[PATCH 1/4] lib/mpi: only require buffers as big as needed for the integer

[Andrew Zaborowski]

Since mpi_write_to_sgl and mpi_read_buffer explicitly left-align the
integers being written it makes no sense to require a buffer big enough for
the number + the leading zero bytes which are not written.  The error
returned also doesn't convey any information.  So instead require only the
size needed and return -EOVERFLOW to signal when buffer too short.

Signed-off-by: Andrew Zaborowski 
---
 lib/mpi/mpicoder.c | 21 +
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index c7e0a70..074d2df 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -135,7 +135,9 @@ EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
  * @buf:   bufer to which the output will be written to. Needs to be at
  * leaset mpi_get_size(a) long.
  * @buf_len:   size of the buf.
- * @nbytes:receives the actual length of the data written.
+ * @nbytes:receives the actual length of the data written on success and
+ * the data to-be-written on -EOVERFLOW in case buf_len was too
+ * small.
  * @sign:  if not NULL, it will be set to the sign of a.
  *
  * Return: 0 on success or error code in case of error
@@ -148,7 +150,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, 
unsigned *nbytes,
unsigned int n = mpi_get_size(a);
int i, lzeros = 0;
 
-   if (buf_len < n || !buf || !nbytes)
+   if (!buf || !nbytes)
return -EINVAL;
 
if (sign)
@@ -163,6 +165,11 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, 
unsigned *nbytes,
break;
}
 
+   if (buf_len < n - lzeros) {
+   *nbytes = n - lzeros;
+   return -EOVERFLOW;
+   }
+
p = buf;
*nbytes = n - lzeros;
 
@@ -332,7 +339,8 @@ EXPORT_SYMBOL_GPL(mpi_set_buffer);
  * @nbytes:in/out param - it has the be set to the maximum number of
  * bytes that can be written to sgl. This has to be at least
  * the size of the integer a. On return it receives the actual
- * length of the data written.
+ * length of the data written on success or the data that would
+ * be written if buffer was too small.
  * @sign:  if not NULL, it will be set to the sign of a.
  *
  * Return: 0 on success or error code in case of error
@@ -345,7 +353,7 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, 
unsigned *nbytes,
unsigned int n = mpi_get_size(a);
int i, x, y = 0, lzeros = 0, buf_len;
 
-   if (!nbytes || *nbytes < n)
+   if (!nbytes)
return -EINVAL;
 
if (sign)
@@ -360,6 +368,11 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, 
unsigned *nbytes,
break;
}
 
+   if (*nbytes < n - lzeros) {
+   *nbytes = n - lzeros;
+   return -EOVERFLOW;
+   }
+
*nbytes = n - lzeros;
buf_len = sgl->length;
p2 = sg_virt(sgl);
-- 
2.1.4

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Re: [PATCH 1/4] lib/mpi: only require buffers as big as needed for the integer

[Andrzej Zaborowski]

Hi Stephan,

On 13 November 2015 at 13:47, Stephan Mueller  wrote:
> Sorry to be picky here, but is this v2? If yes, may I ask (at least for the
> future) for brief notation of the changes as well as a marking of the patches.

There are no changes in patches 1-3, I wasn't sure if it was okay to
resend just that one patch that was affected.  I'll include some
indication of that next time for the clients that don't make it
apparent that a message is a plain resend.

Best regards
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Re: [PATCH 1/4] lib/mpi: only require buffers as big as needed for the integer

[Stephan Mueller]

Am Freitag, 13. November 2015, 12:01:32 schrieb Andrew Zaborowski:

Hi Andrew,

>Since mpi_write_to_sgl and mpi_read_buffer explicitly left-align the
>integers being written it makes no sense to require a buffer big enough for
>the number + the leading zero bytes which are not written.  The error
>returned also doesn't convey any information.  So instead require only the
>size needed and return -EOVERFLOW to signal when buffer too short.

Sorry to be picky here, but is this v2? If yes, may I ask (at least for the 
future) for brief notation of the changes as well as a marking of the patches.

Ciao
Stephan
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[PATCH 1/4] lib/mpi: only require buffers as big as needed for the integer

[Andrew Zaborowski]

Since mpi_write_to_sgl and mpi_read_buffer explicitly left-align the
integers being written it makes no sense to require a buffer big enough for
the number + the leading zero bytes which are not written.  The error
returned also doesn't convey any information.  So instead require only the
size needed and return -EOVERFLOW to signal when buffer too short.

Signed-off-by: Andrew Zaborowski 
---
 lib/mpi/mpicoder.c | 21 +
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/lib/mpi/mpicoder.c b/lib/mpi/mpicoder.c
index c7e0a70..074d2df 100644
--- a/lib/mpi/mpicoder.c
+++ b/lib/mpi/mpicoder.c
@@ -135,7 +135,9 @@ EXPORT_SYMBOL_GPL(mpi_read_from_buffer);
  * @buf:   bufer to which the output will be written to. Needs to be at
  * leaset mpi_get_size(a) long.
  * @buf_len:   size of the buf.
- * @nbytes:receives the actual length of the data written.
+ * @nbytes:receives the actual length of the data written on success and
+ * the data to-be-written on -EOVERFLOW in case buf_len was too
+ * small.
  * @sign:  if not NULL, it will be set to the sign of a.
  *
  * Return: 0 on success or error code in case of error
@@ -148,7 +150,7 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, 
unsigned *nbytes,
unsigned int n = mpi_get_size(a);
int i, lzeros = 0;
 
-   if (buf_len < n || !buf || !nbytes)
+   if (!buf || !nbytes)
return -EINVAL;
 
if (sign)
@@ -163,6 +165,11 @@ int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, 
unsigned *nbytes,
break;
}
 
+   if (buf_len < n - lzeros) {
+   *nbytes = n - lzeros;
+   return -EOVERFLOW;
+   }
+
p = buf;
*nbytes = n - lzeros;
 
@@ -332,7 +339,8 @@ EXPORT_SYMBOL_GPL(mpi_set_buffer);
  * @nbytes:in/out param - it has the be set to the maximum number of
  * bytes that can be written to sgl. This has to be at least
  * the size of the integer a. On return it receives the actual
- * length of the data written.
+ * length of the data written on success or the data that would
+ * be written if buffer was too small.
  * @sign:  if not NULL, it will be set to the sign of a.
  *
  * Return: 0 on success or error code in case of error
@@ -345,7 +353,7 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, 
unsigned *nbytes,
unsigned int n = mpi_get_size(a);
int i, x, y = 0, lzeros = 0, buf_len;
 
-   if (!nbytes || *nbytes < n)
+   if (!nbytes)
return -EINVAL;
 
if (sign)
@@ -360,6 +368,11 @@ int mpi_write_to_sgl(MPI a, struct scatterlist *sgl, 
unsigned *nbytes,
break;
}
 
+   if (*nbytes < n - lzeros) {
+   *nbytes = n - lzeros;
+   return -EOVERFLOW;
+   }
+
*nbytes = n - lzeros;
buf_len = sgl->length;
p2 = sg_virt(sgl);
-- 
2.1.4

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