrong size and
>> corrupt memory. We could replace them by SCN ones, but strtol is simpler than
>> scanf here anyway. While at it, also fix the parsers to reject garbage after
>> the number ("4096xyz" was accepted before).
>>
>> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
>> ---
>>  hw/qdev-properties.c |   50 +++++++++++++++++++++++++++++++++++---------------
>>  1 files changed, 35 insertions(+), 15 deletions(-)
>>
>> diff --git a/hw/qdev-properties.c b/hw/qdev-properties.c
>> index 9ffdba7..9a61ca2 100644
>> --- a/hw/qdev-properties.c
>> +++ b/hw/qdev-properties.c
>> @@ -68,12 +68,14 @@ PropertyInfo qdev_prop_bit = {
>>  static int parse_uint8(DeviceState *dev, Property *prop, const char *str)
>>  {
>>      uint8_t *ptr = qdev_get_prop_ptr(dev, prop);
>> -    const char *fmt;
>> +    char *end;
>>  
>>      /* accept both hex and decimal */
>> -    fmt = strncasecmp(str, "0x",2) == 0 ? "%" PRIx8 : "%" PRIu8;
>> -    if (sscanf(str, fmt, ptr) != 1)
>> +    *ptr = strtoul(str, &end, 0);
>> +    if (end != str + strlen(str)) {
>>          return -EINVAL;
>> +    }
> 
> I think you can avoid the O(n) operation here & in the other cases with
> a test like this:
> 
>     if ((end == str) || (*end != '\0'))
>        return -EINVAL

It probably doesn't really make a difference here, but you're right.
I'll send another version with this change.

Kevin

Re: [Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Markus Armbruster]

Kevin Wolf <kwolf@redhat.com> writes:

> scanf calls must not use PRI constants, they have probably the wrong size and
> corrupt memory. We could replace them by SCN ones, but strtol is simpler than
> scanf here anyway. While at it, also fix the parsers to reject garbage after
> the number ("4096xyz" was accepted before).

Do we have more misuse of PRI with scanf elsewhere?  No need to fix them
all in one commit (and thus delay this fix); I just want to make sure
somebody looks.

Re: [Qemu-devel] [PATCH] qdev-properties: Fix (u)intXX parsers

[Kevin Wolf]

Am 26.05.2010 13:13, schrieb Markus Armbruster:
> Kevin Wolf <kwolf@redhat.com> writes:
> 
>> scanf calls must not use PRI constants, they have probably the wrong size and
>> corrupt memory. We could replace them by SCN ones, but strtol is simpler than
>> scanf here anyway. While at it, also fix the parsers to reject garbage after
>> the number ("4096xyz" was accepted before).
> 
> Do we have more misuse of PRI with scanf elsewhere?  No need to fix them
> all in one commit (and thus delay this fix); I just want to make sure
> somebody looks.

I saw another one in some Xen file that Gerd should fix some time. I'm
not aware of any other.

Kevin