Re: [LTP] [PATCH] sendfile08 - initialize buf structure

[Jan Stancek <jstancek@redhat.com>]

----- Original Message -----
> From: "Helge Deller" <deller@gmx.de>
> To: ltp-list@lists.sourceforge.net
> Sent: Wednesday, 6 November, 2013 8:41:11 PM
> Subject: [LTP] [PATCH] sendfile08 - initialize buf structure
> 
> The sendfile08 testcase uses the sendfile() syscall
> to write the strings "hello" and "world" to a file descriptor
> and then reads them back in through another file descriptor.
> 
> The length of the strings written are determined by strlen(),
> so that in total 10 bytes are written.
> 
> When reading the strings back in, again 10 bytes are read, but
> the problem is, that those are read back into a *local* string
> buffer array (buf[]) which hasn't been initialized.
> 
> Afterwards,
>   strcmp(buf, "helloworld")
> is called to compare input and output.
> This strcmp() is wrong, because basically "helloworld\0"
> (with the trailing string zero terminator) is compared to
> "helloworld" (likely without a trailing zero in the buf[] array).
> 
> So, if buf[] hasn't been initialized, it's not guaranteed
> that the 10th byte in buf[10] equals to '\0'.
> 
> This problem was found on hppa64-linux-gnu architecture, most
> likely, because it's a stack-grows-up architecture.
> 
> Fix this buglet, by zero-initializing the buf[] array.
> Alternatively, strncmp() could be used instead of memcmp().
> 
> Signed-off-by: Helge Deller <deller@gmx.de>

Hi,

I pushed the strncmp() version.

Thanks,
Jan

> 
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