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Date: Tue, 14 Mar 2017 10:25:49 +0100
From: Kevin Wolf <kwolf@redhat.com>
Message-ID: <20170314092549.GA3952@noname.str.redhat.com>
References: <20170314090922.28083-1-stefanha@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH] file-posix: clean up max_segments buffer
 termination
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To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org, Fam Zheng <famz@redhat.com>

Am 14.03.2017 um 10:09 hat Stefan Hajnoczi geschrieben:
> The following pattern is unsafe:
> 
>   char buf[32];
>   ret = read(fd, buf, sizeof(buf));
>   ...
>   buf[ret] = 0;
> 
> If read(2) returns 32 then a byte beyond the end of the buffer is
> zeroed.
> 
> In practice this buffer overflow does not occur because the sysfs
> max_segments file only contains an unsigned short + '\n'.  The string is
> always shorter than 32 bytes.
> 
> Regardless, avoid this pattern because static analysis tools might
> complain and it could lead to real buffer overflows if copy-pasted
> elsewhere in the codebase.
> 
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

Oops. I should have found this during review. Thanks for catching it.

Thanks, applied to the block branch.

Kevin