[PATCH v2] xfsprogs: fix wrong variable type in write_once function

[PATCH v2] xfsprogs: fix wrong variable type in write_once function

[Zorro Lang]

The 'Coverity Scan' found a problem in new write_once() function:

272             size_t bytes;
273             bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
>>>     CID 1420710:  Control flow issues  (NO_EFFECT)
>>>     This less-than-zero comparison of an unsigned value is never true. "bytes < 0UL".
274             if (bytes < 0)
275                     return -1;

That's unreasonable. do_pwrite return 'ssize_t' type value, which can
be less than zero, but we use a 'size_t' to get the return value. So
change the size_t to ssize_t for it can store the return value
correctly.

By the chance, correct all 'ssize_t' type problems in pwrite related
functions.

Signed-off-by: Zorro Lang <zlang@redhat.com>
---

V2 changed more than V1, as below:
1) The return value type of do_pwritev and do_pwrite, from 'int' to 'ssize_t'
2) The arguments type of do_pwritev and do_pwrite, from 'ssize_t' to 'size_t'

Thanks,
Zorro

 io/pwrite.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/io/pwrite.c b/io/pwrite.c
index 26f79579..3df976a8 100644
--- a/io/pwrite.c
+++ b/io/pwrite.c
@@ -61,12 +61,12 @@ pwrite_help(void)
 }
 
 #ifdef HAVE_PWRITEV
-static int
+static ssize_t
 do_pwritev(
 	int		fd,
 	off64_t		offset,
-	ssize_t		count,
-	ssize_t		buffer_size,
+	size_t		count,
+	size_t		buffer_size,
 	int 		pwritev2_flags)
 {
 	int vecs = 0;
@@ -105,12 +105,12 @@ do_pwritev(
 #define do_pwritev(fd, offset, count, buffer_size) (0)
 #endif
 
-static int
+static ssize_t
 do_pwrite(
 	int		fd,
 	off64_t		offset,
-	ssize_t		count,
-	ssize_t		buffer_size,
+	size_t		count,
+	size_t		buffer_size,
 	int		pwritev2_flags)
 {
 	if (!vectors)
@@ -269,7 +269,7 @@ write_once(
 	long long	*total,
 	int		pwritev2_flags)
 {
-	size_t bytes;
+	ssize_t bytes;
 	bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
 	if (bytes < 0)
 		return -1;
-- 
2.13.6

Re: [PATCH v2] xfsprogs: fix wrong variable type in write_once function

[Eric Sandeen]

On 11/11/17 7:57 AM, Zorro Lang wrote:
> The 'Coverity Scan' found a problem in new write_once() function:
> 
> 272             size_t bytes;
> 273             bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
>>>>     CID 1420710:  Control flow issues  (NO_EFFECT)
>>>>     This less-than-zero comparison of an unsigned value is never true. "bytes < 0UL".
> 274             if (bytes < 0)
> 275                     return -1;
> 
> That's unreasonable. do_pwrite return 'ssize_t' type value, which can
> be less than zero, but we use a 'size_t' to get the return value. So
> change the size_t to ssize_t for it can store the return value
> correctly.
> 
> By the chance, correct all 'ssize_t' type problems in pwrite related
> functions.
> 
> Signed-off-by: Zorro Lang <zlang@redhat.com>
> ---
> 
> V2 changed more than V1, as below:
> 1) The return value type of do_pwritev and do_pwrite, from 'int' to 'ssize_t'
> 2) The arguments type of do_pwritev and do_pwrite, from 'ssize_t' to 'size_t'
> 
> Thanks,
> Zorro
> 
>  io/pwrite.c | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/io/pwrite.c b/io/pwrite.c
> index 26f79579..3df976a8 100644
> --- a/io/pwrite.c
> +++ b/io/pwrite.c
> @@ -61,12 +61,12 @@ pwrite_help(void)
>  }
>  
>  #ifdef HAVE_PWRITEV
> -static int
> +static ssize_t
>  do_pwritev(
>  	int		fd,
>  	off64_t		offset,
> -	ssize_t		count,
> -	ssize_t		buffer_size,
> +	size_t		count,
> +	size_t		buffer_size,

I had not noticed this before, but this is odd; buffer_size is not used
in this function. Instead, we test the global "buffersize"

I'm not sure what's going on there, need to read the code bit more.
That's probably a separate fix though.

I think the rest looks ok,

Reviewed-by: Eric Sandeen <sandeen@sandeen.net>



>  	int 		pwritev2_flags)
>  {
>  	int vecs = 0;
> @@ -105,12 +105,12 @@ do_pwritev(
>  #define do_pwritev(fd, offset, count, buffer_size) (0)
>  #endif
>  
> -static int
> +static ssize_t
>  do_pwrite(
>  	int		fd,
>  	off64_t		offset,
> -	ssize_t		count,
> -	ssize_t		buffer_size,
> +	size_t		count,
> +	size_t		buffer_size,
>  	int		pwritev2_flags)
>  {
>  	if (!vectors)
> @@ -269,7 +269,7 @@ write_once(
>  	long long	*total,
>  	int		pwritev2_flags)
>  {
> -	size_t bytes;
> +	ssize_t bytes;
>  	bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
>  	if (bytes < 0)
>  		return -1;

> 

Re: [PATCH v2] xfsprogs: fix wrong variable type in write_once function

[Zorro Lang]

On Sat, Nov 11, 2017 at 09:46:48AM -0600, Eric Sandeen wrote:
> On 11/11/17 7:57 AM, Zorro Lang wrote:
> > The 'Coverity Scan' found a problem in new write_once() function:
> > 
> > 272             size_t bytes;
> > 273             bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
> >>>>     CID 1420710:  Control flow issues  (NO_EFFECT)
> >>>>     This less-than-zero comparison of an unsigned value is never true. "bytes < 0UL".
> > 274             if (bytes < 0)
> > 275                     return -1;
> > 
> > That's unreasonable. do_pwrite return 'ssize_t' type value, which can
> > be less than zero, but we use a 'size_t' to get the return value. So
> > change the size_t to ssize_t for it can store the return value
> > correctly.
> > 
> > By the chance, correct all 'ssize_t' type problems in pwrite related
> > functions.
> > 
> > Signed-off-by: Zorro Lang <zlang@redhat.com>
> > ---
> > 
> > V2 changed more than V1, as below:
> > 1) The return value type of do_pwritev and do_pwrite, from 'int' to 'ssize_t'
> > 2) The arguments type of do_pwritev and do_pwrite, from 'ssize_t' to 'size_t'
> > 
> > Thanks,
> > Zorro
> > 
> >  io/pwrite.c | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > diff --git a/io/pwrite.c b/io/pwrite.c
> > index 26f79579..3df976a8 100644
> > --- a/io/pwrite.c
> > +++ b/io/pwrite.c
> > @@ -61,12 +61,12 @@ pwrite_help(void)
> >  }
> >  
> >  #ifdef HAVE_PWRITEV
> > -static int
> > +static ssize_t
> >  do_pwritev(
> >  	int		fd,
> >  	off64_t		offset,
> > -	ssize_t		count,
> > -	ssize_t		buffer_size,
> > +	size_t		count,
> > +	size_t		buffer_size,
> 
> I had not noticed this before, but this is odd; buffer_size is not used
> in this function. Instead, we test the global "buffersize"
> 
> I'm not sure what's going on there, need to read the code bit more.
> That's probably a separate fix though.

The buffer_size argument in do_pwritev/do_preadv is useless. I'll remove
it in a separate patch. But due to this patch changed the 'buffer_size'
place, I'll send this patch and 'remove buffer_size' patch together.
To prevent merge conflict.

Thanks,
Zorro

> 
> I think the rest looks ok,
> 
> Reviewed-by: Eric Sandeen <sandeen@sandeen.net>
> 
> 
> 
> >  	int 		pwritev2_flags)
> >  {
> >  	int vecs = 0;
> > @@ -105,12 +105,12 @@ do_pwritev(
> >  #define do_pwritev(fd, offset, count, buffer_size) (0)
> >  #endif
> >  
> > -static int
> > +static ssize_t
> >  do_pwrite(
> >  	int		fd,
> >  	off64_t		offset,
> > -	ssize_t		count,
> > -	ssize_t		buffer_size,
> > +	size_t		count,
> > +	size_t		buffer_size,
> >  	int		pwritev2_flags)
> >  {
> >  	if (!vectors)
> > @@ -269,7 +269,7 @@ write_once(
> >  	long long	*total,
> >  	int		pwritev2_flags)
> >  {
> > -	size_t bytes;
> > +	ssize_t bytes;
> >  	bytes = do_pwrite(file->fd, offset, count, count, pwritev2_flags);
> >  	if (bytes < 0)
> >  		return -1;
> 
> > 
> --
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