1. Patchew
  2. EDK2
  3. [edk2] [PATCH v3 0/6] Refine type cast for pointer subtraction
  4. View patch

[edk2] [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction

Hao Wu posted 6 patches 7 years, 8 months ago
[edk2] [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction
Posted by Hao Wu 7 years, 8 months ago 
For pointer subtraction, the result is of type "ptrdiff_t". According to
the C11 standard (Committee Draft - April 12, 2011):

"When two pointers are subtracted, both shall point to elements of the
same array object, or one past the last element of the array object; the
result is the difference of the subscripts of the two array elements. The
size of the result is implementation-defined, and its type (a signed
integer type) is ptrdiff_t defined in the <stddef.h> header. If the result
is not representable in an object of that type, the behavior is
undefined."

In our codes, there are cases that the pointer subtraction is not
performed by pointers to elements of the same array object. This might
lead to potential issues, since the behavior is undefined according to C11
standard.

Also, since the size of type "ptrdiff_t" is implementation-defined. Some
static code checkers may warn that the pointer subtraction might underflow
first and then being cast to a bigger size. For example:

UINT8  *Ptr1, *Ptr2;
UINTN  PtrDiff;
...
PtrDiff = (UINTN) (Ptr1 - Ptr2);

The commit will refine the pointer subtraction expressions by casting each
pointer to UINTN first and then perform the subtraction:

PtrDiff = (UINTN) Ptr1 - (UINTN) Ptr2;

Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
---
 NetworkPkg/HttpDxe/HttpImpl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/NetworkPkg/HttpDxe/HttpImpl.c b/NetworkPkg/HttpDxe/HttpImpl.c
index 745832b..1f7a4fa 100644
--- a/NetworkPkg/HttpDxe/HttpImpl.c
+++ b/NetworkPkg/HttpDxe/HttpImpl.c
@@ -1342,7 +1342,7 @@ HttpResponseWorker (
     // We receive part of header of next HTTP msg.
     //
     if (HttpInstance->NextMsg != NULL) {
-      HttpMsg->BodyLength = MIN ((UINTN) (HttpInstance->NextMsg - (CHAR8 *) Fragment.Bulk), HttpMsg->BodyLength);
+      HttpMsg->BodyLength = MIN ((UINTN) HttpInstance->NextMsg - (UINTN) Fragment.Bulk, HttpMsg->BodyLength);
       CopyMem (HttpMsg->Body, Fragment.Bulk, HttpMsg->BodyLength);
       
       HttpInstance->CacheLen = Fragment.Len - HttpMsg->BodyLength;
@@ -1360,7 +1360,7 @@ HttpResponseWorker (
         CopyMem (HttpInstance->CacheBody, Fragment.Bulk + HttpMsg->BodyLength, HttpInstance->CacheLen);
         HttpInstance->CacheOffset = 0;
 
-        HttpInstance->NextMsg = HttpInstance->CacheBody + (UINTN) (HttpInstance->NextMsg - (CHAR8 *) (Fragment.Bulk + HttpMsg->BodyLength));
+        HttpInstance->NextMsg = HttpInstance->CacheBody + ((UINTN) HttpInstance->NextMsg - (UINTN) (Fragment.Bulk + HttpMsg->BodyLength));
       }
     } else {
       HttpMsg->BodyLength = MIN (Fragment.Len, (UINT32) HttpMsg->BodyLength);
-- 
1.9.5.msysgit.0

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction
Posted by Fu, Siyuan 7 years, 8 months ago 
Reviewed-by: Fu Siyuan <siyuan.fu@intel.com>


-----Original Message-----
From: Wu, Hao A 
Sent: 2017年2月25日 12:05
To: edk2-devel@lists.01.org
Cc: Wu, Hao A <hao.a.wu@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>; Wu, Jiaxin <jiaxin.wu@intel.com>
Subject: [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction

For pointer subtraction, the result is of type "ptrdiff_t". According to the C11 standard (Committee Draft - April 12, 2011):

"When two pointers are subtracted, both shall point to elements of the same array object, or one past the last element of the array object; the result is the difference of the subscripts of the two array elements. The size of the result is implementation-defined, and its type (a signed integer type) is ptrdiff_t defined in the <stddef.h> header. If the result is not representable in an object of that type, the behavior is undefined."

In our codes, there are cases that the pointer subtraction is not performed by pointers to elements of the same array object. This might lead to potential issues, since the behavior is undefined according to C11 standard.

Also, since the size of type "ptrdiff_t" is implementation-defined. Some static code checkers may warn that the pointer subtraction might underflow first and then being cast to a bigger size. For example:

UINT8  *Ptr1, *Ptr2;
UINTN  PtrDiff;
...
PtrDiff = (UINTN) (Ptr1 - Ptr2);

The commit will refine the pointer subtraction expressions by casting each pointer to UINTN first and then perform the subtraction:

PtrDiff = (UINTN) Ptr1 - (UINTN) Ptr2;

Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Hao Wu <hao.a.wu@intel.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
---
 NetworkPkg/HttpDxe/HttpImpl.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/NetworkPkg/HttpDxe/HttpImpl.c b/NetworkPkg/HttpDxe/HttpImpl.c index 745832b..1f7a4fa 100644
--- a/NetworkPkg/HttpDxe/HttpImpl.c
+++ b/NetworkPkg/HttpDxe/HttpImpl.c
@@ -1342,7 +1342,7 @@ HttpResponseWorker (
     // We receive part of header of next HTTP msg.
     //
     if (HttpInstance->NextMsg != NULL) {
-      HttpMsg->BodyLength = MIN ((UINTN) (HttpInstance->NextMsg - (CHAR8 *) Fragment.Bulk), HttpMsg->BodyLength);
+      HttpMsg->BodyLength = MIN ((UINTN) HttpInstance->NextMsg - 
+ (UINTN) Fragment.Bulk, HttpMsg->BodyLength);
       CopyMem (HttpMsg->Body, Fragment.Bulk, HttpMsg->BodyLength);
       
       HttpInstance->CacheLen = Fragment.Len - HttpMsg->BodyLength; @@ -1360,7 +1360,7 @@ HttpResponseWorker (
         CopyMem (HttpInstance->CacheBody, Fragment.Bulk + HttpMsg->BodyLength, HttpInstance->CacheLen);
         HttpInstance->CacheOffset = 0;
 
-        HttpInstance->NextMsg = HttpInstance->CacheBody + (UINTN) (HttpInstance->NextMsg - (CHAR8 *) (Fragment.Bulk + HttpMsg->BodyLength));
+        HttpInstance->NextMsg = HttpInstance->CacheBody + ((UINTN) 
+ HttpInstance->NextMsg - (UINTN) (Fragment.Bulk + 
+ HttpMsg->BodyLength));
       }
     } else {
       HttpMsg->BodyLength = MIN (Fragment.Len, (UINT32) HttpMsg->BodyLength);
--
1.9.5.msysgit.0

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
Re: [edk2] [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction
Posted by Wu, Jiaxin 7 years, 8 months ago 
Reviewed-by: Wu Jiaxin <jiaxin.wu@intel.com>


> -----Original Message-----
> From: Wu, Hao A
> Sent: Saturday, February 25, 2017 12:05 PM
> To: edk2-devel@lists.01.org
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Fu, Siyuan <siyuan.fu@intel.com>;
> Wu, Jiaxin <jiaxin.wu@intel.com>
> Subject: [PATCH v3 4/6] NetworkPkg: Refine type cast for pointer subtraction
> 
> For pointer subtraction, the result is of type "ptrdiff_t". According to
> the C11 standard (Committee Draft - April 12, 2011):
> 
> "When two pointers are subtracted, both shall point to elements of the
> same array object, or one past the last element of the array object; the
> result is the difference of the subscripts of the two array elements. The
> size of the result is implementation-defined, and its type (a signed
> integer type) is ptrdiff_t defined in the <stddef.h> header. If the result
> is not representable in an object of that type, the behavior is
> undefined."
> 
> In our codes, there are cases that the pointer subtraction is not
> performed by pointers to elements of the same array object. This might
> lead to potential issues, since the behavior is undefined according to C11
> standard.
> 
> Also, since the size of type "ptrdiff_t" is implementation-defined. Some
> static code checkers may warn that the pointer subtraction might underflow
> first and then being cast to a bigger size. For example:
> 
> UINT8  *Ptr1, *Ptr2;
> UINTN  PtrDiff;
> ...
> PtrDiff = (UINTN) (Ptr1 - Ptr2);
> 
> The commit will refine the pointer subtraction expressions by casting each
> pointer to UINTN first and then perform the subtraction:
> 
> PtrDiff = (UINTN) Ptr1 - (UINTN) Ptr2;
> 
> Cc: Siyuan Fu <siyuan.fu@intel.com>
> Cc: Jiaxin Wu <jiaxin.wu@intel.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Hao Wu <hao.a.wu@intel.com>
> Acked-by: Laszlo Ersek <lersek@redhat.com>
> ---
>  NetworkPkg/HttpDxe/HttpImpl.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/NetworkPkg/HttpDxe/HttpImpl.c
> b/NetworkPkg/HttpDxe/HttpImpl.c
> index 745832b..1f7a4fa 100644
> --- a/NetworkPkg/HttpDxe/HttpImpl.c
> +++ b/NetworkPkg/HttpDxe/HttpImpl.c
> @@ -1342,7 +1342,7 @@ HttpResponseWorker (
>      // We receive part of header of next HTTP msg.
>      //
>      if (HttpInstance->NextMsg != NULL) {
> -      HttpMsg->BodyLength = MIN ((UINTN) (HttpInstance->NextMsg -
> (CHAR8 *) Fragment.Bulk), HttpMsg->BodyLength);
> +      HttpMsg->BodyLength = MIN ((UINTN) HttpInstance->NextMsg -
> (UINTN) Fragment.Bulk, HttpMsg->BodyLength);
>        CopyMem (HttpMsg->Body, Fragment.Bulk, HttpMsg->BodyLength);
> 
>        HttpInstance->CacheLen = Fragment.Len - HttpMsg->BodyLength;
> @@ -1360,7 +1360,7 @@ HttpResponseWorker (
>          CopyMem (HttpInstance->CacheBody, Fragment.Bulk + HttpMsg-
> >BodyLength, HttpInstance->CacheLen);
>          HttpInstance->CacheOffset = 0;
> 
> -        HttpInstance->NextMsg = HttpInstance->CacheBody + (UINTN)
> (HttpInstance->NextMsg - (CHAR8 *) (Fragment.Bulk + HttpMsg-
> >BodyLength));
> +        HttpInstance->NextMsg = HttpInstance->CacheBody + ((UINTN)
> HttpInstance->NextMsg - (UINTN) (Fragment.Bulk + HttpMsg->BodyLength));
>        }
>      } else {
>        HttpMsg->BodyLength = MIN (Fragment.Len, (UINT32) HttpMsg-
> >BodyLength);
> --
> 1.9.5.msysgit.0

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel

Patchew 2.1-devel-b67e4c2

© 2016 - 2024 Red Hat, Inc.